مروری بر فناوری کاربردی فتوکاتالیست و نانوکاتنالیست
Abstract
مروری بر فناوری کاربردی فتوکاتالیست و نانوکاتنالیست
حسگرها و آپتاحسگرهای الکتروشیمیایی اجـزا، عملکـرد و کاربـرد (مروری بر جدیدترین فناوری¬های ساخت حسگرها و آپتاحسگرها)
Abstract
حسگرها و آپتاحسگرهای الکتروشیمیایی اجـزا، عملکـرد و کاربـرد (مروری بر جدیدترین فناوری¬های ساخت حسگرها و آپتاحسگرها)
شیمی ترکیبات گیاهی
چکیده
شیمی ترکیبات گیاهی
Metal-organic frameworks-derived Zn-Ni-P nanostructures as high performance electrode materials for electrochemical sensing
Abstract
Metal-organic frameworks-derived Zn-Ni-P nanostructures as high performance electrode materials for electrochemical sensing
The fabrication of hierarchical nanostructure based on metal–organic frameworks (MOFs)-derived transition-metal phosphides (TMPs) has become a hot topic in electrochemical sensor application owing to its unique properties. Herein, a scalable and facile strategy was proposed to prepare MOF-derived bimetallic Zn-Ni-P nanostructures. The material characterization showed that MOFs-derived Zn-Ni-P has flower-like structure that built from small 2D nanosheets. The MOFs-derived Zn-Ni-P was prepared via a facile phosphorization of Zn-Ni-MOF precursor in N2 atmosphere. This MOF-derived TMPs electrode materials offer excellent electrocatalytic activity toward isoprenaline (IPN) oxidation. In addition, the electrode shows wide two linear range (0.2 µM −5 mM and 5 mM-14 mM), short response time (<1s), low detection limit (0.06 µM), good sensitivity (66.748 μA mM−1), desirable repeatability and reproducibility (RSD < 3.5%), and capability for measuring IPN in real sample, which are comparable or better than most reported works for measuring IPN. This improvement can be due to the synergistic effects of multiple catalytic centers, high surface area, facilitated mass, and electron transfer.
A new method for electrochemical determination of Hippuric acid based on molecularly imprinted copolymer
Abstract
A new method for electrochemical determination of Hippuric acid based on molecularly imprinted copolymer
This study introduces easy detection of Hippuric Acid (HA) through electrochemical polymerization technique. The molecularly imprinted polymer (MIP) was immobilized on a glassy carbon electrode (GCE) through electropolymerization of monomers, including m-dihydroxy benzene (m-DB) and o-aminophenol (o-AP), in presence of HA as the template. Moreover, it was subsequently delineated using electrochemical probe of hexacyanoferrate redox, atomic force microscopy (AFM), fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and electrochemical techniques such as cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). This sensor exhibited limit of detection (0.012 nM) with a good linear range of 0.05–40 nM and 40–500 nM. The developed sensor was properly employed to determine HA in real samples with acceptable results.
Novel Electrochemical Sensor Based on Electropolymerized Dopamine Molecularly Imprinted Polymer for Selective Detection of Pantoprazole
Abstract
Novel Electrochemical Sensor Based on Electropolymerized Dopamine Molecularly Imprinted Polymer for Selective Detection of Pantoprazole
Abstract—In this study, a novel electrochemical sensor through electropolymerization of dopamine (DA) on the surface of the glassy carbon electrode (GCE) was prepared for the determination of Pantoprazole (PAN). Afterwards, it was characterized by scanning electron microscopy (SEM), electrochemical probe of potassium hexacyanoferrate, and electrochemical methods, i.e., differential pulse voltammetry (DPV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The created sensor showed acceptable reproducibility and repeatability, and has a prominent sensitivity and selectivity. It has an acceptable linear range of 0.005 to 1.2 µM, and its limit of detection is 1.3 nM. Finally, the proposed sensor is used to detect PAN in samples of blood serum.
Label-free electrochemical aptasensor for rapid detection of SARS-CoV-2 spike glycoprotein based on the composite of Cu(OH)2 nanorods arrays as a high-performance surface substrate
Abstract
Label-free electrochemical aptasensor for rapid detection of SARS-CoV-2 spike glycoprotein based on the composite of Cu(OH)2 nanorods arrays as a high-performance surface substrate
The development of advanced electrode materials and the combination of aptamer with them have improved dramatically the performance of aptasensors. Herein, a new architecture based on copper hydroxide nanorods (Cu(OH)2 NRs) are directly grown on the surface of screen printed carbon electrode (SPCE) using a two-step in situ, very simple and fast strategy and was used as a high-performance substrate for immobilization of aptamer strings, as well as an electrochemical probe to development a label-free electrochemical aptasensor for SARSCoV-2 spike glycoprotein measurement. The Cu(OH)2 NRs was characterized using X-ray Diffraction (XRD) and electron microscopy (FESEM). In the presence of SARS-CoV-2 spike glycoprotein, a decrease in Cu(OH)2 NRsassociated peak current was observed that can be owing to the target-aptamer complexes formation and thus blocking the electron transfer of Cu(OH)2 NRs on the surface of electrode. This strategy exhibited wide dynamic range in of 0.1 fg mL− 1 to 1.2 µg mL− 1 and with a high sensitivity of 1974.43 μA mM− 1 cm− 2 and low detection limit of 0.03 ± 0.01 fg mL− 1 of SARS-CoV-2 spike glycoprotein deprived of any cross-reactivity in the presence of possible interference species. In addition, the good reproducibility, repeatability, high stability and excellent feasibility in real samples of saliva and viral transport medium (VTM) were found from the provided aptasensor. Also, the aptasensor efficiency was evaluated by real samples of sick and healthy individuals and compared with the standard polymerase chain reaction (PCR) method and acceptable results were observed.
Three-dimensional modeling of streptomycin binding single-stranded DNA for aptamer-based biosensors, a molecular dynamics simulation approach
Abstract
Three-dimensional modeling of streptomycin binding single-stranded DNA for aptamer-based biosensors, a molecular dynamics simulation approach
Streptomycin (STR) an aminoglycoside antibiotic which is used against bacteria in human and animal infection, have serious side effects on different parts of human body. Therefore, there is a crucial need to detect trace amount of it in serum and food products. Aptamers are oligonucleotides or peptides, which bind their targets with high affinity and specificity. These properties make aptamers as suitable candidates for biosensing applications. A 79-mer ss-DNA aptamer was applied for the detection of small amount of STR in various aptasensors. But there is no structural information on the STR-binding aptamer and molecular details underlying the aptamer-STR binding remain unexplored. In this study we provided a 3D-structural model for 79-mer ss-DNA aptamer from the sequence. Using docking program and molecular dynamics (MD) simulation we predicted the binding pocket of ss-DNA aptamer. Our results show STR streptose ring is buried within the groove of DNA model and capped by non Watson-Crick bases. STR interacts with aptamer through forming stable hydrogen bonds. Our computational findings are in fair agreement with experimental results. With the atomic structural details, we gained new insight into the Apt-STR binding interaction that can help to further optimize aptamer efficiency in biosensing applications.
Electronic tongue as innovative instrument for detection of crocin concentration in saffron (Crocus sativus L.)
Abstract
Electronic tongue as innovative instrument for detection of crocin concentration in saffron (Crocus sativus L.)
Electronic tongue is a new approach for simple and fast detection, classification, and quantification of the solved compounds. Crocin is the main source of color of saffron (Crocus sativus L.). An electronic tongue system was used to predict the concentration of saffron crocin in the present study. The measurement system included an electrochemical sensor array based on voltammetry electrodes, a three-electrode cell, a potentiostat, a personal computer. Aqueous analyte were provided by blending pure crocin and different saffron samples from Iran and Spain with distilled water. Output signals of the electronic tongue system were analyzed by principal component analysis and artificial neural networks. Based on principal component analysis, the total variance among pure crocin was 99% and that of saffron samples was 100%. The accuracy of artificial neural network model was 98.80%. The results indicated that the developed electronic tongue system and artificial neural network model can successfully predict crocin concentration in saffron.
Gold nanostructures integrated on hollow carbon N-doped nanocapsules as a novel high-performance aptasensing platform for Helicobacter pylori detection
Abstract
Gold nanostructures integrated on hollow carbon N-doped nanocapsules as a novel high-performance aptasensing platform for Helicobacter pylori detection
Nowadays, there is a lot of interest in the design of advanced nanomaterials in the field of electrochemical aptasensors, which can improve analytical performance. In this work, we have established a synthesis of gold nanostructures supported on hollow carbon N-doped nanocapsules (Au@HNC) for the first time. The TEM, Raman, TGA, FE-SEM, XRD, FT-IR, BET, and EDS mapping were used to morphologically study and characterize the as-prepared Au@HNC nanocapsules. The Au@HNC nanocapsules were used for the ultra-sensitive and fast detection of Helicobacter pylori taking the virtues of good biocompatibility, high electronic conductivity, and large specific surface area. We designed this platform because one of the most well-known problems in the world is Helicobacter pylori infection which causes dangerous stomach diseases. The linearity and detection limit of the Aptamer/Au@HNC aptasensor were found to be 33 CFU mL-1 and 102 to107 CFU mL-1 for Helicobacter pylori, respectively.
Amorphous Ni(OH)2 nano-boxes as a high performance substrate for aptasensor application
Abstract
Amorphous Ni(OH)2 nano-boxes as a high performance substrate for aptasensor application
Recently, the performance of aptasensors has been significantly improved when combined with new nanomaterials. Herein, the amorphous Ni(OH)2 nano-boxes with intact shell structure were synthesized and, then, were used as an efficient substrate for covalent immobilization of the NH2-functionalized aptamer to develop label-free electrochemical aptasensor for ultrasensitive analysis of trypsin. This multidimensional hollow structure places a large amount of surface area in a small space of electrode surface and, thus, increasing the loading of the aptamer strings which significantly increases the sensitivity of measurement. A good linear relationship was found between logarithmic value of trypsin and Rct from 1 fg mL− 1 to 500 ng mL− 1 with a low detection limit of 0.3 fg mL− 1 . Furthermore, the proposed aptasensor showed good reproducibility, high stability and excellent feasibility in biological samples. This study showed that the Ni(OH)2 nano-boxes nanocomposite have various advanced electrochemical properties making them suitable electrode materials for aptasensor application.
A novel ultrasensitive biosensor based on NiCo-MOF nanostructure and confined to flexible carbon nanofibers with high-surface skeleton to rapidly detect Helicobacter pylori
Abstract
A novel ultrasensitive biosensor based on NiCo-MOF nanostructure and confined to flexible carbon nanofibers with high-surface skeleton to rapidly detect Helicobacter pylori
Herein, we aim at designing and synthesizing a specific and sensitive aptasensor for Helicobacter pylori (H. pylori), using a modified electrode with an electrospun nano-sized bimetallic NiCo-metal-organic frameworks nanostructure (NiCo-MOF@C) as platform. As a result, owning to the hydrogen bonds, large amounts of aptamer strands can be bound to the NiCo-MOF@C. The detection limits of 1 CFU. ml−1 and the linearity of 101–107 CFU. ml−1 were obtained. The results of our study show that the proposed impedimetric aptamer-based biosensor has specificity, low detection limit, extended range of linear detection and stability for H. pylori. This new NiCo-MOF@C will become an excellent aptamer-based sensors (aptasensors) platform to detect various analytes.
A novel electrochemical sensor for the determination of histidine based on a molecularly imprinted copolymer
Abstract
A novel electrochemical sensor for the determination of histidine based on a molecularly imprinted copolymer
The present study aimed to report a novel electrochemical sensor through electropolymerization of o-aminophenol (o-AP) and m-dihydroxy benzene (m-DB) as monomers on the surface of the glassy carbon electrode (GCE) for the determination of histidine (His) as a template molecule. The developed sensor exhibited satisfactory sensitivity and high selectivity, and also offered a linear range between 0.005 and 10.0 μM with a detection limit of 0.9 nM. Finally, it is worth mentioning that we also aimed at employing the proposed sensor for the detection of His in blood serum samples.
Selective detection of Asulam with in-situ dopamine electropolymerization based electrochemical MIP sensor
Abstract
Selective detection of Asulam with in-situ dopamine electropolymerization based electrochemical MIP sensor
In this work, a new method is presented based on in-situ electropolymerization of dopamine (DA) monomer and asulam (ASL) as a target molecule to fabricate a molecularly imprinted polymer (MIP) on a glassy carbon electrode (GCE). In this regard, the most basic feature of the prepared sensor is that after template extraction the target molecule, cavities with the same size and stereochemical properties of it, remain on the imprinted polymer matrix. Accordingly, the developed sensing platform showed high selectivity and great sensitivity in ASL detection. The proposed method showed good linear range area from 0.5 to 20 pM with limit of detection of 0.17 pM. The influences of electropolymerization conditions e.g. incubation time, monomer to template concentration, cycle numbers and template extraction time were studied. Finally, it was applied for ASL detection in real samples, and the results were consistent with high-performance liquid chromatography obtained results.
Hierarchical nickel hydroxide nanosheets grown on hollow nitrogen doped carbon nanoboxes as a high-performance surface substrate for alpha-fetoprotein cancer biomarkers electrochemical aptasensing
Abstract
Hierarchical nickel hydroxide nanosheets grown on hollow nitrogen doped carbon nanoboxes as a high-performance surface substrate for alpha-fetoprotein cancer biomarkers electrochemical aptasensing
During recent decades, we have witnessed a great improvement in the performance of aptamer-based sensors, specifically when aptamers are combined with new nanomaterials; as a platform for biosensors. The design of hollow carbon-based materials has also received a lot of attention due to its excellent properties in various applications. Herein, we aim at designing hierarchical porous Ni(OH)2 nanosheets on hollow N-doped carbon nanoboxes Ni(OH)2@N-C n-box). In this sense, we obtained the hollow N-C n-box skeletons from the Fe2O3 nanocubes template. The development of label-free electrochemical aptasensor was carried out using the covalently immobilizing NH2-functionalized aptamer on Ni(OH)2@N-C n-box as an efficient substrate. The Ni(OH)2@N-C n-box was characterized using scanning fourier transform infrared spectroscopy (FTIR), X-ray Diffraction (XRD), Brunauer, Emmett and Teller (BET), transmission electron microscopes (TEM) and electron microscopy (FESEM). The electrochemical evaluations clarified the fact that a linear relationship exists between the alpha-fetoprotein (AFP) contents and the charge transfer resistance (Rct) (from 1 fg mL−1 to 100 ng mL−1) with a low detection limit of 0.3 fg mL−1. Moreover, regarding the aptasensor, the superior detection recoveries were experienced in real biological samples, illustrating its great detection performance and practical feasibility. Considering the aptasensor application, these studies showed that Ni(OH)2@N-C n-box possesses different enhanced electrochemical features, making it appropriate as an electrode material for aptasensor application.
Two-Dimensional Mesoporous Copper Hydroxide Nanosheets Shelled on Hollow Nitrogen-Doped Carbon Nanoboxes as a High Performance Aptasensing Platform
Abstract
Two-Dimensional Mesoporous Copper Hydroxide Nanosheets Shelled on Hollow Nitrogen-Doped Carbon Nanoboxes as a High Performance Aptasensing Platform
The design of metal hydroxide nanosheets on hollow carbonaceous nanostructures has attracted immense attention because of their unparalleled physical/chemical properties with sizeable intrinsic capability to load specific chemicals. Herein, a novel metal hydroxide based on hollow nitrogen-doped carbon nanoboxes shelled with a nanoporous copper hydroxide nanosheet (Cu(OH)2@N−C n-box) was fabricated. The structure of fabricated hollow nanomaterials was fully characterized by various physicochemical characterization techniques such as field emission scanning electron microscopy (FESEM), high-resolu1tion transmission electron microscopy (HRTEM), Brunauer−Emmett−Teller (BET) method, thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), and Fouriertransform infrared (FTIR) and Raman spectroscopies, which confirmed that a complex core−shell structure with ordered two-dimensional Cu(OH)2 nanostructures on N−C n-box was successfully prepared. The Cu(OH)2@ N−C n-box is used to fabricate an advanced electrochemical aptasensor to measure the protein enzyme trypsin. In addition, it acts as an excellent substrate with abundant functional groups and a large surface area for fixing and bonding aptamers on the modified glass-carbon surface. Each step of electrode surface modification was investigated through ferro/ferri cyanide probe signal changes. The designed aptasensor can determine trypsin in a linear concentration between 10 to 80 pg/mL and 10 to 80 ng/mL with a detection limit of 3 pg/mL. The proposed system also has a desirable selectivity in the presence of different interferences. This is the first report on the rational design of hollow carbonaceous materials hybridized Cu(OH)2 for the electrochemical application
An electrochemical immunosensor using SARS-CoV-2 spike protein-nickel hydroxide nanoparticles bio-conjugate modified SPCE for ultrasensitive detection of SARS-CoV-2 antibodies
Abstract
An electrochemical immunosensor using SARS-CoV-2 spike protein-nickel hydroxide nanoparticles bio-conjugate modified SPCE for ultrasensitive detection of SARS-CoV-2 antibodies
As a promising approach for serological tests, the present study aimed at designing a robust electrochemical biosensor for selective and quantitative analysis of SARS-CoV-2-specific viral antibodies. In our proposed strategy, recombinant SARS-CoV-2 spike protein antigen (spike protein) was used as a specific receptor to detect SARS-CoV-2-specific viral antibodies. In this sense, with a layer of nickel hydroxide nanoparticles (Ni(OH)2 NPs), the screen-printed carbon electrode (SPCE) surface was directly electrodeposited to ensure better loading of spike protein on the surface of SPCE. The differential pulse voltammetry (DPV) showed signals which were inversely proportional to the concentrations of the antibody (from 1 fg mL− 1 L to 1 µg mL− 1 ) via a specific and stable binding reaction. The assay was performed in 20 min with a low detection limit of 0.3 fg mL− 1 . This biodevice had high sensitivity and specificity as compared to non-specific antibodies. Moreover, it can be regarded as a highly sensitive immunological diagnostic method for SARS-CoV-2 antibody in which no labeling is required. The fabricated hand-held biodevice showed an average satisfactory recovery rate of ~99-103% for the determination of antibodies in real blood serum samples with the possibility of being widely used in individual serological qualitative monitoring. Also, the biodevice was tested using real patients and healthy people samples, where the results are already confirmed using the enzyme-linked immunosorbent assay (ELISA) procedure, and showed satisfactory results.
Electrochemical Detection of Celestine Blue Based on Screen Printed Carbon Electrode Modified with Molecular Imprinted Polymer and NiO Nanoparticles
Abstract
Electrochemical Detection of Celestine Blue Based on Screen Printed Carbon Electrode Modified with Molecular Imprinted Polymer and NiO Nanoparticles
A simple and rapid electrochemical method was developed for the detection of trace amount of Celestine blue (CB) at the surface of modified screen-printed carbon electrode (SPCE) with nickel oxide (NiO) nanoparticles and molecular imprinted polymer (MIP). Various types of electrochemical methods; containing, differential pulse voltammetry (DPV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in order to probe the characteristics of the sensor toward CB was employed. The selectivity, real sample analysis (efficiency), the linear concentration range, and the detection limit of CB at the MIP/NiO-NPs/SPCE were evaluated by DPV method. FT-IR spectroscopy was applied in order to characterize the synthesized CB-MIP and non-molecular imprinted polymers (NIP). Scanning electron microscopy (SEM) and BET (Brunauer-Emmett-Teller) techniques were used for surface morphology and porosity properties of CB-MIP and NIP. A linear range was presented by the sensor for CB concentration between 2-150 µM with detection limit (S/N=3) of 0.35 µM. The sensor is able to selectively detect the CB molecules over the potential interferences. The sensor was used to determine CB in the real sample with acceptable results.
Metal–organic framework-derived CoNi-P nanoparticles confined into flexible carbon nanofibers skeleton as high-performance oxygen reduction reaction catalysts
Abstract
Metal–organic framework-derived CoNi-P nanoparticles confined into flexible carbon nanofibers skeleton as high-performance oxygen reduction reaction catalysts
The rational design of high performance oxygen reduction reaction (ORR) catalysts based on metal chalcogenides derived carbon materials with stable porous structure and rapid electron/mass transport properties is highly desirable yet a great challenge to date. Herein, we synthesize and design metal–organic framework-derived CoNiP nanoparticles confined into a flexible carbon nanofiber skeleton (C@CoNi-P@C) as ORR catalysts with excellent activity. Using electrospinning of nano size bimetallic NiCo-MOF particles, followed by a precisely controlled annealing process at PH3 atmosphere, composite C@CoNi-P@C catalysts with uniform fiber morphology can be obtained. By comparing the catalytic performance with pure CNF, it is found that the C@CoNi-P@C mixture can be better for the ORR catalyst. With these favorable features, C@CoNi-P@C exhibits an overall distinguished ORR performance in alkaline media, which has a high onset potential of 0.83 V (vs. RHE), half-wave potential of 0.73 V (vs. RHE) and electron transfer number (4). This work introduces a new concept for design of new electrocatalysts using the electrospinning technique for energy storage and conversion application.
Rationally designed of hollow nitrogen doped carbon nanotubes double shelled with hierarchical nickel hydroxide nanosheet as a high performance surface substrate for cortisol aptasensing
Abstract
Rationally designed of hollow nitrogen doped carbon nanotubes double shelled with hierarchical nickel hydroxide nanosheet as a high performance surface substrate for cortisol aptasensing
The development of advanced electrode materials based on hollow metal hydroxide nanosheets/carbonaceous nanostructures that have unique chemical/physical properties and sizeable inherent cavity to load specific chemical, has attracted immense attention. Herein, novel metal hydroxide nanosheets/carbonaceous nanostructures based on hollow mesoporous Ni(OH)2 nanosheet double shelled on hollow nitrogen doped carbon nanotubes (Ni(OH)2@N–C n-Tube) were designed. The N–C n-Tube skeleton was derived from its corresponded Fe2O3 nanorod with a simple self-polymerizing method, followed by an annealing and etching method. This advanced core-double shell array with ordered hierarchical Ni(OH)2 nano-architectures was successfully used as a high performance surface substrate for cortisol (COR) aptasensing. The Ni(OH)2@N–C n-Tube shows unique characteristics including high surface area with rich functional group for bonding and fixing aptamer when used as a surface substrate. This proposed aptasensor can detect COR in a linear concentration between 1 pM to 80 pM and 0.1 nM to 25 nM with a detection limit of 0.3 pM and good selectivity in the presence of various interferences
Rapid and sensitive determination of Pseudomonas aeruginosa by using a glassy carbon electrode modified with gold nanoparticles and aptamer-imprinted polydopamine
Abstract
Rapid and sensitive determination of Pseudomonas aeruginosa by using a glassy carbon electrode modified with gold nanoparticles and aptamer-imprinted polydopamine
seudomonas aeruginosa causes a long-term chronic disease that low concentrations of Pseudomonas aeruginosa can cause infection; therefore, rapid detection of this Pseudomonas aeruginosa is very important. This study presents a method with a combination of molecular imprinting and aptasensing in order to measure Pseudomonas aeruginosa (P. aeruginosa). The double exact molecular recognition property of the molecular imprinting polymers and aptamers led to superb sensing properties. In this study, gold nanoparticles were used as specific intermediate and interface in order to increase the aptamer sequence loading rate. The capability of this method was investigated by several electrochemical techniques. The sensor renders a wide linear dynamic concentration range of 101 to107 CFU·ml−1 with low detection limit of 1 CFU·ml−1. In addition, satisfactory results were found in determining P. aeruginosa using blood samples. This sensor has many advantages, such as low cost, high stability, low response time, and high sensitivity for P. aeruginosa measurement.
Aptamer-based electrochemical detection of Tyrosinamide using metal-organic frameworks/silver nanoparticles modified glassy carbon electrode
Abstract
Aptamer-based electrochemical detection of Tyrosinamide using metal-organic frameworks/silver nanoparticles modified glassy carbon electrode
In this report, a new aptamer-based assay was presented reporting the electrochemical aptasensing for sensing tyrosinamide (Tyr-NH2). This strategy was relied on unbeatable conformational flexibility and specific recognition of aptamers. The tyrosinamide aptamer (Tyr-NH2-aptamer) was immobilized onto the metal-organic frameworks/silver nanoparticles modified glassy carbon electrode and hexacyanoferrate was selected as a probe to monitor interface variations during modification of the electrode and the aptamer conformational change generated by the Tyr-NH2 binding. Results showed that measurements by using electrochemical impedance spectroscopy had linear with the Tyr-NH2 concentrations in range of 0.01-0.25 nM and 0.25-1.15 nM. Detection limit of this system was found to be 2.3 pM. This method was also used to the Tyr-NH2 detection in serum samples successfully. Remarkable simplicity, ease of use and low-cost, make methodology as sensitive analytical system for sensing of the Tyr-NH2 that can be miniaturized. This strategy offers some promising advantages in reliable detection of the Tyr-NH2, which may be helpful in the routine analysis.
Flexible NiP2@hollow N-doped nanocapsules/carbon nanofiber as a freestanding electrode for glucose sensing
Abstract
Flexible NiP2@hollow N-doped nanocapsules/carbon nanofiber as a freestanding electrode for glucose sensing
The development of flexible and binder free electrocatalytic materials based on low cost metal dichalcogenide and low weight carbon nanofibers (CNF) has been materialized as an effective strategy for the fabrication of advanced super light portable, wearable, and stretchable sensor devices. In this work, the NiP2/hollow N-doped nanocapsules decorated nitrogen-doped carbon nanofiber (NiP2/CNCNF), have been designed for the first time. The NiP2/CNCNF was used directly as a flexible and freestanding electrode toward electrocatalytic and nonoenzymatic glucose sensing. The NiP2/CNCNF displayed high conductivity, flexibility with low weight, excellent electrochemical activity, steadiness and enhanced electron transfer rate.
Electrochemical immunosensor with Cu2O nanocube coating for detection of SARS-CoV-2 spike protein
Abstract
Electrochemical immunosensor with Cu2O nanocube coating for detection of SARS-CoV-2 spike protein
Severe acute respiratory syndrome SARS-CoV-2 has caused a global pandemic starting in 2020. Accordingly, testing is crucial for mitigating the economic and public health effects. In order to facilitate point-of-care diagnosis, this study aims at presenting a label-free electrochemical biosensor as a powerful nanobiodevice for SARS-CoV-2 spike protein detection. Utilizing the IgG anti-SARS-CoV-2 spike antibody onto the electrode surface as a specific platform in an ordered orientation through staphylococcal protein A (ProtA) is highly significant in fabricating the designed nanobiodevice. In this sense, the screen-printed carbon electrode modified with Cu2O nanocubes (Cu2O NCs), which provide a large surface area in a very small space, was applied in order to increase the ProtA loading on the electrode surface. Accordingly, the sensitivity and stability of the sensing platform significantly increased. The electrochemical evaluations proved that there is a very good linear relationship between the charge transfer resistance (Rct) and spike protein contents via a specific binding reaction in the range 0.25 fg mL−1 to 1 μg mL−1 . Moreover, the assay when tested with influenza viruses 1 and 2 was performed in 20 min with a low detection limit of 0.04 fg mL−1 for spike protein without any cross-reactivity. The designed nanobiodevice exhibited an average satisfactory recovery rate of ~ 97–103% in different artificial sample matrices, i.e., saliva, artificial nasal, and universal transport medium (UTM), illustrating its high detection performance and practicability. The nanobiodevice was also tested using real patients and healthy samples, where the results had been already obtained using the standard polymerase chain reaction (PCR) procedure, and showed satisfactory results.
Hollow carbon nanocapsules-based nitrogen-doped carbon nanofibers with rosary-like structure as a high surface substrate for impedimetric detection of Pseudomonas aeruginosa
Abstract
Hollow carbon nanocapsules-based nitrogen-doped carbon nanofibers with rosary-like structure as a high surface substrate for impedimetric detection of Pseudomonas aeruginosa
The design of hollow mesoporous carbon-based materials has attracted tremendous attention, due to their sizeable intrinsic cavity to load specific chemical and unique physical/chemical properties in various applications. Herein, we have established an effective strategy for the preparation of novel hollow carbon nanocapsulesbased nitrogen-doped carbon nanofibers (CNCNF) with rosary-like structure. By embedding ultrafine hollow carbon nanocapsules into electrospun polyacrylonitrile (PAN) skeleton, the as-designed composite CNFs were carbonized into hierarchical porous CNFs, consisted of interconnected nitrogen-doped hollow carbon nanocapsules. Due to its individual structural properties and unique chemical composition, the performance of CNCNF was evaluated in aptasensor application via the detection of Pseudomonas aeruginosa (PA). Under optimized conditions, the aptasensor based on CNCNF has a detection limit of 1 CFU⋅mL− 1 and a linear range from 101 CFU ⋅mL− 1 to 107 CFU ⋅mL− 1 (n = 3). Moreover, the designed aptasensor possesses high sensivity, high selectivity, low detection limit, and high reproducibility. These studies showed that the CNCNF material offers a wide variety of enhanced electrochemical features as an electrode material for aptasensor application.
Fabrication of an electrochemical biodevice for ractopamine detection under a strategy of a double recognition of the aptamer/molecular imprinting polymer
Abstract
Fabrication of an electrochemical biodevice for ractopamine detection under a strategy of a double recognition of the aptamer/molecular imprinting polymer
The importance of RAC tracking in human biofluids has boosted many demands for designing an ultrasensitive tool to determine the trace value of the RAC from clinical, judicial, and forensic centers. In this study, an electrochemical biodevice has developed for the highly selective detection of this illegal feed additive under a double recognition strategy of the aptamer (Apt) and molecular imprinting polymer (MIP) on a glassy carbon electrode (GCE). The sensing relies on this fact that both the MIP and Apt act synergistically to trap the RAC molecules. The sensing surface fabrication steps have been monitored by some electrochemical techniques such as electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV(. The charge transfer resistance (Rct) value of the redox probe as a representative of the biodevice response has increased linearly with the RAC concentration increasing in a dynamic range of 1 fM to 1.90 mM. The detection limit (LOD) value has been estimated to be 330 aM, lower than all of the reported methods in the RAC sensing. Furthermore, the practical feasibility of biodevice has been evaluated in some human blood serum and urine samples. This strategy offers some useful advantages in reliable detection of the RAC, which may help in the routine analysis, as mandated by regulatory agencies.
Applications of electronic tongue system for quantifcation of safranal concentration in safron (Crocus sativus L.)
Abstract
Applications of electronic tongue system for quantifcation of safranal concentration in safron (Crocus sativus L.)
In the present research the electronic tongue system was proposed consisted of an array of 4 voltammetric sensors to discriminate saffron samples based on the safranal concentration. Different samples were provided by blending saffron samples with distilled water and pure safranal with ethanol. The provided signals by the electronic tongue system were analyzed using the PCA and ANN methods. The total variance among safranal concentrations by PCA method were 90% and 100% in pure safranal and saffron samples, respectively. Also, it was revealed that the electronic tongue could provide good prediction for safranal concentration in saffron as 98.81% accuracy by means of optimized ANN model. Results showed that there are some relationships between HPLC and electronic tongue signals to determine safranal concentration levels in different saffron samples.
Three-dimensional NiCo2O4 nanowires encapsulated in nitrogen-doped carbon networks as a high-performance aptamer stabilizer for impedimetric ultrasensitive detection of hepatitis C virus core antigen
Abstract
Three-dimensional NiCo2O4 nanowires encapsulated in nitrogen-doped carbon networks as a high-performance aptamer stabilizer for impedimetric ultrasensitive detection of hepatitis C virus core antigen
Recently, the performance of aptamer-based sensors has been greatly improved by the combination of aptamers with novel nanomaterials. Herein, the hierarchical porous 3D-NiCo2O4 nanowires, shelled with a thin layer of Ndoped carbon (l) with sea-urchin-like morphology, were successfully prepared by a facile protocol. The 3D NC@NiCo2O4 NWs combine the electrochemical advantages of Ni and Co species by exhibiting higher specific capacitance and active sites and also much higher conductivity. More significantly, the carbon layer improves the stability, conductivity and porosity of the nanowires. Benefiting from such a hierarchical structure, 3D NC@NiCo2O4 NWs fit a large amount of surface area in a very small space. Therefore, the 3D N-C@NiCo2O4 NWs was applied in order to increase the hepatitis C virus core antigen (HCV) aptamer load on the electrode that significantly increased the sensitivity of the sensor. The electrochemical evaluations were proved that there exists a very good linear relationship between the charge transfer resistance (Rct) and HCV contents in the range of 0.5 fg mL− 1 to 0.12 pg mL− 1 with a low detection limit of 0.16 fg mL− 1 . Besides, it was in real biological samples that the aptasensor experienced superior detection recoveries which illustrated its high detection performance and feasibility for practicability.
Sensitive amperometric detection of hydrazine using a rutin/ graphene-chitosan nanocomposite modified glassy carbon electrode
Abstract
Sensitive amperometric detection of hydrazine using a rutin/ graphene-chitosan nanocomposite modified glassy carbon electrode
The present study describes a new approach for the investigation of electrocatalytic oxidation of hydrazine by using a glassy carbon electrode (GCE) modified by graphene chitosan nanocomposite (Gr-Cs) and Rutin (Ru). The heterogeneous electron transfer rate constant (ks) and the surface coverage of immobilized Ru on the Gr‒Cs/GCE were obtained as 63 s−1 and 4.48×10−11 mole cm−2, respectively. The designed sensor showed excellent electrocatalytic activity toward oxidation of hydrazine. The catalytic rate constant (kcat) of the modified electrode toward N2H4 is 6.3 ×103 M-1s-1. Linear relationship between amperometric current response and hydrazine concentration was observed in the range of 0.3-1500 µM and the limit of detection was 90 nM (S/N=3). In addition, the modified electrode has an excellent anti-interference property in the presence of other potentially interfering species as well as a good operational stability. To evaluate the applicability of the proposed sensor, it was employed to determine hydrazine in a drinking water sample
Electrochemical immunosensor for determination of Staphylococcus aureus bacteria by IgY immobilized on glassy carbon electrode with electrodeposited gold nanoparticles
Abstract
Electrochemical immunosensor for determination of Staphylococcus aureus bacteria by IgY immobilized on glassy carbon electrode with electrodeposited gold nanoparticles
A new ultrasensitive immunosensor is proposed based on the covalently attached anti-protein A antibody (IgY) on deposited gold nanoparticle (AuNP)-modified glassy carbon electrode (GCE) for the electrochemical measurement of Staphylococcus aureus (S. aureus). Chicken IgY as a capture antibody provides highly selective and specific binding to the target bacteria and selectively captures the S. aureus in its three-dimensional space. Due to that it can eliminate the interference from protein G-producing Streptococcus. In addition, the electron-transfer characteristic of [Fe(CN)6] 4−/3− is hindered by this combination; as it is reflected on the electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) curves. The proposed immunosensor displays a wide linear dynamic range from 10 to 107 CFU mL−1 with a detection limit of 3.3 CFU mL−1 with RSD 3.0%. It is capable to accurately determine S. aureus in milk and human blood serum as a complex matrix sample with satisfactory recovery of ∼ 97–103%. The immunosensor also displays high selectivity over other bacteria and acceptable stability. Presumably, our study can be regarded as the first one to report chicken IgY in order to detect S. aureus based on an electrochemical method.
Cu-In-S/ZnS quantum dots/silver nanoparticles nanocomposites-modified electrode as an electrochemical label-free aptasensor for the detection of β-casomorphin 7 in early distinguish of autism
Abstract
Cu-In-S/ZnS quantum dots/silver nanoparticles nanocomposites-modified electrode as an electrochemical label-free aptasensor for the detection of β-casomorphin 7 in early distinguish of autism
In this study, the efficiency of a nanocomposite contains the quantum dots and silver nanoparticle (AgNP/QDs) has been investigated to modify a glassy carbon electrode (GCE) in the aptasensor construction. Accordingly, the modified GCE provides a sub-layer to load more aptamers (Apts) through a linker agent of the AgNP to identify the β-casomorphin 7 (BCM-7) as an autism biomarker. The Apt/target interaction on the sensing interface surface leads to an electron transfer hindrance of the Rutin (RU) as a green redox probe. Consequently, a corresponding decrease in the current signal of the RU is achieved. The electrochemical studies show that the obtained signal responses linearly correlate with various BCM-7 concentrations in two ranges of 1 pM-20 nM and 20 nM-1.3 µM with a calculated limit of detection (LOD) 332 fM. The label-free aptasensor presents a high selectivity towards the BCM-7 in the presence of several similar amino acids. The analysis of the human urine and blood samples demonstrates the sufficient capability of the aptasensor in the BCM-7 detection in the real samples.
Facile synthesis of a covalent organic framework (COF) based on the reaction of melamine and trimesic acid incorporated electrospun nanofiber and its application as an electrochemical tyrosinamide aptasensor
Abstract
Facile synthesis of a covalent organic framework (COF) based on the reaction of melamine and trimesic acid incorporated electrospun nanofiber and its application as an electrochemical tyrosinamide aptasensor
In this research, for the first time, a high-performance electrochemical aptasensor assay based on electrospun covalent organic framework (COF) nitrogen-doped carbon nanofiber (COFCNF) was designed and dedicated to tyrosinamide sensing. The COF is prepared via a condensation reaction between trimesic acid and melamine. The COFCNF has been used to modify the electrode surface in an electrochemical sensor based on the aptamer because the COFCNF increases electrochemical activity. The as-prepared nanofibers were characterized by Brunauer Emmett Teller analysis, Field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. Electrochemical impedance spectroscopy and cyclic voltammetry were used for the fabrication and assessment of the proposed aptasensor in Fe(CN)64−/3− as a redox probe. The proposed aptasensor for tyrosinamide has a detection limit of 0.53 pM and linearity from 0.0016 to 0.08 nM and 0.08–9 nM.
Hierarchical hollow sea-urchin-like Ni–Co diselenide encapsulated in N-doped carbon networks as an advanced core-shell bifunctional electrocatalyst for fabrication of nonenzymatic glucose and hydrogen peroxide sensors
Abstract
Hierarchical hollow sea-urchin-like Ni–Co diselenide encapsulated in N-doped carbon networks as an advanced core-shell bifunctional electrocatalyst for fabrication of nonenzymatic glucose and hydrogen peroxide sensors
The design of bimetallic selenide configurations has been regarded as a feasible strategy to modulate the electronic structure of the electrocatalysts for sensors application. In this sense, unique hierarchical porous threedimensional Ni–Co diselenide nanowires (3D Co0.6Ni0.4Se2 NWs) coated with N-doped carbon thin layer (3D N-C@Co0.6Ni0.4Se2 NWs) with hollow sea-urchin-like overall morphology were fabricated and used as an effectual bifunctional electrocatalyst for glucose oxidation and hydrogen peroxide reduction. Regarding the advantages of this porous and 3D structure, the N-C@Co0.6Ni0.4Se2 NWs offer abundant electrochemical-active sites, high availability to the electrolyte/analyte, and high conductivity due to the synergistic effect of bimetals, coated N-doped carbon and selenide. As an amperometric glucose sensor, it shows a high sensitivity of 1439 and 239 μA mM− 1 cm− 2 and wide linear range from 0.5 μM to 2.2 mM and 2.2 mM–12.2 mM with a low detection limit of 0.16 μM. Moreover, amperometric H2O2 sensing will be recognized with a sensitivity of 89 and 31.8 μA mM− 1 cm− 2 , a linear range from 0.5 μM to 6 mM and 6 mM–15 mM, and a detection limit of 0.16 μM (S/N = 3). Moreover, the developed sensor shows a great potential in determining glucose and H2O2 in biological real samples.
Design of an electrochemical aptasensor based on porous nickel‑cobalt phosphide nanodiscs for the impedimetric determination of ractopamine
Abstract
Design of an electrochemical aptasensor based on porous nickel‑cobalt phosphide nanodiscs for the impedimetric determination of ractopamine
A trend in the development of aptasensors is introducing high-performance nanomaterials as a platform of biosensors with suitable aptamer binding capacity and good electrochemical activity. Here, for the first time, we report the application of nickel‑cobalt phosphide nanodiscs (NiCo-P NDs) in the design of an aptasensor for the impedimetric determination of ractopamine (RAC). The highly porous NiCo-P NDs were synthesized by a simple two-step method. Due to the high porosity and large specific surface area of NiCo-P NDs, it increases the loading of the aptamers on the modified electrode and improves the performance of the proposed aptasensor. Under optimal conditions, the designed aptasensor could determine RAC in a wide linear concentration range from 0.50 f. to 1.25 μM and has an ultralow limit of detection (LOD) of 166 aM (S/N = 3). The fabricated electrochemical aptassensor is reproducible, selective, cost-effective, which was successfully used to RAC detection in blood serum samples. We hope that our study will develop the application of the multi-metal phosphide nanodiscs in biosensing devices.
Rational design of hollow core-double shells hybrid nanoboxes and nanopipes composed of hierarchical Cu-Ni-Co selenides anchored on nitrogen‐doped carbon skeletons as efficient and stable bifunctional electrocatalysts for overall water splitting
Abstract
Rational design of hollow core-double shells hybrid nanoboxes and nanopipes composed of hierarchical Cu-Ni-Co selenides anchored on nitrogen‐doped carbon skeletons as efficient and stable bifunctional electrocatalysts for overall water splitting
It is of prime importance to develop efficient nonprecious noble-metal-free water splitting bifunctional electrocatalysts for both H2 and O2 evolution reactions (HER and OER), which remains a grand challenge. However, the design of hollow nanostructured based on di- and tri-metal selenides, particularly non-spherical hollow nanostructures, is scarcely reported. Herein, for the first time, novel tri-metal selenides based on hollow Cu0.4Ni0.3Co0.3Se2 mesoporous nanosheet double shell were successfully designed on hollow N-doped carbon nanoboxes (Cu0.4Ni0.3Co0.3Se2@N-C n-box) and nanopipes (Cu0.4Ni0.3Co0.3Se2@N-C n-pipe). The hollow N-C n-box and N-C n- pipe skeletons were obtained from the related Fe2O3 nanocubes and nanorods templates that have prepared with completely different morphologies via only a minor change in synthesis step. Remarkably, benefiting from the special electronic structure engineering and unique hollow hierarchical design with high surface areas, open channels for effective gas releasing, fast electron/mass transport, the resulting advanced electrocatalysts provide outstanding OER activity as well as desirable HER performance in the alkaline medium. Moreover, an overall water splitting device is assembled using two symmetrical Cu0.4Ni0.3Co0.3Se2@N-C n-box electrodes as anode and cathode, which can deliver a current density of 10 mA cm−2 at a cell voltage as low as 1.53 V. More significantly, in addition to extraordinary operational stability of the electrolyzer, it can achieve high current density of 100 mA cm−2 with only cell voltage of 1.79 V, respectively, which are very useful for practical application. This work offers a rational strategy for the structure engineering of advanced hollow hybrid nanostructures as a nonprecious noble-metal-free water splitting
Determination of BCM-7 based on an ultrasensitive aptasensor fabricated of gold nanoparticles and ZnS quantum dots
Abstract
Determination of BCM-7 based on an ultrasensitive aptasensor fabricated of gold nanoparticles and ZnS quantum dots
In thisstudy, anultrasensitive electrochemical aptasensor for the determination oftheβ-casomorphin 7(BCM-7) as a promising biomarker of autism disorder is introduced. According to the proposed strategy, a glassy carbon electrode (GCE) was modified by thiourea capped-ZnS QDs (ZnS-QDs) and gold nanoparticles (AuNPs) to further immobilization the amino-aptamer (NH2-Apt) on its surface. The NH2-Apt as a receptor of the BCM-7 was attached to the embedded surface via a formation of the Au–N bonds between the AuNPs and amino groups of the Apt. The evaluation of aptasensor by various electrochemical techniques exhibited successful sensing of the BCM-7 under twobroadlinear concentration ranges from1fM to0.6μMwitha limit ofdetection (LOD) down to 350aM. Also, the performance of the aptasensor in BCM-7 detection in real human urine samples was satisfactorily investigated. These findings may facilitate distinguish of this challenging disorder and help human health.
Pd/[C2NH2mim][Br] Thin Film Versus Pd/[C8mim][Cl] or Pd/[C8mim] [BF4]: Catalytic Applications in Electrooxidation of Methanol, p‑Nitrophenol Reduction and C–C Coupling Reaction
Abstract
Pd/[C2NH2mim][Br] Thin Film Versus Pd/[C8mim][Cl] or Pd/[C8mim] [BF4]: Catalytic Applications in Electrooxidation of Methanol, p‑Nitrophenol Reduction and C–C Coupling Reaction
In this study, diferent ionic liquids including 1-aminoethyl-3-methyl-imidazolium bromide [C2NH2mim][Br] (1), 1-methyl3-octylimidazolium chloride [C8mim][Cl] (2) and 1-methyl-3-octylimidazolium tetrafuoroborate [C8mim][BF4] (3) were applied to stabilize Pd nanoparticles (NPs) at toluene/water interface as thin flms. Field emission-scanning electron microscopy (FE-SEM) images showed puckered chains of ionic liquid (1) around the Pd NPs as fower nanostructures. Transmission electron microscopy (TEM) image of Pd/1 showed clearly core–shell nanostructures. Furthermore, applications of Pd/1, Pd/2 and Pd/3 were investigated in the Suzuki–Miyaura C–C coupling reaction in the presence and absence of ultrasonic waves, hydrogenation catalysis of p-nitrophenol reduction and methanol oxidation reaction. Interestingly, Jf (forwarding current density due to methanol oxidation) was observed only for Pd/1. We believe that interactions of –NH2 and imidazolium groups of ionic liquid 1 with Pd particles are very important in producing of puckered shells around the Pd NPs. Injection of electron density from –NH2 group and Br− of ionic liquid 1 to Pd content tends to Pd be softer than other ionic liquids (2 or 3). This efect weakens the strength of Pd–O and facilitates the intermolecular reductive elimination between Pd–O and Pd–C≡O in rate-determining step of methanol oxidation to produce CO2 product. However, electron releasing group accelerates the increasement in negative charge density of metal accelerates intramolecular or intermolecular reduction elimination.
Architecting of a biodevice based on a screen-printed carbon electrode modified with the NiONP nanolayer and aptamer in BCM-7 detection
Abstract
Architecting of a biodevice based on a screen-printed carbon electrode modified with the NiONP nanolayer and aptamer in BCM-7 detection
In this study, an ultrasensitive and robust biodevice implemented on a screen-printed carbon electrode (SPCE) surface is introduced. The β-casomorphin-7 (BCM-7) peptide as an early warning sign of autism disorder is distinguished in this system. The SPCE surface was directly electrodeposited with a nanolayer of the nickel oxide nanoparticles (NiONP). In next step, an Apt sequence as a capture of the BCM-7 was strongly attached on this surface. The embedded sensing interface offered some admirable characterizes to detect the BCM-7. The obtained DPV signals were reversely proportional to the concentrations of the BCM-7 through a stable binding reaction in two working linear ranges from 0.5 × 10−9-1.5 μmol l-. Also, an unrivaled limit of detection (LOD) value of 166.6 aM was achieved that is so superior by other reported methods in the BCM-7 sensing. This hand-held biodevice was satisfactorily tested for the BCM-7 detection in human urine and blood sample with an average recovery rate of ∼101.87 %. More importantly, this strategy is free from labeling steps, complex sample processing and interference from common biomolecules in blood or urine. Due to the inherent advantages of the SPCE and the NiONP, utilizing this facile sensing interface may be an ideal choice in constructing of the ultrasensitive biodevice with low cost for distinguishing of the autism disorder.
Designing of an ultrasensitive BCM-7 aptasensor based on an SPCE modified with AuNR for promising distinguishing of autism disorder
Abstract
Designing of an ultrasensitive BCM-7 aptasensor based on an SPCE modified with AuNR for promising distinguishing of autism disorder
Abstractly, in this study, an aptasensor is introduced based on a platform consisting of the gold nanorod (AuNR) on a screen printed carbon electrode (SPCE) surface. The aptasensor is applied for detection of the β-casomorphin (BCM-7) as a promising biomarker of autism disorder. The NH2-Apt sequence is directly immobilized onto the AuNR/SPCE surface by formation of a chemisorption bond between the amine-Au groups. By incubation of the BCM-7 onto the aptasensor surface, the aptasensor directed against BCM-7 and cleverly formed a target/Apt complex to produce a measurable electrical current change. The aptasensor shows linearity over the range of 1 fmol L−1 to 25 nmol L−1 with a limit of detection (LOD) of 334 amol L−1. Furthermore, the function of the aptasensor in real samples such as human urine and plasma samples is evaluated. The achieved satisfactory results are mainly due to three main reasons including (1) the large specific surface area of the AuNR which forms a 3D network on the SPCE surface to capture more Apt sequences at the sensing interface, (2) utilizing Apt as the BCM-7 receptor with inherent unique properties to produce a synergetic effect with the AuNR, and finally, (3) effective using screen printing technology with the fantastic capability to less cost of the aptasensor preparation. There is hope that miniaturization of the proposed aptasensor may aid future efforts to detect autism symptoms as early as infancy under clinical conditions in real-world.
Development of an Electrochemical Sensor for a Sensitive Determination of Metanil Yellow
Abstract
Development of an Electrochemical Sensor for a Sensitive Determination of Metanil Yellow
In this work, we introduced a sensitive electrochemical sensor in order to accurately detect metanil yellow (MY). Multi-walled carbon nanotube-chitosan (MWCNTs-Chit) nanocomposite was applied to fabricate the sensor on the glassy carbon electrode. The scanning electron microscopy (SEM) was used to investigate the physical morphology of the modified electrode surface. The rate of the electron transfers between MY and electrode can be quickened by the attendance of MWCNTs-Chit nanocomposite due the high surface area, good conductivity as well as excellent catalytic property. Sensitive quantitative detection of the MY was carried out by the monitoring increase of differential pulse voltammetric (DPV) responses of the sensor. The prepared MWCNTs-Chit/GC electrode illustrated a linear response to MY concentration in the range of 1.0 µM to 300.0 µM with a sensitivity and a limit of detection (S/N=3) of 20.0 nAµM-1 and 0.3 µM, respectively. Accordingly, in order to determine MY in real samples with satisfactory results, we applied the proposed sensor.
Electroanalytical sensing of Asulam based on nanocomposite modified glassy carbon electrode
Abstract
Electroanalytical sensing of Asulam based on nanocomposite modified glassy carbon electrode
In this study a facile approach to employ Copper nanoparticle (CuNPs) and multi-walled carbon nanotubes (MWCNT) as the nanomaterial for selective detection of asulam have been investigated. This work reports the electrocatalytic oxidation of asulam on glassy carbon electrodes (GCE) modified with multi-walled carbon nanotubes (MWCNT), ionic liquids (IL), chitosan (Chit) and copper nanoparticles (CuNPs).Using the proposed nanocomposite provides a specific platform with increased surface. The surface morphology of this modified electrode was characterized by field-emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectrometer (EDX) techniques. The electrochemical behaviors of the fabricated sensor were investigated by cyclic voltammetry (CV) and chronoamperometry modes. Under optimal conditions, the amperometric study exhibits two linear ranges of 1–11 and 11–200 μmol L-1 with a detection limit (LOD) of 0.33 nmol L-1 (at an S/N of 3) and sensitivity of 1.9 nA μmol L-1 for Asulam determination. This novel sensor was used to analyze the real sample. The sensor provides a convenient, low-cost and simple method for Asulam detection and proposes new horizons for quantitative detection of Asulam.
AgNPs/QDs@GQDs nanocomposites developed as an ultrasensitive impedimetric aptasensor for ractopamine detection
Abstract
AgNPs/QDs@GQDs nanocomposites developed as an ultrasensitive impedimetric aptasensor for ractopamine detection
Developing easy-to-use and miniaturized sensors for in-field monitoring of targets which is related to human health is necessary. Ractopamine (RAC) is a feed additive with serious side effects that is forbidden in many countries. This study reports the fabrication of an impedimetric aptasensor for ultrasensitive and selective detection of the RAC in human biological fluids. Accordingly, an efficient nanocomposites was synthesized by a beneficial combination of graphene quantum dots (GQDs), quantum dots (QDs) and silver nanoparticles (AgNPs) for modifying a glassy carbon electrode (GCE). This nanocomposite is promising to present a synergistic effect in the increase of the active surface area of the modified electrode to more load the biocapture of the target. Next, the RAC-binding aptamer (Apt) was attached to the AgNPs/QDs@GQDs/GCE surface and a sensitive layer for the RAC detection was embedded. A RAC-Apt complex was formed upon adding the RAC and the changes of the electrochemical behavior were studied by some electrochemical techniques such as electrochemical impedance spectroscopy (EIS). Under optimal conditions, the charge transfer resistance (Rct) value was increased linearly with increasing of the RAC concentrations in the range of 1 fM to 901.4 nM. Limit of detection (LOD) was calculated to be 330 aM which is superior by other reported electrochemical methods in the RAC sensing. The applicability of the aptasensor was tested in human urine and blood serum as the real samples and satisfactory results of specificity were achieved. It seems that the proposed strategy not only provides a new ultrasensitive strategy for RAC detection but also expands the application of the sensing interface to develop other aptasensors by changing the Apt sequence.
Impedimetric aptasensor for Pseudomonas aeruginosa by using a glassy carbon electrode modified with silver nanoparticles
Abstract
Impedimetric aptasensor for Pseudomonas aeruginosa by using a glassy carbon electrode modified with silver nanoparticles
An aptasensor is described for the ultrasensitive detection of Pseudomonas aeruginosa (P. aeruginosa). A glassy carbon electrode (GCE) was first modified by electrodeposition of silver nanoparticles (AgNPs). Immobilization of NH2-aptamer was covalently attached to the AgNP/GCE surface. The morphology, distribution and size of the sensor were characterized by field emission scanning electron microscopy. Cyclic voltammetry and electrical impedance spectroscopy were used to study conductivity of the aptasensor and the electrochemical properties. Detection of P. aeruginosa was carried out by evaluation of the charge transfer resistance after and before the adding of P.aeruginosa and by using the hexacyanoferrate redox system as an electrochemical probe. The impedance increases on going from 102 to 107 CFU·mL−1 concentrations of P. aeruginosa, and the detection limit is 33 CFU·mL−1 (for S/N = 3). The assay was successfully applied for the determination of P. aeruginosa in spiker serum samples.
The development of an electrochemical nanoaptasensor to sensing chloramphenicol using a nanocomposite consisting of graphene oxide functionalized with (3‐Aminopropyl) triethoxysilane and silver nanoparticles
Abstract
The development of an electrochemical nanoaptasensor to sensing chloramphenicol using a nanocomposite consisting of graphene oxide functionalized with (3‐Aminopropyl) triethoxysilane and silver nanoparticles
In the present research, a nanoaptasensor is proposed for electrochemical measurement of chloramphenicol (CAP). To this purpose, the nanocomposite prepared from graphene oxide and functionalized with (3‐Aminopropyl) triethoxysilane/silver nanoparticles to the abbreviated AgNPs/[NH2–Si]-f-GO, was utilized to modify the glassy carbon electrode (GCE). Furthermore, the modified electrode was also investigated using the electrochemical methods such as electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The AgNPs/[NH2–Si]-f-GO nanocomposite was investigated by UV–Vis spectrophotometry. Fourier transform infrared (FT-IR) spectrometry and transmission electron microscopy (TEM). Moreover, [Fe(CN)6]3-/4 solution in the role of an electrochemical probe was applied. The AgNPs/ [NH2–Si]-f-GO nanocomposite was confirmed as a good layer to covalent immobilization of aptamer (Apt) onto the GCE surface. In this sense, the DPV was used as a sensitive electrochemical technique for the measurement of CAP with an appropriate linear concentration range which was found to be between 10 pM and 0.2 μM and, with a low limit of detection, it equaled 3.3 pM. CAP which was identified in the presence of other usual antibiotics existed in the real samples.
Pd(II) and Pt(II) Metallacycles with Unsymmetrical Ylide: Antiproliferative Effects and Application in Electrocatalytic Oxidation of Methanol
Abstract
Pd(II) and Pt(II) Metallacycles with Unsymmetrical Ylide: Antiproliferative Effects and Application in Electrocatalytic Oxidation of Methanol
New Pd(II) and Pt(II) complexes are described in which the multidentate phosphorus ylides [Ph2P(CH2)nPPh2=C(H)C(O)C6H4‐p‐OCH3] (n=1, (Y1); n=2, (Y2)) act as P,C chelating ligands. The chelating ability of these ligands resulted in the formation of [MBr2{K2(P,C)‐Y1}] (M=Pd (1), Pt (2)); [MBr2{K2(P,C)‐Y2}] (M=Pd (3), Pt (4) complexes, which were investigated using physicochemical techniques. X‐ray diffraction studies of a single crystal of complex 2 confirmed the structure of the five‐membered ring. Owing to the redox activity of phosphorus‐ylide complexes, their electrocatalytic activity for the oxidation of methanol has been studied. All compounds were found to possess the anti‐proliferative potency against MCF‐7 (breast carcinoma), A549 (non‐small lung carcinoma) and AGS (gastric carcinoma) cell lines with average IC50 values in the range of 14.53 to 287.92 μM. In general, the compounds Y1, Y2, 2, and 3 displayed high anticancer activities compared to 1 and 4. The antioxidant activity of the compounds, which was estimated by 1, 1‐diphenyl‐2‐picryl‐hydrazyl (DPPH) free radical scavenging, was moderate to strong with IC50 values in the range 0.18 to 0.59 mg mL−1.
A nano-sized chitosan particle based electrochemical aptasensor for sensitive detection of P. aeruginosa
Abstract
A nano-sized chitosan particle based electrochemical aptasensor for sensitive detection of P. aeruginosa
In this research, a glassy carbon electrode (GCE) was modified with nano-sized chitosan particles (NCs) by the drop-casting method for ultrasensitive detection of Pseudomonas aeruginosa (P. aeruginosa). NCs act as a novel platform for the aptamer-based sensor (aptasensor) for sensitive and simultaneous detection of P. aeruginosa. This system is based on a P. aeruginosa-binding aptamer, which is covalently connected to the surface of the GCE which has been in turn modified by the NC in order to form a sensitive layer and improve the performance of the aptasensor. In order to investigate the conductivity of the aptasensor and its electrochemical properties, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques were used. A low detection limit of 3 CFU mL1 , wide linearity of 101 –107 CFU mL1 for the detection of P. aeruginosa and high sensitivity for the aptasensor, which are obtained under optimized conditions, have been proposed. To detect P. aeruginosa in blood serum samples, the prepared aptasensor was successfully applied. This aptasensor also showed excellent stability with satisfactory electrochemical performance, reproducibility, and selectivity.
Impedimetric ultrasensitive detection of chloramphenicol based on aptamer MIP using a glassy carbon electrode modified by 3-ampy-RGO and silver nanoparticle
Abstract
Impedimetric ultrasensitive detection of chloramphenicol based on aptamer MIP using a glassy carbon electrode modified by 3-ampy-RGO and silver nanoparticle
In this research work, a biosensor with a dual recognition system was fabricated and founded on a combination of aptasensing and the molecular imprinting union of the chloramphenicol (CAP) selective detection. CAP, is an antibiotic, was applied in veterinary and human in order to treat gram-positive and gram-negative infections. It is worth mentioning that CAP residue brings about earnest side effects on human health. According to this, in this sensing system, 3-aminomethyl pyridine functionalized graphene oxide (GO) (3-ampy-RGO) has been coated on the surface of GCE. Afterwards, the silver nanoparticle (AgNPs) was coated on the 3-ampy-RGO/GCE and, then, the CAP complex-amino-aptamer (NH2-Apt[CAP]) was attached to the AgNP/3-ampy-RGO/GCE using a kind of bonding formation of Ag-N. In this sense, it is worth noting that the resorcinol electropolymerization around the complex of aptamer/CAP would confine the complex and, then, retain the aptamer. Following the CAP removal, the MIP cavity, as it was supposed, synergistically acted with that of the embedded aptamer in order to construct a nanohybrid receptor. Interestingly, the double exact property of the molecular imprinting polymers and aptamers led to the superb sensing properties. In the mentioned system it was illustrated that the linear range was from 1.0 pM to 1.0 nM with the detection limit of 0.3 pM; consequently, as observed, it was better than or as good as other similar assays. Moreover, the mentioned system whose activity was observed in the various interferences presence showed great selectivity in detected the CAP. Finally, the designed sensor exhibited outstanding results when applied to detect CAP in milk samples.
Highly sensitive electrochemical determination of 5-fluorouracil using CuNPs/MWCNT/IL/Chit composite modified glassy carbon electrode
Abstract
Highly sensitive electrochemical determination of 5-fluorouracil using CuNPs/MWCNT/IL/Chit composite modified glassy carbon electrode
A fast and facile electrochemical sensor for detection of important anti-cancer drug 5- fluorouracil (5-FU) is fabricated using a copper-nanoparticles decorated multi-walled carbon nanotube and chitosan composite modified electrode. Copper nanoparticles/multi-walled carbon nanotubes/ionic liquid/chitosan modified glassy carbon electrode (CuNPs/MWCNTs/IL/Chit/GCE) prepared by the consecutive coating of MWCNTs/IL/Chit nanocomposite on the GCE, followed by the electrodeposition of copper. Surface characteristics of the modified electrode were studied by scanning electron microscopy (SEM). The electrochemical capability of the fabricated modified electrode for the detection of 5-FU is examined by cyclic voltammetry, differential pulse voltammetry (DPV). The nano Cu decorated MWCNTs/IL/Chit/GCE is found to be efficient for the electrocatalytic oxidation of 5-FU. The peak current of the DPV exhibited a linear relationship against 5-FU over a wide concentration range of 1-110 µM with a low detection limit (0.15 µM). Additional, the sensor was successfully applied in biological fluid sample analysis.
Development of an electrochemical aptasensor based on the gold nanorods and its application for detection of aflatoxin B1 in rice and blood serum samples
Abstract
Development of an electrochemical aptasensor based on the gold nanorods and its application for detection of aflatoxin B1 in rice and blood serum samples
Aflatoxins are a group of fungal mycotoxins produced mainly by molds; e.g., Aspergillus flavus and Aspergillus parasiticus. Among Aflatoxins, Aflatoxin B1 (AFB1) is the most toxic one. Therefore, there is a prompt need for determination of AFB1 in food products. This paper reports an electrochemical aptasensor for accurate determination of AFB1, which was constructed using gold nanorod sensing interface and aptamer as a specific recognition element. The synthesized gold nanorod was characterized by transmission electron microscopy, and the electrochemical behavior of fabricated aptasensor was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Under optimized conditions, the detection limit of the proposed aptasensor was 0.3 pM with dynamic range of 1.0 pM – 0.25 nM. This aptasensor represents a remarkable improvement in terms of sensitivity, selectivity, reproducibility and stability compared to the other methods for the determination of AFB1. This proposed sensor was successfully applied for the analysis of AFB1 in rice and blood serum samples.
The potentiality of graphene quantum dots functionalized by nitrogen and thiol-doped (GQDs-N-S) to stabilize the antibodies in designing of human chorionic gonadotropin immunosensor
Abstract
The potentiality of graphene quantum dots functionalized by nitrogen and thiol-doped (GQDs-N-S) to stabilize the antibodies in designing of human chorionic gonadotropin immunosensor
In this study, for the first time, a simple immunosensor for ultrasensitive recognition of human chorionic gonadotropin (HCG) in serum samples was fabricated using a simple approach. In this method, a low-cost, sensitive immunosensor was made based on QDs-N-S/Au nanoparticles (NPs) modified screen-printed carbon electrode (SPCE). It seems that QDs-N-S/AuNPs/ antibody as a biocomposite can be a good choice for development as an impressive immunosensor. In modifying the proposed immunosensor, the length of the process was reduced and the use of other substrates was eliminated. The pH and incubation time were optimized as two important parameters. Under the optimal conditions at modified SPCE, a linear communication in the range of 0.1 to 125 pg mL−1 and the detection limit of 12.5 fg mL−1 were obtained. The present procedure was utilized to the detection of HCG in real samples with the desirable results
Ti(IV) ion-imprinted polymer as a new selective sorbent for extraction and pre-concentration of trace amounts of titanium ions in different samples
Abstract
Ti(IV) ion-imprinted polymer as a new selective sorbent for extraction and pre-concentration of trace amounts of titanium ions in different samples
In this paper, a novel, simple, selective and effective solid phase extraction method based on ion-imprinted polymer (IIP) technology and flame atomic absorption spectrometry (FAAS) for separation and pre-concentration of trace amounts of titanium (IV) ions was reportd. It was obtained by precipitation polymerisation by using 2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxychromen-4-one titanium (IV) complex abbrivated as Ti(IV)-(morin), as the template molecule. After polymerisation, leaching the polymer in HNO3 (50% (v/v) solution caused formation cavities in the polymer. Characterisation studies of the Ti(IV)-imprinted polymer (Ti-IP) was performed by FT-IR, UV-Vis and scanning electron microscopy- energy-dispersive X-ray spectroscopy (SEM-EDS) techniques and then, the effective factors on extraction were optimised. A sensitive response to Ti(IV) within a concentration range between 0.01 and 4.0 μg mL−1 was achieved under the optimum conditions. A total of 10.0 ng mL−1 and 80.0 mg g−1 were obtained as limit of detection (LOD, 3Sb/m) and maximum adsorption capacity, respectively. The relative standard deviation (RSD) for eight replicates detections of 0.2 μg mL−1 of Ti(IV) was found to be 2.8%. By this method, pre-concentration factor (PF) of 100 was obtained. Successfully applying this method in the water and standard samples, reasonable results were obtained for the extraction and pre-concentration of the titanium ions.
Fabrication of novel metanil yellow/multi wall carbon nanotubes-chitosan/ modified glassy carbon electrode and its application for sensitive determination of persulfate
Abstract
Fabrication of novel metanil yellow/multi wall carbon nanotubes-chitosan/ modified glassy carbon electrode and its application for sensitive determination of persulfate
A new intensely-sensitive amperometric sensor applied for the rapid and accurate detection of persulfate and based on the modification of glassy carbon electrode (GCE) by multi-wall carbon nanotubes-chitosan (MWCNTs- Chit) nanocomposite and metanil yellow (MY) is fabricated. In this sense, MY which can be used as an excellent redox mediator can also catalyze the reduction of persulfate. The presence of MWCNTs-Chit nanocomposite can provide associated sites for the electrode position of MY on the electrode surface due to the high surface area. Moreover, it can also accelerate the rate of electron-transfer between MY film and the electrode due to its good catalytic capability. Combining these materials as modifiers caused the prepared MY/MWCNTs-Chit/GC electrode to display a linear amperometric respond to the persulfate concentration from 100 nM to 1.0 mM with a sensitivity of 860.1 nAnM−1 and a limit of detection (S/N=3) of 0.03 μM. The proposed sensor is successfully applied for the determination of persulfate in river water samples with satisfactory results.
An electrochemical tyrosinamide aptasensor using a glassy carbon electrode modified by N-acetyl-L-cysteine-capped Ag-In-S QDs
Abstract
An electrochemical tyrosinamide aptasensor using a glassy carbon electrode modified by N-acetyl-L-cysteine-capped Ag-In-S QDs
This paper reports an aptamer-based green approach for the electrochemical evaluation of tyrosinamide (Tyr- NH2). In this regard, at the first step, an aqueous synthetic strategy for preparing N-acetyl-L-cysteine (NAC)- capped Ag-In-S (AIS) quantum dots (QDs) with bright yellow/orange emission was developed. The conjugation of AIS QDs to NAC-biomolecules provides opportunities for using them as luminescent contrast agents for living cell tracking and labeling or sensing studies. In the next step, the design stage of the aptasensor, the glassy carbon electrode (GCE) was modified with the AIS QDs and then the Tyr-NH2 special aptamer, which has an amine group at its end, interacts with silver and indium ions at the surface of the AIS QDs and through the formation of covalent bonding of AgeN and IneN, attaches to the GCE surface modified with the AIS QDs. In this approach, for the first time, NAC-capped AIS QDs have been used to modify the electrode surface in the aptamerbased electrochemical sensor. The response changes of the [Fe(CN)6]4−/3− as redox probe, during the modification of GCE surface, the fabrication and assessment of proposed aptasensing, using the cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy were recorded. The designed aptasensor for the Tyr-NH2 evaluation showed good linearity from 0.01 to 2.81 nM and 2.81–10.81 nM, and low detection limit of 3.34 pM. The obtained results of the stability, reproducibility and selectivity investigations implying that the reported aptasensor as the first aptamer-based electrochemical assay for Tyr-NH2, can be reliable for the determination of Tyr-NH2 in serum samples.
Developing a four-dimensional voltammetry as a powerful electroanalytical methodology for simultaneous determination of three colorants in the presence of an uncalibrated interference
Abstract
Developing a four-dimensional voltammetry as a powerful electroanalytical methodology for simultaneous determination of three colorants in the presence of an uncalibrated interference
This paper reports an aptamer-based green approach for the electrochemical evaluation of tyrosinamide (Tyr- NH2). In this regard, at the first step, an aqueous synthetic strategy for preparing N-acetyl-L-cysteine (NAC)- capped Ag-In-S (AIS) quantum dots (QDs) with bright yellow/orange emission was developed. The conjugation of AIS QDs to NAC-biomolecules provides opportunities for using them as luminescent contrast agents for living cell tracking and labeling or sensing studies. In the next step, the design stage of the aptasensor, the glassy carbon electrode (GCE) was modified with the AIS QDs and then the Tyr-NH2 special aptamer, which has an amine group at its end, interacts with silver and indium ions at the surface of the AIS QDs and through the formation of covalent bonding of AgeN and IneN, attaches to the GCE surface modified with the AIS QDs. In this approach, for the first time, NAC-capped AIS QDs have been used to modify the electrode surface in the aptamerbased electrochemical sensor. The response changes of the [Fe(CN)6]4−/3− as redox probe, during the modification of GCE surface, the fabrication and assessment of proposed aptasensing, using the cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy were recorded. The designed aptasensor for the Tyr-NH2 evaluation showed good linearity from 0.01 to 2.81 nM and 2.81–10.81 nM, and low detection limit of 3.34 pM. The obtained results of the stability, reproducibility and selectivity investigations implying that the reported aptasensor as the first aptamer-based electrochemical assay for Tyr-NH2, can be reliable for the determination of Tyr-NH2 in serum samples.
Exploring the binding mechanism of saccharin and sodium saccharin to promoter of human p53 gene by theoretical and experimental methods
Abstract
Exploring the binding mechanism of saccharin and sodium saccharin to promoter of human p53 gene by theoretical and experimental methods
In the past few decades, extensive discussions have been on the impact of artificial sweeteners on the risk of cancer. The present study aimed to evaluate the interaction of saccharin (SA) and sodium saccharin (SSA) with the promoter of the human p53 gene. The binding ability was assessed using the spectroscopic technique, molecular docking and molecular dynamics (MD) simulation methods. Free energy of binding has been calculated using Molecular Mechanics/Poisson–Boltzmann Surface Area (MM/PBSA) method. Fluorescence spectra of mentioned gene with concentration profiles of SA and SSA were obtained in a physiological condition. A gradual increase without any significant spectral shift in the fluorescence intensity of around 350 nm was evident, indicating the presence of an interaction between both compounds and gene. The docking results showed that both compounds were susceptible to bind to 50 -DG56DG57-30 nucleotide sequence of gene. Furthermore, the MD simulation demonstrated that the binding positions for SA and SSA were 50 -A1T3T4-30 and 50 -G44T45-30 sequences of gene, respectively. The binding of these sweeteners to gene made significant conformational changes to the DNA structure. Hydrogen and hydrophobic interactions are the major forces in complexes stability. Through the groove binding mode, the non-interactive DNA-binding nature of SSA and SA has been demonstrated by the results of spectrofluorometric and molecular modeling. This study could provide valuable insight into the binding mechanism of SA and its salt with p53 gene promoter as macromolecule at the molecular level in atomistic details. This work can contribute to the possibility of the potential hazard of carcinogenicity of this sweetener and to design and apply new and safer artificial sweeteners.
Preparation of modified glassy carbon electrode by the use of titanium oxide, copper and palladium nanoparticles and its application for the electrocatalytic and photelectrocatalytic reduction of hydrogen peroxide
Abstract
Preparation of modified glassy carbon electrode by the use of titanium oxide, copper and palladium nanoparticles and its application for the electrocatalytic and photelectrocatalytic reduction of hydrogen peroxide
A new electrochemical sensor for hydrogen peroxide (H2O2) determination was fabricated based on less expensive and simple layer-by-layer method. The morphological and elemental characteristics of palladium, copper and titanium oxide nanoparticles modified glassy carbon electrode (GCE) were examined using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), respectively. The electrochemical behaviors of H2O2 on constructed sensor were investigated by cyclic voltammetry and amperometry techniques. By integration of the palladium, copper and titanium oxide nanoparticles into the nanocomposite, the constructed nanocomposite illustrated good synergistic effect in reduction of H2O2, thereby resulting in the higher cathodic peak current and very reduced over potential. The sensor displays a fast response time less than 2 s with a linear range from 0.05 µM to 0.1 M and detection limit of 16.0 nM (S/N=3). Moreover, the photoelectrocatalytic capability of the proposed modified electrode was explored in dark and under light irradiation conditions. The catalytic current significantly increased under illumination condition and it comes back to its original value by turning off the light irradiation. This result indicates the stable photo-induced catalytic behavior of the constructed sensor. The resulting sensor was successfully used to detection of hydrogen peroxide in real samples.
An electrochemical aptasensor for streptomycin based on covalent attachment of the aptamer onto a mesoporous silica thin film-coated gold electrode
Abstract
An electrochemical aptasensor for streptomycin based on covalent attachment of the aptamer onto a mesoporous silica thin film-coated gold electrode
An electrochemical method is described for the determination of streptomycin (STR). It is making use of a gold electrode coated with a thin mesoporous silica film (MSF). In addition, silver nanoparticles were coated on the MSF to increase the surface area, to bind a large amount of aptamer (Apt), and to improve the electrical conductivity. In the presence of STR, it will bind to the Apt and hinder the diffusion of the redox probe hexacyanoferrate through the nanochannels of the mesoporous film. The aptasensor, best operated at a working potential of 0.22 V (vs. Ag/AgCl) has a linear response in the 1 fg.mL−1 to 6.2 ng.mL−1 STR concentration range. The detection limit is 0.33 fg.mL−1 . The assay was successfully validated by analyzing spiked samples of milk and blood serum.
Synthesis, characterization, anticancer properties and theoretical study of asymmetrical Cd(II)–N2-Schiff base complexes
Abstract
Synthesis, characterization, anticancer properties and theoretical study of asymmetrical Cd(II)–N2-Schiff base complexes
In this study, synthesis, characterization and anticancer properties of four cadmium(II) complexes of a new asymmetrical bidentate Schiff base ligand (abbreviated as L) with a CdLX2 (X = Cl−, Br−, I− and SCN−) general formula are reported. The ligand and its complexes were characterized by elemental analysis, molar conductance, UV–Vis, FT-IR, 1H NMR and 13C NMR spectra. Coordination of the ligand was confirmed by consistent changes in FT-IR and NMR spectra when compared with the spectra of free ligand. Redox properties of ligand and complexes were investigated by the electrochemical method, cyclic voltammetry. Also, changes in the cathodic and anodic peaks potentials of complexes regarding free ligand, confirm synthesis of complexes. All complexes correspond to Cd(II)/Cd(0) system show one pair anodic and cathodic peaks. The density function theory calculations are used to investigate the electronic structures of the ligand and its complexes. In vitro anticancer activity of ligand and complexes was studied on cancer cells lines HT29 and A549. Obtained data confirmed the potent cytotoxic activity in the chloro and bromo substituted Cd(II) complexes when compared with free ligand, control sample and other Cd(II) compounds. The IC50 values for ligand and complexes were approximately less than 0.1 mg mL−1.
Development of electrochemical sensor based on molecularly imprinted copolymer for detection of nitrofurantoin
Abstract
Development of electrochemical sensor based on molecularly imprinted copolymer for detection of nitrofurantoin
The present study aimed to identify and analyze how an imprinted molecularly sensor was used for a direct determination of nitrofurantoin (NFT). The polymerization was directly performed on the surface of glassy carbon electrode by m-dihydroxybenzene and o-aminophenol as monomers. In this regard, the most fundamental issue to be noticed was the special porous forms which, after being washed, were obtained for the NFT molecule. Accordingly, great selectivity and high sensitivity to detect NFT were observed. The proposed system showed good linearity ranging from 0.001 to 0.05 and 0.1 to 1.0 µM, with a detection limit of 0.3 nM. Finally, it should also be noted that the proposed sensor was very selective and sensitive for the detection of NFT in the real serum samples.
Development of Electrochemical Sensor Based on Glassy Carbon Electrode Modified with a Molecularly Imprinted Copolymer and its Application for Detection of Repaglinide
Abstract
Development of Electrochemical Sensor Based on Glassy Carbon Electrode Modified with a Molecularly Imprinted Copolymer and its Application for Detection of Repaglinide
At the present study, we have reported a new sensor based on immobilized molecularly imprinted polymer on the surface of a glassy carbon electrode (GCE) through electro polymerization of o‐Dihydroxybenzene (o‐DB) and o‐phenylenediamine (o‐PD) as monomers for direct determination of repaglinide (RPG) as target molecule. RPG is a new generation of oral anti‐diabetic drugs that has a rapid onset of action and short half‐life of approximately 1 h. So developing a controlled system with good sensitivity and selectivity is required to eliminate its adverse effects. Under the optimized conditions, the proposed sensor showed a good selectivity to detect RPG among compounds with similar structure and properties with RPG. The linear range for analysis were 0.005–1.0 μM and detection limit 1.8 nM was achieved. Furthermore, the experimental results showed that the proposed sensor was highly selective and sensitive to detect RPG in real samples such as blood serum, urine and RPG tablet.
A glassy carbon electrode with electrodeposited silver nanoparticles for aptamer based voltammetric determination of trinitrotoluene using riboflavin as a redox probe
Abstract
A glassy carbon electrode with electrodeposited silver nanoparticles for aptamer based voltammetric determination of trinitrotoluene using riboflavin as a redox probe
An electrochemical nanoaptasensor is described that is based on the use of a glassy carbon electrode (GCE) modified with electrodeposited silver nanoparticles (AgNPs). An aptamer (Apt) against trinitrotoluene (TNT) was then immobilized on the AgNPs. The addition of TNT to the modified GCE leads to decrease in peak current (typically measured at a potential of −0.45 V vs. Ag/AgCl) of riboflavin which acts as an electrochemical probe. Even small changes in the surface (as induced by binding of Apt to TNT) alter the interfacial properties. As a result, the LOD is lowered to 33 aM, and the dynamic range extends from 0.1 fM to 10 μM without sacrificing specificity
Applicability of AuNPs@N-GQDs nanocomposite in the modeling of the amplified electrochemical Ibuprofen aptasensing assay by monitoring of riboflavin
Abstract
Applicability of AuNPs@N-GQDs nanocomposite in the modeling of the amplified electrochemical Ibuprofen aptasensing assay by monitoring of riboflavin
Here, an ultrasensitive and low-cost electrochemical aptasensing assay is developed based on the applicability of a fabricated nanocomposite from nitrogen-doped graphene quantum dots (N-GQDs) and gold nanoparticles (AuNPs). A modified glassy carbon electrode (GCE) with the AuNPs@N-GQDs nanocomposite (AuNPs@ N-GQDs/GCE) as an efficient platform has some unique properties such as high surface area and electrical conductivity. Furthermore, the prepared platformis capable of more loading of aptamer (Apt)molecules as a biological recognition element of Ibuprofen (IBP) on the modified electrode surface. It is noteworthy that in this study, riboflavin (RF) as a universal green probe is used for the first time for electrochemical detection of IBP. According to the proposed strategy and under the optimum condition, the unprecedented detection limit (LOD) of this assay (33.33 aM) is lower than previously reported analytical methods. The results demonstrate the ability of the nanocomposite for designing of the aptasensor, integrated within the electrode format, to cheaper and simpler detection of the IBP with a specificity and sensitivity sufficient for analysis in real samples. It seems that the proposed strategy based on the AuNPs@N-GQDs nanocomposite can be expanded to other nanomaterials. So, this is expected to have promising implications in the design of electrochemical sensors or biosensors for the detection of various targets.
An electrochemical chlorpyrifos aptasensor based on the use of a glassy carbon electrode modified with an electropolymerized aptamer-imprinted polymer and gold nanorods
Abstract
An electrochemical chlorpyrifos aptasensor based on the use of a glassy carbon electrode modified with an electropolymerized aptamer-imprinted polymer and gold nanorods
A highly selective and sensitive aptasensor is described for voltammetric determination of the pesticide chlorpyrifos (CPS). The sensor was constructed by modifying a glassy carbon electrode (GCE) with gold nanorods and a polymer that was molecularly imprinted with an aptamer against CPS. This results in double specific recognition. Under optimal conditions and a working potential as low as 0.22 V (vs. Ag/AgCl), the nanotools has a dynamic range that covers the 1.0 fM - 0.4 pM CPS concentration range, and the detection limit is 0.35 fM. This is lower than any of the previously reported methods. This MIP-aptasensor is selective over structural analogs, stable, and adequately reproducible. It was successfully applied to the determination of CPS in spiked food samples.
A novel aptasensor based on gold nanorods/ZnS QDs-modified electrode for evaluation of streptomycin antibiotic
Abstract
A novel aptasensor based on gold nanorods/ZnS QDs-modified electrode for evaluation of streptomycin antibiotic
In this study, a simple and effective strategy was developed for specific detection of streptomycin (STR) antibiotic. At first, in this strategy, glassy carbon electrode (GCE) was covered by thiourea capped-ZnS QDs and gold nanorods (AuNRs) for the construction of a sensing interface for thiolated aptamer immobilization. Subsequently, the STR thiol-aptamer was covalently attached on the AuNRs/thiourea capped-ZnS QDs/GCE via Au–S bond formation. Morphology of the modified electrode was characterized via emission scanning electron microscopy (FE-SEM) technique. The proposed system showed good linearity ranging from 1 fg mL1 to 1.111 pg mL1 and 1.111 pg mL1 to 11.1111 ng mL1 , with a detection limit of 0.35 fg mL1 . Furthermore, this methodology was also applied to evaluate STR in milk and serum samples, indicating the feasibility of the application of aptasensor analysis for STR detection. The presented system, in presence of different interferences, indicated good selectivity in detecting the STR. Our study provides a facile and low-cost method for designing aptamer-based sensors toward the evaluation of other antibiotics if the specific aptamer is available.
MATLAB in electrochemistry: A review
Abstract
MATLAB in electrochemistry: A review
MATLAB (MATrix LABoratory) is a multi-paradigm numerical computing environment and fourth-generation programming language. MATLAB allows matrix manipulations, plotting of functions and data, implementation of algorithms, creation of user interfaces and interfacing with programs written in other languages, including C, C++, Java, Fortran and Python. Electrochemistry is a branch of chemistry that studies the relationship between electricity, as a measurable and quantitative phenomenon, and identifiable chemical change, with either electricity considered an outcome of a particular chemical change or vice versa. MATLAB has obtained a wide range of applications in different fields of science and electrochemists are also using it for solving their problems which can help them to obtain more quantitative and qualitative information about systems under their studies. In this review, we are going to cast a look on different applications of MATLAB in electrochemistry and for each section, a number of selected articles published in the literature will be discussed and finally, the results will be summarized and concluded.
A novel electrochemical sensor based on electrode modi ed with gold fi nanoparticles and molecularly imprinted polymer for rapid determination of trazosin
Abstract
A novel electrochemical sensor based on electrode modi ed with gold fi nanoparticles and molecularly imprinted polymer for rapid determination of trazosin
A novel molecularly imprinted polymer sensor for fast and direct determination of trazosine (TR) was studied. The voltammetric sensor based on molecularly imprinted polymer (MIP) with disposable gold nanoparticles modi ed screen printed carbon electrode (MIP/AuNPs/SPCE) is developed for the determination of TR. Under fi the optimum conditions, the peak current of the sensor and TR concentration showed a good linear relationship over the range from 2.0 to 250.0 M, with a low detection limit (S/N = 3) of 0.3 M. The modi ed electrode μ μ fi demonstrated good electrocatalytic properties toward the oxidation of TR. This sensor selectively detected TR even in the presence of high concentration of similar compounds and MIP/AuNPs/SPCE was also con rmed fi successfully for the determination of TR in the various real samples including human blood serum, urine and trazosin tablet.
An aptasensor for voltammetric and impedimetric determination of cocaine based on a glassy carbon electrode modified with platinum nanoparticles and using rutin as a redox probe
Abstract
An aptasensor for voltammetric and impedimetric determination of cocaine based on a glassy carbon electrode modified with platinum nanoparticles and using rutin as a redox probe
We describe a method for the determination of cocaine that is based on a glassy carbon electrode modified with a nanocomposite consisting of multiwalled carbon nanotubes, an ionic liquid, and chitosan. The electrode was made cocaineresponsive by immobilizing a cocaine-specific aptamer and platinum nanoparticles (PtNPs) on the modified electrode. The use of PtNPs resulted in the acceleration of the electron transfer kinetics of the reduction of the redox probe rutin and enhances sensitivity. The sensor, best operated at a working voltage of 260 mV vs. Ag/AgCl, has a linear response to cocaine in the 1 nM to 11 μM concentration range, and the detection limit is 100 pM (at an S/N ratio of 3). We think this strategy to represent a promising platform for the sensitive and selective determination of cocaine. The sensor is adequately stable and was successfully applied to the determination of cocaine in spiked serum.
Synthesis, characterization, anticancer properties and theoretical study of asymmetrical Cd(II)eN2-Schiff base complexes
Abstract
Synthesis, characterization, anticancer properties and theoretical study of asymmetrical Cd(II)eN2-Schiff base complexes
In this study, synthesis, characterization and anticancer properties of four cadmium(II) complexes of a new asymmetrical bidentate Schiff base ligand (abbreviated as L) with a CdLX2 (X ¼Cl-, Br-, I- and SCN-) general formula are reported. The ligand and its complexes were characterized by elemental analysis, molar conductance, UVeVis, FT-IR, 1H NMR and 13C NMR spectra. Coordination of the ligand was confirmed by consistent changes in FT-IR and NMR spectra when compared with the spectra of free ligand. Redox properties of ligand and complexes were investigated by the electrochemical method, cyclic voltammetry. Also, changes in the cathodic and anodic peaks potentials of complexes regarding free ligand, confirm synthesis of complexes. All complexes correspond to Cd(II)/Cd(0) system show one pair anodic and cathodic peaks. The density function theory calculations are used to investigate the electronic structures of the ligand and its complexes. In vitro anticancer activity of ligand and complexes was studied on cancer cells lines HT29 and A549. Obtained data confirmed the potent cytotoxic activity in the chloro and bromo substituted Cd(II) complexes when compared with free ligand, control sample and other Cd(II) compounds. The IC50 values for ligand and complexes were approximately less than 0.1mgmL-1.
Dual detection of Malation and Hg (II) byfluorescence switching of graphene quantum dots
Abstract
Dual detection of Malation and Hg (II) byfluorescence switching of graphene quantum dots
The present study investigates sensitive and selective“off–on” method to analyze and detect mercury ions (Hg 2+ ) and Malation pesticide using graphene quantum dots (GQDs) as a new fluorescent (FL) probe. When GQDs are present, Hg 2+ cations are capable of being coordinated on the GQD surface by their negatively charged surface. The process of absorption occurs using electrostatic interactions. Hence, the FL of the GQDs would be remarkably quenched (turn-off) at 463 nm for 1μMHg2+ as a result of FL charge transfer. Nevertheless, when 40 μM of Malation is added to the GQDs-Hg 2+ solution, the FL of the GQDs enhances significantly at 463 nm (turnon), since Hg 2+ is combined with SR- group in the Malation rather than with the GQDs in the aqueous solution. Instead of the weak electrostatic interaction, a strong metal-thiol bond interaction is formed between Hg 2+ and Malation and an enhancement in the FL of GQDs is observed. Finally, acceptable linearity for Hg 2+ and Malation detection is obtained in the concentration ranges of 1–10μM and 10–80 for Hg 2+ and linear range of 80–120μM for Malation with an LOD of 0.5 μM and R 2 = 0.99.
Designing of some platinum or palladium-based nanoalloys as effective electrocatalysts for methanol oxidation reaction
Abstract
Designing of some platinum or palladium-based nanoalloys as effective electrocatalysts for methanol oxidation reaction
Nano alloys contain noble metal nanostructures exhibit a wide theoretical and experimental interest in the field of fuel cells. Hard endeavors have been enhanced to improve the catalytic performance and minimize the usage of precious metals by alloying them with non-precious ones. Formation of bimetallic and trimetallic noble metal alloys with well-designed structures provide the opportunity to reach this goal. In this study, we first discuss the synthesis of noble metal alloy nanostructured thin films such as PtCu, PdCu, PtCu/reduced-graphene oxide (RGO), PdCu/RGO, PtCo, PtCo/RGO, PtPdCu and PtPdCu/RGO viaa simple reduction of organometallic precursors including [PtCl2(cod)] and [PdCl2(cod)], (cod ¼ cis, cis-1,5-cyclooctadiene), in the presence of [Cu(acac)2] and [Co(acac)3](acac ¼acetylacetonate) at oil/water interface and room temperature, including nanoparticles and nanosheets. Then the effects of the well-defined nanostructures on the improved electrochemical properties are outlined. Finally, we conclude that these nonprecious bi and trimetallic alloy nanostructured thin films have better electrocatalytic performance than Pt monometallic thin films and other Pt nanostructures due to the geometric, electronic and stabilizer effect.
Using Boehmite Nanoparticles as an Undercoat, and Riboflavin as a Redox Probe for Immunosensor Designing: Ultrasensitive Detection of Hepatitis C Virus Core Antigen
Abstract
Using Boehmite Nanoparticles as an Undercoat, and Riboflavin as a Redox Probe for Immunosensor Designing: Ultrasensitive Detection of Hepatitis C Virus Core Antigen
In this study, a label -free electrochemical immunosensor for ultrasensitive detection of Hepatitis C virus core antigen in serum samples was fabricated using a simple approach. In this method, a low- cost and sensitive immunosensor was fabricated based on a boehmite nanoparticles (BNPs) modified glassy carbon. The BNPs provide a specific platform with an increased surface area which is capable of loading more antibody molecules as a receptor element of Hepatitis C virus core antigen on the electrode surface. It seems that BNP/ antibody conjugate may be an ideal platform for the development of an efficient immunosensor. It is worth noting that the proposed nanoimmunosensor combines the advantages of the elimination of another substrates in modifying the electrode and reducing the length of the modifying process. The experimental parameters, such as pH and incubation of time were optimized. Und er the optimal conditions for modified glassy carbon electrode, a linear relationship was realized in the range of 0.08- 110 pg ml -1 , with the detection limit of 10 fg ml -1 . The proposed method was applied to the determination of Hepatitis C virus core antigen in serum samples with the desirable results.
Applicability of the Dendrimer-quantum Dot (Den- QD) Bioconjugate as a Novel Nanocomposite for Signal Amplification in the Fabrication of Cocaine Aptasensor
Abstract
Applicability of the Dendrimer-quantum Dot (Den- QD) Bioconjugate as a Novel Nanocomposite for Signal Amplification in the Fabrication of Cocaine Aptasensor
A selective aptasensor was developed using the electrochemical transduction method for the ultrasensitive detection of cocaine. Inthis method, dendrimer-quantum dot (Den- QD) bioconjugate was utilized as a specific nanocomposite to efficiently fabricate the aptasensor. CdTe QD, which carries highly significant properties, was immobilized on the surface of a glassy carbon electrode (GCE), and polyamidoamine (PAMAM) dendrimer (Den) was covalently attached to the carboxyl-terminated surface of the CdTe QDs. This clever combination of QD and Den provides a highly stable matrix for the increased loading of aptamer (Apt)as a cocaine molecular receptor via covalent attachment. The Apt was functionalized with AuNPs leading to the amplification of the electrochemical signal. In this study, upon the incubation of cocaine on the aptasensor surface, the peak current of the redox probe decreased due to the hindered electron transfer reaction on the sensing surface. This study shows that the proposed aptasensor can detect cocaine by electrochemical impedance spectroscopy (EIS) technique at a linear range (5.00 10 -3 -6.00 nM) and a capability of detection down to 1.60 pM. The excellent specificity of this sensing system is demonstrated using some common analgesic drugs, and finally, the proposed aptasensor was successfully used to measure cocaine in the human serum sample. The proposed methodology may hold great promise for the design of other aptasensors and immunosensors based on the use of the Den-QD bioconjugate as a nanocomposite with high performance.
Polymerization of graphene oxide nanosheet by using of aminoclay: Electrocatalytic activity of its platinum nanohybrids
Abstract
Polymerization of graphene oxide nanosheet by using of aminoclay: Electrocatalytic activity of its platinum nanohybrids
This study describes the polymerization of graphene oxide (GO) nanosheet to reduced‐GO‐aminoclay (RGC) by covalent functionalization of chemically reactive epoxy groups on the basal planes of GO with amine groups of magnesium phyllosilicate clay (known as aminoclay). The resulting RGC sheets were characterized and applied to support platinum nanostructures at toluene/water interface. Pt nanoparticles (NPs) with diameters about several nanometers were adhered to RGC sheets by chemical reduction of [PtCl2(cod)] (cod = cis,cis‐1,5‐ cyclooctadiene) complex. Catalytic activity of Pt NPs thin films were investigated in the methanol oxidation reaction. Cyclic voltammetry results exhibit that the Pt/reduced‐GO (RGO) and Pt/RGC thin films showed improved catalytic activity in methanol oxidation reaction in comparison to other Pt NPs thin films, demonstrating that the prepared Pt/RGO and Pt/RGC thin films are promising catalysts for direct methanol fuel cell.
Facile synthesis of PtSnZn nanosheet thin film at oil–water interface by use of organometallic complexes: An efficient catalyst for methanol oxidation and p‐nitrophenol reduction reactions
Abstract
Facile synthesis of PtSnZn nanosheet thin film at oil–water interface by use of organometallic complexes: An efficient catalyst for methanol oxidation and p‐nitrophenol reduction reactions
PtSnZn nanosheet thin film with stable and high activity towards methanol electro‐oxidation was synthesized via a simple reduction of organometallic precursors including [PtCl2(cod)] (cod = cis,cis‐1,5‐cyclooctadiene) and [Sn(CH3)4] complexes, in the presence of [Zn(acac)2] (acac = acetylacetonate) complex at toluene–water interface. Catalytic activities of PtSnZn nanosheets were investigated in the p‐nitrophenol (p‐Nip) reduction and methanol oxidation reactions. The obtained results demonstrate that PtSnZn nanosheets exhibit a good electrocatalytic performance for methanol oxidation reaction, the catalytic activity of the PtSnZn nanosheets being at least 3.5 times higher than that of Pt nanoparticle thin film. Also, the apparent rate constant obtained for p‐Nip reduction with the PtSnZn nanosheets is at least 2.3 times higher than that for Pt nanoparticle thin film due to the appropriate interaction between platinum, tin and zinc metals and geometric properties of PtSnZn nanosheet thin film. Nanosheets are highly favourable for superior catalytic performances due to their geometric properties. A facile and efficient route was used to synthesize trimetallic alloy thin film at oil–water interface.
Application of ion-imprinted polymer synthesized by precipitation polymerization as an efficient and selective sorbent for separation and pre-concentration of chromium ions from some real samples
Abstract
Application of ion-imprinted polymer synthesized by precipitation polymerization as an efficient and selective sorbent for separation and pre-concentration of chromium ions from some real samples
In this study, a new Cr(III)-imprinted polymer (Cr(III)-IIP) is prepared from CrCl3·6H2O, methacrylic acid functional monomer, ethyleneglycoldimethacrylate cross-linking agent, 2,2ʹ-azobisisobutyronitrile radical initiator and 2,2-(azanediylbis (ethane-2,1-diyl))bis(isoindoline-1,3-dione) ligand. To obtain the maximum adsorption capacity, the optimum condition was studied through pH, type and concentration of eluent, IIP weight, sample volume as well as the adsorption and desorption times. The Cr(III) ion content was determined via flame atomic absorption spectrometer. In optimum conditions, the adsorption capacity of the IIP for Cr(III) was obtained to be 74.65 mg g−1, using 50 mg of IIP and the initial pH solution of 3.0. Both the adsorption and desorption times for quantitative analyses of Cr(III) ions were 15 and 5 min; respectively. After elution of the adsorbed ions by 3 mL of 4 mol L−1 HNO3 aqueous solution, the established IIP-based SPE procedure provides a reasonable pre-concentration factor of 100. The IIP-based pre-concentration method provides a low detection limit of 1.7 μg L−1 with good repeatability (RSD = 3.22%). Reusability studies confirmed that synthesis IIP is reusable and recoverable up to six cycles. According to the selectivity experiments, it was concluded that the prepared sorbent possesses more affinity toward Cr(III) ions than other ions such as Al3+, Pb2+, Cu2+, Mn2+, Fe2+, Zn2+, and Ni2+ ions. To evaluate the potential applicability of the proposed separation method, the pre-concentration and determination of trace amounts of Cr(III) were performed successfully in food samples with complex matrices, a bestial sample (i.e. cow liver) and an herbal product (i.e., broccoli) as real samples.
Designing an electrochemical aptasensor based on immobilization of the aptamer onto nanocomposite for detection of the streptomycin antibiotic
Abstract
Designing an electrochemical aptasensor based on immobilization of the aptamer onto nanocomposite for detection of the streptomycin antibiotic
Streptomycin (STR), an aminoglycoside antibiotic, was used in human and veterinary to treat gram-negative infections. STR residue causes serious side effects on human health. Accordingly, to achieve a novel and sensitive method for detection of STR, we attempted to develop electrochemical sensing system based on graphene quantum dots (GQDs) functionalized with amine (eNH) and thiol (eSH) groups (GQDs-N-S) as the promising newest carbon-based nanomaterial. In this sensing system, gold nanoparticle (AuNPs) was deposited on the GCE surface. Then GQDs-N-S was coated on the AuNPs/GCE surface. After, the silver nanoparticle (AgNPs) coated on the GQDs-N-S/AuNPs/GCE. Finally, the STR thiol-aptamer (SH-Apt) was covalently attached on the AgNPs/ GQDs-N-S/AuNPs/GCE via bonding formation of AgeS. This system showed linear range from 0.01 pg·mL−1 to 812.21 pg·mL−1 with limit of detection of 0.0033 pg·mL−1 ; it was as good as or better than other similar assays, and also the proposed system, in the presence of different interferences, displayed good selectivity in detecting STR. The proposed aptasensor showed excellent results in quantitatively the detection of STR in serum samples.
Impedimetric detection of cocaine by using an aptamer attached to a screen printed electrode modified with a dendrimer/silver nanoparticle nanocomposite
Abstract
Impedimetric detection of cocaine by using an aptamer attached to a screen printed electrode modified with a dendrimer/silver nanoparticle nanocomposite
The authors describe a highly sensitive method for the aptamer (Apt) based impedimetric determination of cocaine. The surface of a screen-printed electrode (SPE) was modified with a nanocomposite of dendrimer and silver nanoparticles (AgNPs). The cocaine-binding Apt was attached to a dendrimer/AgNP/SPE surface, forming a sensitive layer for the determination of cocaine. The incubation with the analyte resulted in the formation of a cocaine/Apt complex on the electrode surface. As a consequence, folding and conformational change in the aptamer structure was induced, this resulting in a change in the impedimetric signal. The aptaassay exhibits highly efficient sensing characteristics with a good linearity of 1 fmol L −1to 100 nmol L−1(with two linear ranges) and a limit of detection (LOD) of 333 amol L−1 . Its excellent specificity and high sensitivity suggest that this kind of aptamer-based assay may be applied to detect other targets in this field
Influence of amine group on the adsorptive removal of basic dyes from water using two nanoporous isoreticular Zn(II)-based metal organic frameworks
Abstract
Influence of amine group on the adsorptive removal of basic dyes from water using two nanoporous isoreticular Zn(II)-based metal organic frameworks
Dyes are the most abundant hazardous components existing in the environment because of their extensive use in industries. So, in the present study, two isoreticular Zn(II)-MOFs, TMU-16 and TMU-16-NH2, were used for the adsorptive removal of harmful cationic dyes from aquatic medium. In order to improve the removal efficiency, optimization of the experimental conditions was carried out as a function of pH, MOF dosage, dye concentration and contact time. The maximum removal capacity was obtained at pH 12, 10 mg of MOF and 20 min as the contact time. The adsorption isotherms of each dye over both sorbents matched with the Langmuir model, and the adsorption kinetics followed the pseudo-second order kinetic model. The dye adsorption over TMU-16-NH2 is higher than that over TMU-16, indicating that the addition of amine groups in MOF network played an important role in the adsorption process, because of electrostatic interactions and hydrogen bonding. Thermodynamic studies indicated that adsorption process is spontaneous and endothermic.
Ultra-sensitive aptasensor based on a GQD nanocomposite for detection of hepatitis C virus core antigen
Abstract
Ultra-sensitive aptasensor based on a GQD nanocomposite for detection of hepatitis C virus core antigen
In the present study, by using the aptamer proximity binding assay strategy, a novel electrochemical aptasensor is described for ultrasensitive detection of hepatitis C virus (HCV) core antigen. The immobilization surface is prepared by the modification of a glassy carbon electrode (GCE) with a graphene quantum dots (GQD). GQD were introduced as a novel and suitable substrate for aptamers through p-p stacking interactions, the richness of hydrophilic edges as well as hydrophobic plane in GQD which enhances the aptamer absorption on the electrode surface. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were performed at each stage of the chemical modification process to confirm the resulting surface changes. EIS technique was used as an efficient alternative detection system for HCV core antigen measurement with detection limit 3.3 pg mL1 and two linear concentration range 10e70 pg mL1 and 70e400 pg mL1. Moreover, the fabricated aptasensor could accurately detect HCV core antigen concentration in human serum samples. Such an aptasensor opens a rapid, selective and sensitive route for HCV core antigen detection and provides a promising strategy for potential applications in clinical diagnostics.
Preparation of Modified Magnetic Cobalt Nanoparticles as a New Magnetic Sorbent for the Preconcentration and Determination of Trace Amounts of Lead Ions in Environmental Water and Soil (Air-Dust) Samples
Abstract
Preparation of Modified Magnetic Cobalt Nanoparticles as a New Magnetic Sorbent for the Preconcentration and Determination of Trace Amounts of Lead Ions in Environmental Water and Soil (Air-Dust) Samples
In this study, cobalt magnetic nanoparticles (MNPs) were synthesized and then modified by sodium dodecyl sulfate (SDS) and 2-(5-bromo-2- pyridylazo)-5-diethyl aminophenol ligand (5-Br-PADAP), through a chemical precipitation method. Characterization of the prepared MNP adsorbents was performed by Fourier transform infrared and transmission electron microscopy. Cobalt nanoparticles (NPs) surface modified with SDS and 5-Br-PADAP was evaluated as a nanoparticulate solid-phase extraction (SPE) absorbent for lead ions Pb(II) from water and standard samples, prior to its flame atomic absorption spectrometry determination. Effects of pH, amount of sorbent, desorption solvent, adsorption time, desorption time, and interfering ion concentration on extraction efficiency were investigated. Under optimal conditions, the calibration curve was linear in the range of 1.0–500 ng mL−1of Pb(II) with R2 = 0.998. Detection limit was 1.6 ng mL−1 in the original solution (3Sb/m), and the relative standard deviation for replicate determination of 0.5 μg mL−1 Pb (II) was ±2.7%.
A novel electrochemical aptasensor for highly sensitive and quantitative detection of the streptomycin antibiotic
Abstract
A novel electrochemical aptasensor for highly sensitive and quantitative detection of the streptomycin antibiotic
In the present study,we report a facile approach to employ gold nanoparticle (AuNPs) and thiol graphene quantum dots (GQD-SH) as the nanomaterial for ultrasensitive detection of streptomycin (STR). Based on this strategy, a GQD-SH was immobilized onto the surface of a glassy carbon electrode (GCE). AuNPs have been immobilized on SH groups of GQDs through bonding formation of Au\\S and Apt have been loaded on the electrode surface through the interaction between thiol group of aptamer. By incubating STR as a target onto the surface of the prepared Apt/AuNPs/GQD-SH/GCE as a proposed nanoaptasensor, the Apt/STR complex was formed and the changes of the electrochemical signal were evaluated with the EIS technique. The proposed nanoaptasensor showed wide linear range from 0.1 to 700 pg ml−1. Finally, the proposed nanoaptasensor was successfully applied for the determination of STR in real samples and satisfactory results were obtained.
Determination of Trace Amounts of Cadmium Ions in Water and Plant Samples Using Ligand- Less Solid Phase Extraction-Based Modified Co3O4 Nanoparticles
Abstract
Determination of Trace Amounts of Cadmium Ions in Water and Plant Samples Using Ligand- Less Solid Phase Extraction-Based Modified Co3O4 Nanoparticles
In this study, a new Co3O4 nanoparticles (NPs) coated with sodium dodecyl sulphate (SDS) is developed for preconcentration of trace amounts of cadmium ions (Cd 2+) as a prior step to its determination by flame atomic absorption spectrometry (FAAS). The effects of various parameters, including pH of sample solution, amount of sorbent, flow rates of solution and eluent, sample volume, type, and least amount of the eluent for elution of the Cd 2+ from Co3O4 NPs were studied and optimized. Experimental conditions for effective separation of trace levels of the Cd 2+were optimized with respect to different experimental parameters in Column method. Under the best experimental conditions, the calibration curve was linear in the range of 1.0–500.0 ng.mL−1 of cadmium (Cd) with R2 = 0.999. The detection limit was 0.4ng.mL−1 in the original solution (3Sb/m) and the relative standard deviation for eight replicate determination of 0.1μg.mL−1 Cd was ±2.1%. The method was validated by the analysis of a certified reference material with the results being in agreement with those quoted by manufactures. The developed method was successfully applied to the extraction and determination of Cd in water and food samples with satisfactory results.
A nanohybrid probe based on double recognition of an aptamer MIPgrafted onto a MWCNTs-Chit nanocomposite for sensing hepatitis Cvirus core antigen
Abstract
A nanohybrid probe based on double recognition of an aptamer MIPgrafted onto a MWCNTs-Chit nanocomposite for sensing hepatitis Cvirus core antigen
In this research work, multi-walled carbon nanotubes-chitosan nanocomposite (MWCNTs-Chit) is uti-lized as a special immobilization interface to improve the conductivity and performance characteristicsof the sensors to increase the loading amount of aptamer (Apt) sequence. A novel sensor for the firsttime was constructed for hepatitis C virus (HCV) core antigen (Anti) through combining the benefitsaptasensing and molecular imprinting (MIP) approaches based on electropolymerization of dopamine(DA) around the Apt [HCV core antigen] complex on MWCNTs-Chit modified GCE. The sensor also can bea useful tool for detection of HCV core antigen with low response time, low cost, good sensitivity, and highstability. The analytical performance and application feasibility of the sensor was measured by severaldifferent electrochemical techniques such as cyclic voltammetric (CV), differential pulse voltammetric(DPV), electrochemical impedance spectroscopy (EIS). The sensor response indicates a linear range from5.0 fg/mL to 1.0 pg/mL with a detection limit of 1.67 fg/mL. Moreover, the application of the proposedmethod to determination of HCV core antigen in human serum sample has been successfully evaluated;satisfactory results were obtained, the results show great potential of the fabricated sensor for real sampleanalysis.
Synthesis, characterization and spectroscopic studies of nickel (II) complexes with some tridentate ONN donor Schiff bases and their electrocatalytic application for oxidation of methanol
Abstract
Synthesis, characterization and spectroscopic studies of nickel (II) complexes with some tridentate ONN donor Schiff bases and their electrocatalytic application for oxidation of methanol
Some tridentate Schiff base ligands (L1–L5) and their nickel complexes [NiL (PR3)]; (where L1 = N-salicyliden- 2,3-diamino-cis-2-butenedinitrile, L2 = 3-methoxy-N-salicyliden-2,3-diamino-cis-2-butenedinitrile, L3 = 5- Bromo-N-salicyliden-2,3-diamino-cis-2-butenedinitrile, L4 = 5-nitro - N-salicyliden-2,3-diamino-cis-2- butenedinitrile, L5=5-methoxy-N-salicyliden-2,3-diamino-cis-2-butenedinitrile)were synthesized and characterized by different spectroscopic techniques. The geometry of [NiL2 (PPh3)] and [NiL5 (PPh3)] were determined by X-ray crystallography. Both of the structures show distorted square planer geometry. In addition, the optimized geometries of the ligands and complexes along with their IR spectra were calculated by the density functional theory (DFT). The time-dependent-density functional theory (TD-DFT) was employed to calculate the absorption spectra of the structures. The calculated IR and absorption spectra were compared with the corresponding experimental spectra to confirm the experimental results. The calculated IR and absorption spectra were assigned based on the theoretical calculations. Also, the nickel complexeswere electrochemically dispersed onto multi-wall carbon nanotubes (MWCNTs) and their electrocatalytic activity for the oxidation of methanol have been studied by cyclic voltammetry. Based on the results, the nickel complexeswere found to be active catalysts in the electro-oxidation of methanol.
Encapsulated phosphomolybdic acid in TMU-16 metal organic framework: Study the catalytic activity and structural stability dependent on synthetic solvent
Abstract
Encapsulated phosphomolybdic acid in TMU-16 metal organic framework: Study the catalytic activity and structural stability dependent on synthetic solvent
Encapsulated phosphomolybdic acid in the TMU-16,HPMA@TMU-16, at three different solventswas synthesized and characterized. For characterization studies XRD, ICP, TGA, CHNS, BET, SEM-EDS and TEMmethodswere used. Evidences such as loss of specific surface area, EDS elemental mapping and similar XRD patterns confirmed that HPMA to be import in the TMU-16 pores. A catalytic activity of samples was performed in the oxidation of sulfides and optimum conditions were studied in the dibenzyle sulfide oxidation reactions. Obtained results including short reaction times, selectivity to sulfoxide and reusability exhibited high performance of HPMA@TMU-16 as heterogeneous catalyst. Increasing number of recovered cycles with shorter reaction times revealed effect of polarity of synthetic solvent on the catalytic activity and structural stability.
Preparation an electrochemical sensor for detection of manganese (II) ions using glassy carbon electrode modified with multi walled carbon nanotubechitosan- ionic liquid nanocomposite decorated with ion imprinted polymer
Abstract
Preparation an electrochemical sensor for detection of manganese (II) ions using glassy carbon electrode modified with multi walled carbon nanotubechitosan- ionic liquid nanocomposite decorated with ion imprinted polymer
An electrochemical sensor for the determination of manganese (II) ion with high selectivity was developed by using modified glassy carbon electrode with a nanocomposite film containing immobilized Mn(II)-IIP particles abbreviated as Mn(II)-IIP/MWCNT/Chit/IL/GCE. The manipulation of IIP increases the selectivity of the sensor and the presence of MWCNT/Chit/IL provides significant enhancement of the electron transfer rate during redox reactions. The Mn(II)IIP-NPs were obtained by thermal polymerization of Methacrylic acid (the monomer), ethylene glycol dimethacrylate (cross-linker), 2,2′-azobisisobutyronitrile (chemical initiator), 1-(2-Pyridylazo)- 2-naphthol (manganese-binding ligand), and manganese ions (template ion) in ethanol. The response of the constructed sensor was linear in the range of 2.0 to 9.0 μM with a detection limit of 0.15 μM and much higher sensitivity (130.5 nA μM−1 cm−2). The important parameters such as IIP amount, preconcentration potential and accumulation time were optimized to be 1.0 mg, −1.4 V and 120 s, respectively. The interference of different ionic species with the response of the sensor was also studied. The proposed sensor provides the important advantages of relative high sensitivity, excellent selectivity and operation convenience as well as low detection limit.
A glassy carbon immunoelectrode modified with vanadium oxide nanobelts for ultrasensitive voltammetric determination of the core antigen of hepatitis C virus
Abstract
A glassy carbon immunoelectrode modified with vanadium oxide nanobelts for ultrasensitive voltammetric determination of the core antigen of hepatitis C virus
The authors describe a voltammetric immunoassay for the hepatitis C virus core antigen. It is based on the use of vanadium oxide nanobelts that were used to modify a glassy carbon electrode (GCE). The nanobelts have a large specific surface area that can be heavily loaded with antibody against the hepatitis C virus core antigen. Following blocking with BSA and by using riboflavin as an electrochemical probe, the immuno GCE (best operated at a working voltage of −0.45 V vs. Ag/AgCl) has a linear response that covers the 10 fg·mL−1 to 100 ng·mL−1 core antigen concentration range and a limit of detection as low as 1.3 fg mL−1. Compared to the other redox probes, riboflavin is superior because it is oxidized in the negative potential range, where the number of interfering species for riboflavin is small. The method was successfully applied to the determination of hepatitis C virus core antigen in spiked serum. In our perception, the use of a V2O5 nanobelt film as a support for bioreceptors has a wide scope in that in that it may be extended to immunoassays for various other diagnostically significant analytes.
On-line flow injection solid phase extraction using imprinted polymeric nanobeads for the preconcentration and determination of mercury ions
Abstract
On-line flow injection solid phase extraction using imprinted polymeric nanobeads for the preconcentration and determination of mercury ions
This work reports a new analytical method for the preconcentration and determination of Hg2+ ions based on flow injection technique coupled with a solid phase extraction process. Hg2+ ion imprinted polymeric (IIP) nanomaterials were prepared by using the bulk polymerization procedure, and then applied as an efficient solid phase extractor for selective separation of Hg2+ ions. The prepared sorbent was characterized using FT-IR spectroscopy, scanning electron microscopy (SEM), various thermal analysis methods, and Brunauer, Emmett, and Teller adsorption isotherm analysis (BET). According to the results, surface area, pore volume and average pore diameter of the prepared Hg-IIP were found to be 3.05 102 m2 g1, 1.07 cm3 g1 and 15.33 nm, respectively. In the sorption studies, after preconcentration and loading of Hg2+ ions on the IIP sorbent, its mercury content was eluted by suitable solution and then determined photometrically, by a designed on-line recording process coupled with a flow injection procedure. The influence of the mercury concentration, preconcentration and elution times, nature, volume, and concentration of the eluent, pH, and flow rate of the solution and eluent on the polymer affinity has been investigated. Bound Hg2+ ions can be eluted with 5 mL of nitric acid 1.0 mol L1 and then treated with diphenylthiocarbazone, finally quantified photometrically at 485 nm. The relative standard deviation and detection limit (3r) of the method for eight replicates at optimum pH, were evaluated as 4.2% and 0.036 ng mL1, respectively. The IIP sorbent show an excellent selectivity for Hg2+ ion over other metal ions and was successfully applied to the selective extraction and determination of Hg2+ ion in water and human hair samples.
Impedimetric detection of trinitrotoluene by using a glassy carbon electrode modified with a gold nanoparticle@fullerene composite and an aptamer-imprinted polydopamine
Abstract
Impedimetric detection of trinitrotoluene by using a glassy carbon electrode modified with a gold nanoparticle@fullerene composite and an aptamer-imprinted polydopamine
This study introduces a method based on a combination of aptasensing and molecular imprinting for highly sensitive detection of 2,4,6-trinitrotoluene (TNT). An amino-aptamer with inherent affinity for TNT was mixed with TNT prior to covalent attachement onto a glassy carbon electrode surface which was modified with a nanocomposite of the type gold nanoparticle@fullerene (AuNP@C60). Electropolymerization of dopamine around the aptamer/TNT complex entraps the complex and retains the aptamer. After removal of TNT, it is assumed that the MIP cavity acts synergistically with the embedded aptamer to form a nanohybrid receptor (aptamer-molecular imprinting polymer). This results in recognition properties superior to that of aptamer alone. Benefiting from the double specific molecular recognition property of molecular imprinting polymers and aptamers along with the in situ generation of AuNP onto the surface of the modified GCE leads to superb sensing properties. Properties such as lower limit of detection (3.5 attomolar) and wider linear concentration range of TNT (0.01 femtomolar to 1.5 μmol L−1) are distinctly better than other reported methods. In our perception, this strategy may be extended to various diagnostically relevent proteins using not only aptamers but also other affinity molecules such as affimers, antibody and peptide fragments.
Fabrication of an Electrochemical Immunosensor for Determination of Human Chorionic Gonadotropin Based on PtNPs/Cysteamine/AgNPs as an Efficient Interface
Abstract
Fabrication of an Electrochemical Immunosensor for Determination of Human Chorionic Gonadotropin Based on PtNPs/Cysteamine/AgNPs as an Efficient Interface
An ultrasensitive electrochemical immunosensor for the detection of tumor marker human chorionic gonadotropin (hCG) was developed with a limit of detection as low as 2 pg ml-1 in phosphate buffer. The platinum nanoparticles (PtNPs) were electrodeposited to modify the gold surface and to increase enlarging the electrochemically active sites, resulting in the facilitation of electron exchange. Cysteamine (Cys) self-assembled monolayer was chemisorbed spontaneously on Pt substrates via the Pt-S bond and the amine groups array exposed on the electrode surface was used to anchor AgNPs through electrostatic interaction. AgNPs increased the immobilized amount of antibodies on the electrode to enhance the sensitivity of the sensor. Under optimal experimental parameters, differential pulse voltammetry (DPV) signal changes of the [Fe(CN)6]3-/4- are used to detect hCG with two broad linear ranges: 0.007-1.11 and 1.11-68 ng ml-1. The reported strategy has provided a promising platform for highly sensitive and selective detection of hCG. Finally, the proposed immunosensor is successfully used in detecting hCG in human serum samples.
Using Au@nano-C60 nanocomposite as an enhanced sensing platform in modeling a TNT aptasensor
Abstract
Using Au@nano-C60 nanocomposite as an enhanced sensing platform in modeling a TNT aptasensor
Based on the unique characteristics of the combination of fullerene and gold nanoparticles, we successfully designed a new and facile nanocomposite (Au@nano-C60) to fabricate an aptasensor for the ultra-sensitive and selective detection of TNT. The gold nanoparticles decorated fullerene onto a glassy carbon electrode was prepared using an electrochemical method by the in situ generation of Au nanoparticles onto the surface of the glassy carbon electrode modified with activated fullerene. Successively, the NH2-Apt as a receptor molecule of 2,4,6-Trinitrotoluen was covalently attached onto the modified electrode surface with the resultant nanocomposite. With the addition of the target onto the aptasensor surface and the formation of target/Apt complex, a linear response was obtained from 0.50 fM to 5 mM as well as a limit of detection down to 0.17 fM. The proposed aptasensor shows a wider linear response range and lower limit of detection for the specific detection of 2,4,6-Trinitrotoluen. This newly developed strategy will pave the way to partly meet the requirements in the field of homeland security and public safety.
Flame Atomic Absorption Spectrometric Determination of Cadmium in Vegetable and Water Samples After Preconcentration Using Magnetic Solid-Phase Extraction
Abstract
Flame Atomic Absorption Spectrometric Determination of Cadmium in Vegetable and Water Samples After Preconcentration Using Magnetic Solid-Phase Extraction
Accurate and reliable determination of cadmium (Cd) in vegetables is often difficult due to low concentrations and matrix effects. Magnetic solid-phase extraction (MSPE) was developed for preconcentration and determination of trace amounts of Cd in vegetables and water samples prior to flame atomic absorption spectrometry (FAAS) analysis. Cobalt magnetic nanoparticles were synthesized and modified by sodium dodecyl sulfate (SDS) and 2-(5-bromo-2- pyridylazo)-5-diethyl aminophenol ligand (5-Br-PADAP) through a chemical precipitation method so that the nanoparticles (NPs) could be used as a new sorbent. The NPs bearing the Cd ions were easily separated from the aqueous solution by applying an external magnetic field and the complexed metals were desorbed using dilute HNO3. Extraction conditions including pH, amount of sorbent, contact time, desorption solvent, breakthrough volume, and sorption capacity were optimized. Under optimal conditions, the calibration curve was linear from 1.0–500 ng·mL−1 of Cd, R2 = 0.997. The detection limit was 0.6 ng·mL−1 in the original solution (3 Sb·m−1) and the relative standard deviation for eight replicates determination of 0.1 μg·mL−1 Cd was ±2.2%. Cadmium is easily aggregated in edible parts of leafy vegetables. Heavy metals analysis of vegetables is essential for protection of humanhealth and to comply with regulatory controls.
Determination of Two Sulfonylurea Herbicides Residues in Soil Environment Using HPLC and Phytotoxicity of These Herbicides by Lentil Bioassay
Abstract
Determination of Two Sulfonylurea Herbicides Residues in Soil Environment Using HPLC and Phytotoxicity of These Herbicides by Lentil Bioassay
A HPLC-UV detection system was used for determination of sulfosulfuron and tribenuron methyl residues from soils. The soils were fortified with sulfosulfuron and tribenuron methyl at rates of 26 and 15 g a.i. ha− 1 respectively and samples were taken randomly on 0 (2 h), 1, 2, 4, 10, 20, 40, 60, 90 and 120 days after treatment. The final extracts were prepared for analysis by HPLC. The results showed that degradation of both herbicides in the silty loam soil was faster than sandy loam soil. Half-life of sulfosulfuron was ranged from 5.37 to 10.82 days however this value for tribenuron methyl was ranged from 3.23 to 5.72 days on different soils. The residue of both herbicides at 120 days after application in wheat field had no toxicitic effect on lentil. It was concluded that HPLC analysis procedure was an appropriate method for determination of these herbicides from soils.
TiO2 nanoparticles doped with Celestine Blue as a label in a sandwich immunoassay for the hepatitis C virus core antigen using a screen printed electrode
Abstract
TiO2 nanoparticles doped with Celestine Blue as a label in a sandwich immunoassay for the hepatitis C virus core antigen using a screen printed electrode
The authors describe an electrochemical immunoassay for the core antigen of hepatitis C virus (HCV). The method is based on the use of a screen-printed carbon electrode (SPCE) that was modified with a Nafion@TiO2 nanocomposite and loaded with secondary antibody (Ab2) to entrap Celestine Blue (CB). The material has architecture of the type CB/Ab2/Nafion@TiO2. A nanocomposite consisting of graphene, ionic liquid and fullerene was deposited on the SPCE first, and rhodium nanoparticles (RhNPs) were then deposited on the surface of modified electrode in order to immobilize primary antibody (Ab1). The antigen and CB/Ab2/Nafion@TiO2 were conjugated one by one to form a sandwich-type immunocomplex. The signal was obtained by differential pulse voltammetry whose intensity is related to the concentration of the antigen. The assay, if operated at a working voltage of typically 0.35 V (vs. Ag/AgCl) has a response that is linear in the 0.1 to 250 pg⋅mL−1 HCV core antigen concentration range, and the limit of detection is as low as 25 fg⋅mL−1. The assay was applied to the determination of the HCV core antigen in spiked human serum samples. In our perception, the method represents a promising platform for the detection of various antigens if appropriate antibodies are available
Synthesis and photoluminescence properties of Ru-doped ZnS quantum dots
Abstract
Synthesis and photoluminescence properties of Ru-doped ZnS quantum dots
In thepresentwork,thefeasibilitystudyofgrowthdopingstrategyfordirectpreparationofRu-doped ZnS quantumdots(QDs)inaqueoussolutionisinvestigatedbyX-raypowderdiffraction(XRD),trans- mission electronmicroscopy(TEM),UV–vis absorption,andphotoluminescence(PL)emissionspectro- scopies. StructuralinvestigationsindicatedthattheRu-dopedZnSQDswereabout3nminsize,showing size-dependent opticalpropertiesofthepreparedQDs.Specifically,threedifferentpeaksareobservedin photoluminescencespectraofRu-dopedZnSspecimens;averyweakexcitonicemissionatabout 350 nm,thebluetrap-relatedemissionaround420nm,andastrongcyandopant-relatedemissionat about 450nm.VariousparameterssuchassolutionpH,refluxing temperatureandprecursorsmolar ratios wereobservedtohavesignificant effectsonemissionpropertiesoftheas-preparedQDs.Byop- timization ofeachparameter,thebestresultforpreparationoftheRu-dopedQDswasdeterminedtobe; solution pH¼11,refluxing temperatureof100 °C andtheZn:ME:Ru:Smolarratioof1:50:0.01:0.5. Considering thesimplicity,fastness,andtheirnotablechemicalandopticalstabilities,thepresentQDs can beacandidateforvarietyofapplicationsinbiotechnologyandoptoelectronicdevices.
Ultra-sensitive detection of ibuprofen (IBP) by electrochemical aptasensor using the dendrimer-quantumdot (Den-QD) bioconjugate as an immobilization platform with special features
Abstract
Ultra-sensitive detection of ibuprofen (IBP) by electrochemical aptasensor using the dendrimer-quantumdot (Den-QD) bioconjugate as an immobilization platform with special features
This study describes a high-performance electrochemical aptasensorwhich isemployed to detect Ibuprofen (IBP) as a painkiller drug by using a novel platformas an integrated sensing interface. In order to make the aptasensor, the Den-QD bioconjugate was immobilized on the surface of a GC electrode and followed the Apt was incubated on this surface. The incubation of the IBP on the aptasensor surface and the formation of the Apt/IBP complex, led to a hindered electron transfer reaction on the sensing surface, which decreased the peak current of the redox probe. Under the optimum condition, the assay had two dynamic ranges with a detection limit down to 333 fM. The developed aptasensor reliably detects IBP in a real sample. Our results demonstrated that the proposed strategy has many advantages and the Den-QD bioconjugate may become a promising nanocomposite for the electrochemical sensing applications.
Removal of cadmium ions from aqueous solutions using TMU-16-NH2 metal organic framework
Abstract
Removal of cadmium ions from aqueous solutions using TMU-16-NH2 metal organic framework
In this research, removal of cadmium from aqueous samples by TMU-16-NH2 metal–organic framework was investigated. In a batch process method, the effect of pH, initial concentration, contact time, temperature and sorbent weight on sorption process was studied. Equilibrium isotherms were fitted by Langmuir and Freundlich equations. The maximum adsorption capacity of Cd(II) was determined 126.6 mg g−1 . The metal–organic framework was successfully applied to the quick extraction of trace amounts of Cd(II) ions in water samples. The maximum removal percentage was obtained 98.91 at pH 6.0 and 30 min contact time. The Gibbs free energy (G0 ), the enthalpy (H0), and the entropy (S0) were also calculated from thermodynamic studies. The positive values of H0, S0 and the negative value of G0, confirmed the endothermic nature, randomness and spontaneity of adsorption process.
Immunoassay for Human Chorionic Gonadotropin Based on Glassy Carbon Electrode Modified with an Epitaxial Nanocomposite
Abstract
Immunoassay for Human Chorionic Gonadotropin Based on Glassy Carbon Electrode Modified with an Epitaxial Nanocomposite
A highly sensitive electrochemical immunosensor was developed to detect hCG based on immobilization of hCG-antibody (anti-hCG) onto robust nanocomposite containing Gr, Chit, 1-methyl-3-octyl imidazolium tetra fluoro borate ionic liquid (IL) (Gr-IL-Chit). AuNPs were used to immobilize hCG antibody on the modified electrode. The amine groups of the antibody are covalently attached to AuNPs/Gr- IL-Chit nanocomposite. CV, EIS and SEM were employed to characterize the assembly process and the performance of the immunosensor. DPV and EIS studies demonstrated that the formation of antibody-antigen complexes decreased peak current and increased Rct of [Fe(CN)6]3−/4− redox pair at the AuNPs/Gr-IL-Chit/GCE. The optimization of the pH of supporting electrolyte and the incubation time were studied in details. Because of the synergistic effect of IL, Chit and Gr and the unique properties of AuNPs, the obtained immunosensor exhibited a wide linear response to hCG in two ranges from 0.005-1.484 and 1.484-411.28 (mIU ml-1). A relatively low detection limit of 0.0016 mIU ml-1 (S/N = 3) was calculated from DPV. Satisfactory results were obtained for determination of hCG in human serum samples.
Application of graphene quantum dots as green homogenous nanophotocatalyst in the visible-light-driven photolytic process
Abstract
Application of graphene quantum dots as green homogenous nanophotocatalyst in the visible-light-driven photolytic process
Environmental pollution has become one of the greatest problems worldwide, and photocatalysts have attracted a great deal of attention as one solution to this problem. In the present study, we report a novel environmentally friendly property of graphene quantum dots (GQDs) as efficient nano-materials for the degradation of organic pollutant dyes based on the photocatalytic behavior of GQDs under visible-light irradiation. GQD samples were derived from citric acid by a pyrolysis procedure. The synthesized GQDs were characterized by various techniques including transmission electron microscopy, UV–Vis absorption, Raman spectroscopy, fluorescence spectroscopy, and zeta potential measurements. The photocatalytic degradation of Celestine Blue (CB) was studied using GQDs under visible light irradiation. The effect of pH value, contacting time, dosage of GQDs, and initial dye concentration on the degradation kinetics of CB was systematically investigated. MS analyses were conducted to determine the degradation products evolving during the photocatalytic degradation. The possible mechanisms of degradation of CB based on GQDs under visible light are discussed as well.
Amperometric NADH sensor based on a carbon ceramic electrode modified with the natural carotenoid crocin and multi-walled carbon nanotubes
Abstract
Amperometric NADH sensor based on a carbon ceramic electrode modified with the natural carotenoid crocin and multi-walled carbon nanotubes
A carbon ceramic electrode (CCE) was fabricated from a composite consisting of sol-gel, ceramic graphite, multi-walled carbon nanotubes and the natural carotenoid crocin. The resulting sensor is shown to allow for the determination of NADH at a rather low working potential of 0.22 V (vs. Ag/AgCl). The heterogeneous electron transfer rate constant (ks) and the surface coverage of the modified electrode are 16.8 s−1 and 22 pmol·cm−2, respectively. The sensor shows excellent and linear response in solutions of pH 7.0 over the 0.5 to 100 μMNADH concentration range, a 0.1 μMdetection limit, and a sensitivity of 251.3 nA·μM−1·cm−2.
Development of novel electrochemical sensor on the base of molecular imprinted polymer decorated on SiC nanoparticles modified glassy carbon electrode for selective determination of loratadine
Abstract
Development of novel electrochemical sensor on the base of molecular imprinted polymer decorated on SiC nanoparticles modified glassy carbon electrode for selective determination of loratadine
A novel and selective electrochemical sensor was successfully developed for the determination of loratadine by drop coating of synthesized loratadine molecularly imprinted polymers on the surface of glassy carbon electrode modified with silicon carbide nanoparticles. The performance of the constructed sensor was evaluated by cyclic voltammetry, scanning electron microscopy, and electrochemical impedance spectroscopy techniques. Under optimized conditions, the resulting calibration curve exhibited a linear response within a concentration range of 1–33 μM with a low detection limit (S/N= 3) of 0.15 μM. Finally, the proposed method was successfully applied as a selective, stabile, sensitive, simple, reproducibility electrochemical sensor with good repeatability for the determination of loratadine in real samples and satisfactory results were obtained
Using silver nanoparticle and thiol graphene quantum dots nanocomposite as a substratum to load antibody for detection of hepatitis C virus core antigen: Electrochemical oxidation of riboflavin was used as redox probe
Abstract
Using silver nanoparticle and thiol graphene quantum dots nanocomposite as a substratum to load antibody for detection of hepatitis C virus core antigen: Electrochemical oxidation of riboflavin was used as redox probe
In this study a facile green approach to employ silver nanoparticle (AgNPs) and thiol graphene quantum dots (GQD-SH) as the nanomaterial for ultrasensitive and selective detection of hepatitis C virus core antigen (HCV) have been investigated. AgNPs/GQD-SH was utilized as a substratum to load antibody for detection of hepatitis C virus core antigen. AgNPs have been immobilized on SH groups of GQDs via bonding formation of Ag-S and anti-HCV have been loaded on the electrode surface via the interaction between –NH2 group of antibody and AgNPs. Using the proposed nanocomposite provides a specific platform with increased surface which is capable of loading more antibodies to entrap the antigen. The decreasing of the electrochemical signal can be achieved after the specific recognition between antibodies and antigens. Riboflavin was used as a biological molecule with inherent properties, for the first time, as the redox probe in the development of HCV core antigen electrochemical immunosensor. Compared to the other redox probes, riboflavin is superior in its oxidization in negative potential range, where the number of interfering species for riboflavin is much fewer. The proposed immunosensor showed wide linear range from 0.05 pg mL−1 to 60 ng mL−1 with limit of detection of 3 fg mL−1. This novel immunosensor was used to analyze the serum sample. The immunosensor provides a convenient, low-cost and simple method for HCV core antigen detection and proposes new horizons for quantitative detection of antigen in the clinical diagnosis.
Synthesis, spectroscopy, electrochemistry and structural determination of asymmetric cobalt(III) Schiff base complexes
Abstract
Synthesis, spectroscopy, electrochemistry and structural determination of asymmetric cobalt(III) Schiff base complexes
The [CoL(PR3)(CH3OH)]ClO4 (where L = MeSalophen, 5-NO2MeSalophen, 5-BrMeSalophen, 5-MeOMeSalophen, 4-MeOMeSalophen, 3-MeOMeSalophen and R=Ph or Bu) complexes were synthesized and also characterized by FTIR, UV–Vis, 1H NMR and 13C NMR spectroscopies. The absorptions between 550 and 750 nm for the complexes are attributed to d–d transitions. Electrochemical properties of the complexes were examined by means of cyclic voltammetry. The anodic peak potentials were more positive in the following trend NO2 > Br > H > MeO and are in accordance with electronic effects of the substituents. The crystal structure of [Co(5-NO2MeSalophen)(PBu3)(CH3OH)]ClO4 and [Co(5- BrMeSalophen)(PPh3)(CH3OH)]ClO4 was determined by single-crystal X-ray diffraction. They showed six-coordinated pseudo-octahedral geometries in which equatorial planes are formed by the O(1), O(2), N(1) and N(2) atoms of the Schiff base and the axial positions were occupied by PR3 and methanol.
Designing an ultra-sensitive aptasensor based on an AgNPs/thiol-GQD nanocomposite for TNT detection at femtomolar levels using the electrochemical oxidation of Rutin as a redox probe
Abstract
Designing an ultra-sensitive aptasensor based on an AgNPs/thiol-GQD nanocomposite for TNT detection at femtomolar levels using the electrochemical oxidation of Rutin as a redox probe
In this paper, for the first time a highly sensitive and low-cost electrochemical aptasensor was fabricated based on a silver nanoparticles/thiol functionalized graphene quantum dot (AgNPs/thiol-GQD) nanocomposite for the measurement of 2,4,6-Trinitrotoluen (TNT) as a nitroaromatic explosive. For the first time Rutin (RU) as a biological molecule with inherent properties was used as the redox probe in the development of the TNT aptasensor was used. The system was based on a TNT-binding aptamer which is covalently attached onto the surface of a glassy carbon electrode (GCE) modified with the nanocomposite for the formation of a sensing layer and improving the performance of the aptasensor. Using the proposed nanocomposite provides a specific platform with increased surface area which is capable of loading more Aptamer (Ap) molecules as a receptor element of TNT on the electrode surface. So, TNT molecules is in an upward position to be measured and the obtained results indicate that the aptasensor exhibits two wide linear ranges and an unprecedented LOD compared with previously reported analytical methods for TNT detection. Applicability of the developed aptasensor to easily detect TNT in real samples was evaluated. It seems that the proposed strategy can be expanded to other nanoparticles and is expected to have promising implications in the design of electrochemical sensors or biosensors for the detection of various targets.
Surface-Renewable AgNPs/CNT/rGO Nanocomposites as Bifunctional Impedimetric Sensors
Abstract
Surface-Renewable AgNPs/CNT/rGO Nanocomposites as Bifunctional Impedimetric Sensors
In this study, glassy carbon electrode modified by silver nanoparticles/carbon nanotube/reduced graphene oxide (AgNPs/CNT/rGO) composite has been utilized as a platform to immobilize cis-dioxomolybdenum (VI)–salicylaldehydehistidine (MoO2/Sal-His). The modified electrode shows two reversible redox couples for MoO2/Sal-His. Electrocatalytic oxidation of cysteine (CySH) and electrocatalytic reduction of iodate on the surface of the modified electrode were investigated with cyclic voltammetry and electrochemical impedance spectroscopy methods. The presence of MoO2/Sal- His on AgNPs/CNT/rGO shifted the catalytic current of iodate reduction to a more positive potential and the catalytic current of cysteine oxidation to a more negative potential. The change of interfacial charge transfer resistance (Rct) recorded by the modified electrode was monitored for sensitive quantitative detection of CySH and iodate. Moreover, the sensor has a good stability, and it can be renewed easily and repeatedly through a mechanical or electrochemical process
A novel impedimetric aptasensor, based on functionalized carbon nanotubes and prussian blue as labels
Abstract
A novel impedimetric aptasensor, based on functionalized carbon nanotubes and prussian blue as labels
A simple and feasible electrochemical sensing protocol was developed for the detection of bisphenol A (BPA) by employing the gold nanoparticles (AuNPs), prussian blue (PB) and functionalized carbon nanotubes (AuNPs/PB/CNTs-COOH). An aminated complementary DNA as a capture probe and specific aptamer against BPA as a detection probe was immobilized on the surface of a modified glassy carbon (GC) electrode via the formation of covalent amide bond and hybridization, respectively. The proposed nanoaptasensor combined the advantages of the in situ formation of PB as a label, the deposition of neatly arranged AuNPs, and the covalent attachment of the capture probe to the surface of the modified electrode. Upon addition of target BPA, the analyte reacted with the aptamer and caused the steric/ conformational restrictions on the sensing interface. The formation of BPAeaptamer complex at the electrode surface retarded the interfacial electron transfer reaction of the PB as a probe. Sensitive quantitative detection of BPA was carried out based on the variation of electron transfer resistance which relevant to the formation of BPAe aptamer complex at the modified electrode surface. Under the optimized conditions, the proposed aptasensor exhibited a high sensitivity, wide linearity to BPA and low detection limit. This aptasensor also displayed a satisfying electrochemical performance with good stability, selectivity and reproducibility.
Evaluation of four different crops’ sensitivity to sulfosulfuron and tribenuron methyl soil residues
Abstract
Evaluation of four different crops’ sensitivity to sulfosulfuron and tribenuron methyl soil residues
On the basis of greenhouse bioassays, the sensitivities of root and shoot biomass of barley (Hordeum vulgare L.), corn (Zea mays L.), oilseed rape (Brassica napus L.) and sugar beet (Beta vulgaris L.) to soil-incorporated sulfosulfuron and tribenuron methyl were assessed. Shoot and root biomass production was measured 30 days after emergence. Plant responses, including roots and shoots dry weight per pot, were described by a three parameter loglogistic regression model as a function of sulfosulfuron or tribenuron methyl doses and the relative sensitivities were calculated at the various ED-levels with their associated 95% confidence intervals. The most precise ED-levels were that at ED50 and sensitivity rank was oilseed rape, sugar beet, corn and barley, whatever the chosen response level and herbicide. We calculated relative sensitivities at ED10, ED50 and ED90 for the species of barley, the most tolerant crop, as reference. Comparison of relative sensitivity of crops to both herbicides showed that the sensitivity of these crops was much larger for tribenuron methyl than for sulfosulfuron. Oilseed rape was the most sensitive species (ED50 = 0.202 and 0.179 μg kg−1 soil for root dry weight (RDW) response to sulfosulfuron and tribenuron methyl, respectively) while barley was the most tolerant one (ED50 = 1.008 and 3.68 μg kg−1soil for RDW response to sulfosulfuron and tribenuron methyl, respectively). Sugar beet and corn had intermediate sensitivity. Also, we demonstrated how important it is to show the confidence intervals of relative sensitivities. In several instances the relative sensitivities, even numerically large, were not significantly different from 1.00. We demonstrate that classifying biotypes as resistant to a herbicide requires the threshold of resistance/susceptible (R/S) of 4.00 only be accepted if confidence intervals do not cover 1.00.
Anionic dyes removal from aqueous solution using TMU-16 and TMU-16-NH 2 as isoreticular nanoporous metal organic frameworks
Abstract
Anionic dyes removal from aqueous solution using TMU-16 and TMU-16-NH 2 as isoreticular nanoporous metal organic frameworks
The adsorptive removal of anionic dyes were investigated over two isoreticular nanoporous Zn(II)-MOFs known as TMU-16 and TMU-16-NH 2 in view of the influence of an amine group on the adsorption capac- ity. Adsorption isotherms, thermodynamics and kinetics parameters of the sorbents were studied and also effective factors on dye adsorption have been optimized. Thermodynamic and kinetic results revealed ad- sorption over two MOFs is spontaneous and pseudo-second order, as well as TMU-16-NH 2 showed higher removal yield to TMU-16 because of forming hydrogen bonding between dyes and amine groups. These MOFs showed great adsorption uptakes for anionic dyes than other porous materials that reported pre- viously. Adsorption mechanism could be explained by electrostatic and hydrogen bonding interactions. Importantly TMU-16 and TMU-16-NH 2 due to high adsorption capacity and stability of structures could be employed as excellent sorbents to remove harmful dyes in contaminated water
A simple and label-free aptasensor based on amino group-functionalized gold nanocomposites-Prussian blue/carbon nanotubes as labels for signal amplification
Abstract
A simple and label-free aptasensor based on amino group-functionalized gold nanocomposites-Prussian blue/carbon nanotubes as labels for signal amplification
Herein, a novel label-free electrochemical aptasensor based on gold nanoparticles/Prussian blue/carbon nanotubes (AuNPs/PB/CNTs) for dopamine (DA) determination was reported. A special AuNPs/PB/CNTs nanocomposite which integrated the individual properties of each nanomaterial was utilized to improve the conductivity and performance characteristics of the biosensor as well as to increase the loading amount of aptamer. Chitosan was coated onto nanocomposite and provided a biocompatible interface with abundant- NH2 groups for the immobilization of DA-specific aptamer. Abundant-NH2 groups in nanocomposite made this platform as significant transduction by allowing phosphoramidate bonds formed between the amino group of chitosan and phosphate group of the aptamer at 5′end. To translate the binding events between aptamer and DA into the measurable electrochemical signal, the PB as signal probe was in situ introduced on the electrode surface, exhibiting well-defined peaks with good stability and reproducibility. The designed immobilized DA– aptamer resulted in the formation of long tunnels on modified electrode surface, while aptamer acted as gate of the tunnels. The aptamer gates were closed due to change in conformation of aptamer upon target (DA) binding, retarding the interfacial electron transfer reaction of the probe, resulting in the decrease of the electrochemical signal. Under optimized conditions, the proposed aptasensor showed good detection range from 0.5 to 50 nM with unprecedented detection limit of 200 pM. This aptasensor also exhibited good stability and high selectivity for DA detection without an interfering effect of some other compounds.
Design of folding-based impedimetric aptasensor for determination of the nonsteroidal anti-inflammatory drug
Abstract
Design of folding-based impedimetric aptasensor for determination of the nonsteroidal anti-inflammatory drug
In this work, a novel sensing nanocomposite with highly dispersed platinum nanoparticles (PtNPs) on carbon nanotubes (CNTs) functionalized with polyethyleneimine (PEI) has been developed as a platform for immobilization of diclofenac (DIF) aptamer. PtNPs/PEI/CNTs nanocomposite provided abundant eNH2 groups for the immobilization of DIF-specific aptamer. Attachment of DIFeaptamer at the surface of modified electrode was performed through the formation of phosphoramidate bonds between the amino group of PEI and the phosphate group of the aptamer at the 50 end. Nickel hexacyanoferrate (NiHCF) as signal probe was electrodeposited at the surface of nanocomposite by a simple electrodeposition method including two consecutive procedures. Under optimal conditions, DIF was detected by impedance spectroscopy (EIS) quantitatively. By adding DIF as the target at the surface of modified electrode, the aptamer specifically binds to DIF and its end folds into a DIF-binding junction, which leads to retarding the interfacial electron transfer of the probe at the surface of modified electrode. Sensitive quantitative detection of DIF was carried out by monitoring the increase of charge transfer resistance (Rct) by increasing the DIF concentration. The proposed aptasensor showed a good detection range from 10 to 200 nM with an unprecedented detection limit of 2.7 nM.
Design of ultrasensitive bisphenol Aeaptamer based on platinum nanoparticles loading to polyethyleneimine-functionalized carbon nanotubes
Abstract
Design of ultrasensitive bisphenol Aeaptamer based on platinum nanoparticles loading to polyethyleneimine-functionalized carbon nanotubes
Here, a highly sensitive electrochemical aptasensor based on a novel signal amplification strategy for the determination of bisphenol A (BPA) was developed. Construction of the aptasensor began with the deposition of highly dispersed platinum nanoparticles (PtNPs)/acid-oxidized carbon nanotubes (CNTs eCOOH) functionalized with polyethyleneimine (PEI) at the surface of glassy carbon (PtNPs/PEI/CNTs eCOOH/GC) electrode. After immobilizing the amine-capped capture probe (ssDNA1) through the covalent amide bonds formed by the carboxyl groups on the nanotubes and the amino groups on the oligonucleotides, we employed a designed complementary BPAeaptamer (ssDNA2) as a detection probe to hybridize with the ssDNA1. By adding BPA as a target, the aptamer specifically bound to BPA and its end folded into a BPA-binding junction. Because of steric/conformational restrictions caused by aptamereBPA complex formation at the surface of modified electrode, the interfacial electron transfer of [Fe(CN)6]3/4 as a probe was blocked. Sensitive quantitative detection of BPA was carried out by monitoring the decrease of differential pulse voltammetric responses of [Fe(CN)6]3/4 peak current with increasing BPA concentrations. The newly developed aptasensor embraced a number of attractive features such as ease of fabrication, low detection limit, excellent selectivity, good stability and a wide linear range with respect to BPA.
Fabrication of an electrochemical nanoaptasensor based on AuNPs for ultrasensitive determination of cocaine in serum sample
Abstract
Fabrication of an electrochemical nanoaptasensor based on AuNPs for ultrasensitive determination of cocaine in serum sample
Hereinwedescribe an ultrasensitive electrochemical nanoaptasensor for the detection of one of themost dangerous narcotic drugs available, cocaine. The nanoaptasensor was constructed by the covalent attachment of a 5′- NH2-3′-gold nanoparticles terminated aptamer on the surface of a glassy carbon electrode which was deposited with gold nanoparticles (AuNPs/GCE). It is worth noting that the interaction of the cysteamine stable selfassembled monolayer on the AuNPs/GCE surface and the covalent attachment of terephthalaldehyde via amide couplingwith theamine groups in the cysteamine and aptamer, respectively, resulted in the covalent attachment of the aptamer to AuNPs/GCE. The presence of gold nanoparticles both on surface of the glassy carbon electrode and in the end of the aptamer, can provide advantages such as increase of active surface area, high acceleration of the electron transfer and improved electrochemical signal, respectively. The decrease in the peak current of [Fe(CN)6]3−/4− as the probe redox with increase of cocaine concentration, in differential pulse voltammetry as the measuring technique, from 5 pM up to 5 nM was linear and an unprecedented detection limit of 0.5 pM was yielded. Furthermore, the effect of some common analgesic drugs as the potential interferents were investigated and also, to evaluate practical application of the proposed nanoaptasensor human blood serum sample as a real sample was used. Simple preparation, low operation cost, speed and validity are the decisive factors of this method motivating its application to biosensing investigation.
Efficient Determination of Butylated Hydroxyanisole Using an Electrochemical Sensor Based on Cobalt Oxide Nanoparticles Modified Electrode
Abstract
Efficient Determination of Butylated Hydroxyanisole Using an Electrochemical Sensor Based on Cobalt Oxide Nanoparticles Modified Electrode
A simple and reliable electrochemical sensor based on cobalt oxide nanoparticles modified glassy carbon electrode (GCE/CoOxNPs) for determination of butylated hydroxyanisole is presented here. The nanoparticles were fabricated by electrodepositing method. The modified electrode shows excellent catalytic activity toward butylated hydroxyanisole oxidation in pH 12.0 phosphate buffer solution (PBS). The detection limit (S/N = 3), sensitivity and catalytic rate constant (kcat) of the modified electrode toward butylated hydroxyanisole were 2.9 μM, 5.1 nA μM-1 and 1.1 × 104 M-1 s-1, respectively, at linear concentration rang up to 1350 μM. The capability of the modified electrode for direct butylated hydroxyanisole quantification in real samples is also discussed. This modified electrode shows many advantages such as good catalytic activity, good reproducibility, simple preparation procedure and long-term stability of signal response during butylated hydroxyanisole oxidation. In this report, compared with most cases previously reported, the detection potential of the BHA occurs at a lower potential
Covalent attachment of aptamer onto nanocomposite as a high performance electrochemical sensing platform: Fabrication of an ultra-sensitive ibuprofen electrochemical aptasensor
Abstract
Covalent attachment of aptamer onto nanocomposite as a high performance electrochemical sensing platform: Fabrication of an ultra-sensitive ibuprofen electrochemical aptasensor
In the present study, we report a selective electrochemical aptasensor for the ultrasensitive detection of an antiinflammatory drug, ibuprofen (IBP). The proposed system was achieved by the modification of a glassy carbon electrode (GCE) with multiwalled carbon nanotubes/ionic liquid/chitosan (MWCNTs/IL/Chit) nanocomposite and the covalent immobilization of the IBP specific aptamer (Apt) onto the modified electrode surface followed by methylene blue (MB) intercalated onto the Apt as the electrochemical redox marker. Upon the incubation of the IBP as a target in the proposed aptasensor, the peak current ofMB decreases due to the formation of the Apt- IBP complex and the displacement of MB from the immobilized Apt onto the modified electrode surface. The nanocomposite not only increases the electrode surface area and accelerate the electron transfer kinetics but also it provides a highly stable matrix to enhance the loading amount of the Apt DNA sequence. Through differential pulse voltammetry (DPV) experiments, it was found that the proposed aptasensor could detect the IBP with a linear range (70 pM up to 6 μM) and the detection limit (LOD) as low as 20 pM. The results showed that the aptasensor had good sensitivity, stability, reproducibility, and specificity to detect the IBP. The proposed aptasensor was successfully applied for measuring the IBP concentration in real samples. Based on our experiments we can say that the present method proposes new horizons for the development of other aptasensors for diagnostic application in biosensing.
An electrochemical dopamine aptasensor incorporating silver nanoparticle, functionalized carbon nanotubes and graphene oxide for signal amplification
Abstract
An electrochemical dopamine aptasensor incorporating silver nanoparticle, functionalized carbon nanotubes and graphene oxide for signal amplification
In this work, immobilization of a dopamine (DA) aptamer was performed at the surface of an amino functionalized silver nanoparticle-carbon nanotube graphene oxide (AgNPs/CNTs/GO) nanocomposite. A 58-mer DA-aptamer was immobilized through the formation of phosphoramidate bonds between the amino group of chitosan and the phosphate group of the aptamer at the 5′ end. An AgNPs/CNTs/GO nanocomposite was employed as a highly catalytic label for electrochemical detection of DA based on electrocatalytic activity of the nanocomposite toward hydrogen peroxide (H2O2). Interaction of DA with the aptamer caused conformational changes of the aptamer which, in turn, decreased H2O2 oxidation and reduction peak currents. On the other hand, the presumed folding of the DA–aptamer complexes on the sensing interface inhibited the electrocatalytic activity of AgNPs/CNTs/GO toward H2O2. Sensitive quantitative detection of DA was carried out by monitoring the decrease of differential pulse voltammetric (DPV) responses of AgNPs/CNTs/GO nanocomposite toward H2O2 oxidation. The DPV signal linearly decreased with increased concentration of DA from 3 to 110 nmol L1 with a detection limit of 700719.23 pmol L1. Simple preparation, low operation cost, speed and validity are the decisive factors of this method motivating its application to biosensing investigation.
A label-free aptasensor based on polyethyleneimine wrapped carbon nanotubes in situ formed gold nanoparticles as signal probe for highly sensitive detection of dopamine
Abstract
A label-free aptasensor based on polyethyleneimine wrapped carbon nanotubes in situ formed gold nanoparticles as signal probe for highly sensitive detection of dopamine
Herein, a highly sensitive and selective aptamer biosensor for quantitative detection of a model target, dopamine (DA), was developed by using a gold (Au) electrode modified with highly dispersed gold nanoparticles (AuNPs) and acid-oxidized carbon nanotubes (CNTs-COOH) functionalized with polyethyleneimine (PEI). Amine-terminated12- mercaptureprobe (ssDNA1) as a capture probe and specific DA-aptamer (ssDNA2) as a detection probe was immobilized on the surface of a modified electrode via the formation of covalent amide bond and hybridization, respectively. Methylene blue (MB) was used as the redox probe, which was intercalated into the aptamer through the specific interaction with its guanine bases. In the presence of DA, the interaction between aptamer and DA displaced theMB fromthe electrode surface, rendering a lowered electrochemical signal attributed to decreased amount of adsorbedMB. The developed electrochemical DA aptasensor showed a good linear response to DA from 5 to 300 nM with detection limit of 2.1 nM. The biosensor also exhibited satisfactory selectivity and could be successfully used to detect DA in blood serum sample. ©
Design and characterization of electrochemical dopamineeaptamer as convenient and integrated sensing platform
Abstract
Design and characterization of electrochemical dopamineeaptamer as convenient and integrated sensing platform
Here, an ultrasensitive label-free electrochemical aptasensor was developed for dopamine (DA) detection. Construction of the aptasensor was carried out by electrodeposition of goldeplatinum nanoparticles (AuePtNPs) on glassy carbon (GC) electrode modified with acid-oxidized carbon nanotubes (CNTs eCOOH). A designed complementary amine-capped capture probe (ssDNA1) was immobilized at the surface of PtNPs/CNTseCOOH/GC electrode through the covalent amide bonds formed by the carboxyl groups on the nanotubes and the amino groups on the oligonucleotides. DA-specific aptamer was attached onto the electrode surface through hybridization with the ssDNA1. Methylene blue (MB) was used as an electrochemical indicator that was intercalated into the aptamer through the specific interaction with its guanine bases. In the presence of DA, the interaction between aptamer and DA displaced the MB from the electrode surface, rendering a lowered electrochemical signal attributed to a decreased amount of adsorbed MB. This phenomenon can be applied for DA detection. The peak current of probe (MB) linearly decreased over a DA concentration range of 1e30 nM with a detection limit of 0.22 nM.
Bifunctional impedimetric sensors based on azodicarboxamide supported on modified graphene nanosheets
Abstract
Bifunctional impedimetric sensors based on azodicarboxamide supported on modified graphene nanosheets
Herein, gold-coated graphene oxide nanosheets hybrid material (GO/AuNPs) with exceptional physical and chemical properties has been utilized as a novel platform for electrode modification. The synthetic method of GO/AuNPs involves anon-covalent functionalization of exfoliated GO with AuNPs based on the reduction of the Au(III) complex by sodium citrate. The prepared GO/AuNPs hybrid exhibits the dispersion of high density AuNPs which were densely decorated on the large surface area of GO. The GO/AuNPs modified glassy carbon (GC) electrode was employed as a sensing platform to immobilize azodicarboxamide (ACA). The morphology, structure and electrochemical performance of the sensor were characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results indicate that the modified electrode has a notable bifunctional catalytic activity. Electrocatalytic oxidations of cysteine and electrocatalytic reduction of iodate at the surface of modified electrode were investigated with different technique.
Electrocatalytic oxidation behavior of NADH at Pt/Fe3O4/ reduced-graphene oxide nanohybrids modified glassy carbon electrode and its determination
Abstract
Electrocatalytic oxidation behavior of NADH at Pt/Fe3O4/ reduced-graphene oxide nanohybrids modified glassy carbon electrode and its determination
We have developed Pt/Fe3O4/reduced-graphene oxide nanohybrids modified glassy carbon (Pt/Fe3O4/RGO/GC) electrode as a novel system for the preparation of electrochemical sensing platform. Characterization of asmade composite was determined using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and energy-dispersive analysis of X-ray (EDAX) where the Pt, Fe, Si, O and C elementswere observed. The Pt/Fe3O4/RGO/GC electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Due to the synergistic effect between Pt, Fe3O4 and RGO, the nanohybrid exhibited excellent performance toward dihydronicotinamide adenine dinucleotide (NADH) oxidation in 0.1Mphosphate buffer solution, pH 7.0, with a low detection limit of 5 nM.
Separation of Ag(I) Ions from Lepidium draba L. Plant and Water and Standard Samples by Carrier Element-Free Coprecipitation Method Prior to their Flame Atomic Absorption Spectrometric Determination
Abstract
Separation of Ag(I) Ions from Lepidium draba L. Plant and Water and Standard Samples by Carrier Element-Free Coprecipitation Method Prior to their Flame Atomic Absorption Spectrometric Determination
In this work, silver iodide (Ag(I)) ions were separated via the carrier elementfree coprecipitation (CEFC) method using an organic coprecipitating agent, 1,6-diamino-4-(4-chlornphenyl)-2-oxo-1,2-dihydropyridine-3,5-dicarbonitrile [DCODD] prior to its determination by flame atomic absorption spectrometry (FAAS). Analytical parameters including pH of aqueous solution, amount of DCODD, standing time, centrifugation rate and time, and sample volume were studied and optimized. Under the best experimental conditions, it was found that extraction can be performed from the sample volume of 500.0 for silver ion (preconcentration factor of 100.0). Linearity was maintained between 0.006 and 1.50 μg.mL−1 for silver. Detection limit for silver based on 3Sb was 1.60 ng.mL−1. The relative standard deviation of eight replicate measurements of 0.20 μg.mL−1of silver was 2.10%. Finally, the developed method was successfully applied to extraction and determination of the silver ions in the Lepidium draba L plant, water and standard samples and satisfactory results were obtained.
Electroanalytical sensing of Cd2+based on metal–organic frameworkmodified carbon paste electrode
Abstract
Electroanalytical sensing of Cd2+based on metal–organic frameworkmodified carbon paste electrode
This paper reports, for the first time, the fabrication and characterization of sensitive electrochemicalsensor for the efficient detection of cadmium ion using metal organic framework (MOF). TMU-16-NH2([Zn2(NH2-BDC)2(4-bpdh)]·3DMF) a kind of metal organic frame works was used as a modifier. The inter-action between cadmium and amine groups of TMU-16-NH2are conditioned by dative attachment thatcaused Cd2+-N complexation by soft–soft interactions. To achieve the highest efficiency of the sensor,effective factors on analytical response such as pH, deposition potential and deposition time have beenoptimized. Under optimal experimental conditions, the oxidation current increased by the addition ofcadmium in the sample and dynamic ranges obtained from 0.7 to 120 by differential pulse voltammetry(DPV). This method exhibited a lower limit of detection (LOD) of 0.2 g L−1(S/N = 3). The presented workdemonstrates that the MOFs are effective materials to fabricate efficient electrochemical sensors for theeasy and costly effective detection of cadmium ions in solutions.
Electroanalytical sensing of Cd2+ based on metal–organic framework modified carbon paste electrode
Abstract
Electroanalytical sensing of Cd2+ based on metal–organic framework modified carbon paste electrode
This paper reports, for the first time, the fabrication and characterization of sensitive electrochemical sensor for the efficient detection of cadmium ion using metal organic framework (MOF). TMU-16-NH2 ([Zn2(NH2-BDC)2(4-bpdh)]·3DMF) a kind of metal organic frame works was used as a modifier. The interaction between cadmium and amine groups of TMU-16-NH2 are conditioned by dative attachment that caused Cd2+-N complexation by soft–soft interactions. To achieve the highest efficiency of the sensor, effective factors on analytical response such as pH, deposition potential and deposition time have been optimized. Under optimal experimental conditions, the oxidation current increased by the addition of cadmium in the sample and dynamic ranges obtained from 0.7 to 120 by differential pulse voltammetry (DPV). This method exhibited a lower limit of detection (LOD) of 0.2 g L−1 (S/N = 3). The presented work demonstrates that the MOFs are effective materials to fabricate efficient electrochemical sensors for the easy and costly effective detection of cadmium ions in solutions.
Effect of metal alloying on morphology and catalytic activity of platinum-based nanostructured thin films in methanol oxidation reaction†
Abstract
Effect of metal alloying on morphology and catalytic activity of platinum-based nanostructured thin films in methanol oxidation reaction†
Direct methanol fuel cells are considered to be promising sources of green power. However, their commercialization is seriously hindered by the high cost of Pt. The use of an alloy is an effective way to solve the problem. According to Duan and Lee et al., nanosheets and nanobranches (similar to dendrimers) are highly favored for superior catalytic performances due to their geometric properties. In this paper a facile and efficient approach for the synthesis of binary, ternary and tetrametallic alloy thin films at a liquid–liquid interface was demonstrated. Transmission electron microscopy exhibited a nanodendritic structure for PtPdNiFeFe2O3, a nanosheet structure for PtPdNi or PtPdNiZn, and spherical nanostructures for PdNi, PtNi and PtPdNiSn alloy thin films. The synthesized PtPdNiFeFe2O3 nanodendrimers, and PtPdNiZn and PtPdNi alloy nanosheets exhibit a higher electrocatalytic activity toward methanol oxidation than other binary alloy thin films such as a PdNi thin film, and monometallic Pt or Pd thin films which may be attributed to their large surface area. Due to simple implementation, the proposed approach can be considered as a general and powerful strategy to synthesize ternary and tetrametallic alloy electrocatalysts with high surface area.
Development of sensitive amperometric hydrogen peroxide sensor using a CuNPs/MB/MWCNT-C60-Cs-IL nanocomposite modified glassy carbon electrode
Abstract
Development of sensitive amperometric hydrogen peroxide sensor using a CuNPs/MB/MWCNT-C60-Cs-IL nanocomposite modified glassy carbon electrode
A sensitive hydrogen peroxide (H2O2) sensor was constructed based on copper nanoparticles/methylene blue/ multiwall carbon nanotubes–fullerene–chitosan–ionic liquid (CuNPs/MB/MWCNTs–C60–Cs–IL) nanocomposites. TheMB/MWCNTs–C60–Cs–IL and CuNPswere modified glassy carbon electrode (GCE) by the physical adsorption and electrodeposition of copper nitrate solution, respectively. The physical morphology and chemical composition of the surface of modified electrode was investigated by scanning electron microscopy (SEM) and energydispersive X-ray spectroscopy (EDS), respectively. The electrochemical properties of CuNPs/MB/MWCNTs–C60– Cs–IL/GCE were investigated by cyclic voltammetry (CV) and amperometry techniques and the sensor exhibited remarkably strong electrocatalytic activities toward the reduction of hydrogen peroxide. The peak currents possess a linear relationshipwith the concentration of H2O2 in the range of 0.2 μMto 2.0mM, and the detection limit is 55.0 nM (S/N = 3). In addition, the modified electrode was used to determine H2O2 concentration in human blood serum sample with satisfactory results.
Highly sensitive colorimetric determination of malathion using gold nanoparticles
Abstract
Highly sensitive colorimetric determination of malathion using gold nanoparticles
A highly sensitive method is presented for the colorimetric determination of malathion using gold nanoparticles (AuNPs). In this approach, the synthesized AuNPs solution was stabilized by the citrate anions as their repulsion protected the AuNPs from aggregation. The synthesized AuNPs were characterized morphologically by using transmission electron microscopy technique. Malathion caps the surface of AuNPs and induces the aggregation of AuNPs in Britton–Robinson buffer solution. The reaction was monitored spectrophotometrically by measuring the decrease in the plasmon resonance band of the AuNPs at 527 nm after 9 min. The effect of reaction variables on the reaction sensitivity was investigated and furthermore, the interference of common ions was effectively avoided. The calibration curve is linear over the concentration range 3.3 × 107 to 3.3 × 106 mol/L of malathion with good precision and accuracy and the detection limit was down to 1.5 × 107 mol/L. The developed approach does not use complex and expensive instruments. The high sensitivity of the proposed method allowed its successful application to wheat and water samples. Thus, the proposed strategy can serve as a powerful method for the rapid diagnosis of malathion in agriculture products.
Conformation switchingofanaptamerbasedoncocaineenhancement on asurfaceofmodified GCE
Abstract
Conformation switchingofanaptamerbasedoncocaineenhancement on asurfaceofmodified GCE
An ultrasensitiveaptasensorwasfabricatedasanelectrochemicalnanotoolbasedontheconformation switching ofanaptamer(Apt).TheAptwhichwascovalentlyattachedonthesurfaceofaglassycarbon electrode (GCE)coveredwithcadmiumtelluride(CdTe)quantumdots(QDs)worksasauniquemodifier for assayingcocaine.TheAptwascombinedwithcocainetoformathree-wayjunctioncomplex;this complexincreasedthesterichindranceofthemodified GCEsurfaceandresultedinavariationofthe corresponding currentofaredoxprobe.Inthepresentstudy,DPVtechniqueforcocainedetectionwas applied andresultedinanunprecedenteddetectionlimit(LOD)of5.070.1pmolL1, whichismore sensitivethanpreviouslyreportedmethods.Oneofthegreatestadvantagesofthisaptasensoristhe elimination ofenzymesorantibodies.Itisalsorelativelyahighlysensitive,simple,reproducible,and controllable nanotool.Likewise,itcanbeeasilyminiaturized,whichisanecessaryconditionforthehigh- throughput systemandon-siteapplications.Theofferednanotoolhasagreatpromisefortheroutine analysisoftheultra-traceamountsofcocaine,whichisimportantforlawenforcementandclinical medicine. Itisnotabletosaythatfurtherattemptsareunderwayinourlaboratoryfortheconstructionof other aptasensorswithhigherperformanceforspecific targetssuchasthedetectionofmethadone (MTD) andibuprofen(IBP).
The use of a signal amplification strategy for the fabrication of a TNT impedimetric nanoaptasensor based on electrodeposited NiONPsimmobilized onto a GCE surface
Abstract
The use of a signal amplification strategy for the fabrication of a TNT impedimetric nanoaptasensor based on electrodeposited NiONPsimmobilized onto a GCE surface
tThis study reports on the evaluation of NiONPs layer as an efficient platform in designing a TNT nanoap-tasensor. Based on this strategy, a film of electrodeposited NiONPs was immobilized onto the surface ofa GCE. This film was used as a capture layer for the covalent attachment of Apt, which was a receptorelement with regard to TNT. By incubating TNT onto the surface of the prepared Apt/NiONPs/GCE asa proposed nanoaptasensor, the Apt/TNT complex was formed and the changes of the electrochemicalsignal were evaluated with the EIS technique. The superior transduction platform and the Apts weredensely populated at the surface of the modified electrode lowered the LOD, 33.5 aM. Furthermore, theexcellent antifouling ability of the NiONPs/GCE improves the operational stability and repeatability ofthe proposed nanoaptasensor. While most of the conventional approaches have used multistep chemicalmethods for modeling an apasensor, our proposed strategy provides the notable advantages the use of asingle-step modification without employing any complex agent, the use of a simple procedure and notbeing time-consuming. The results indicated that the modification of a GCE with the electrodepositedNiONPs layer can expand the application of this strategy to develop some biosensors based on DNA inorder to detect various targets.
An impedimetric aptasensor based on water soluble cadmium telluride (CdTe) quantum dots (QDs) for detection of ibuprofen
Abstract
An impedimetric aptasensor based on water soluble cadmium telluride (CdTe) quantum dots (QDs) for detection of ibuprofen
An impedimetric aptasensor is reported here for the ultrasensitive detection of ibuprofen (IBP) using water soluble cadmium telluride (CdTe) quantum dots (QDs) as the efficient electrochemical platform. The CdTe QD layer was used as a quite suitable interface for the subsequent conjugation of the aptamer (Apt). CdTe QDs owing to their large surface area, caused the increase in the amount of Apt absorbed on the modified electrode which resulted in enhanced signal response. Also, their ion centers may have had a major role on amplifying the signal. In this method, the IBP specific Apt is immobilized onto the glassy carbon electrode (GCE) and through the specific binding of the IBP and its Apt, the IBP/Apt complex is formed.More importantly, the developed strategy shows highly sensitive responses to IBP, responsesmore sensitive than those of previously reportedmethods. Under optimal conditions, IBP was detected by electrochemical impedance spectroscopy (EIS) quantitatively. Calibration curve for IBP concentration was linear up to 20 μM and the detection limit was as low as 16 pM. The developed aptasensor was successfully used to detect IBP in real samples such as spiked human serum and pharmaceutical formulations. The use of CdTe QDs as a unique platform and the elimination of antibodies or enzymes for the amplified detection of the IBP, are the advantages of the developed aptasensor. Our work will shed light on new diagnostic applications of aptasensors and is quite promising as an alternative approach for various target assays
Layer-by-layer assembly of gold nanoparticles and cysteamine on gold electrode for immunosensing of human chorionic gonadotropin at picogram levels
Abstract
Layer-by-layer assembly of gold nanoparticles and cysteamine on gold electrode for immunosensing of human chorionic gonadotropin at picogram levels
The development of an electrochemical immunosensor for the detection of human chorionic gonadotropin (hCG) is described with a limit of detection as low as 0.3 pg mL−1 in phosphate buffer. In this immunosensor, cysteamine (Cys) and gold nanoparticles (AuNPs) were used to immobilize an anti-hCG monoclonal antibody onto a gold electrode (GE). The structure of AuNPs has been confirmed by EDS, SEM, and TEM analysis. Due to the large specific surface area and excellent electrical conductivity of AuNPs, electron transfer was promoted and the amount of hCG antibody was enhanced significantly. A systematic study on the effects of experimental parameters such as pH, incubation time in the hCG solution and urea solution used for experiments on the binding between the immobilized antibody and hCG has been carried out. Under optimal experimental parameters, differential pulse voltammetry (DPV) signal changes of the [Fe(CN)6]3−/4− are used to detect hCG with two broad linear ranges: 0.001 to 0.2 and 0.2 to 60.7 ng mL−1. The LOD value proves more sensitive in comparisonwith previously reported methods. The prepared immunosensor showed high sensitivity and stability. In addition, the immunosensor was successfully used for the determination of hCG in human serum.
Voltammetric immunosensor for human chorionic gonadotropin using a glassy carbon electrode modified with silver nanoparticles and a nanocomposite composed of graphene, chitosan and ionic liquid, and using riboflavin as a redox probe
Abstract
Voltammetric immunosensor for human chorionic gonadotropin using a glassy carbon electrode modified with silver nanoparticles and a nanocomposite composed of graphene, chitosan and ionic liquid, and using riboflavin as a redox probe
The aim of this study was to develop an electrochemical immunoassay system to detect of human chorionic gonadotropin (hCG). The immunosensor was constructed by covalent immobilization of silver nanoparticles (AgNPs) onto a nanocomposite containing graphene, chitosan (Chit) and 1- methyl-3-octylimidazolium tetrafluoroborate as ionic liquid (IL). Silver nanoparticles were used as a linker to immobilize hCG antibody onto the modified electrode. The amino groups of the antibody were covalently attached to an AgNP/g-ILChit nanocomposite. Cyclic voltammetry and electrochemical impedance spectroscopy were employed to characterize the assembly process of the immunosensor. Riboflavin was used as the redox probe. Differential pulse voltammetry demonstrated that the formation of antibody–antigen complexes decreases the peak current of redox pair at the AgNP/Gr-IL-Chit/ GCE (at a working potential of−0.38 V). The signal changes of riboflavin are used to detect hCG with broad response ranges from 0.0212 to 530 mIU.mL−1 and a low detection limit of 0.0066± 0.02 mIU.mL−1.
Development of Nonenzymatic Hydrogen Peroxide Sensor Based on Successive Pd-Ag Electrodeposited Nanoparticles on Glassy Carbon Electrode
Abstract
Development of Nonenzymatic Hydrogen Peroxide Sensor Based on Successive Pd-Ag Electrodeposited Nanoparticles on Glassy Carbon Electrode
A novel strategy to fabricate hydrogen peroxide (H2O2) sensor was developed by electrodepositing palladium¢silver nanoparticles (NPs) on a glassy carbon electrode. The morphology of the modified electrode was characterized by Scanning electron microscopy (SEM). The result of electrochemical experiments showed that such constructed sensor had a favorable catalytic ability, high sensitivity, excellent selectivity towards reduction of hydrogen peroxide (H2O2). The response to H2O2 is linear in the range between 0.30 mM to 2.50 mM, and the detection limit is 0.1 mM (at an S/N of 3).
Graphene quantum dots as novel and green nano-materials for thevisible-light-driven photocatalytic degradation of cationic dye
Abstract
Graphene quantum dots as novel and green nano-materials for thevisible-light-driven photocatalytic degradation of cationic dye
tIn this paper, we have introduced a novel property of graphene quantum dots (GQDs) as efficient nano-materials for degradation of organic pollutant dyes based on the photocatalytic behavior of GQDs undervisible light irradiation. GQD samples were synthesized directly through pyrolyzing citric acid method.The synthesized GQDs were characterized by various techniques including colorimetry, transmissionelectron microscopy (TEM), and UV–vis absorption, Raman spectroscopy, fluorescence spectroscopy, andzeta potential measurements. In this study, a cationic dye (i.e., New Fuchsin) was chosen as a modelmolecule to investigate catalytic behavior of the prepared GQDs as green nanomaterials. The influenceof experimental parameters such as pH of the dye solution, contacting time, dosage of GQDs, and initialconcentration of NF dye on the degradation efficiency of GQD were studied. The possible mechanisms ofdegradation of NF based on GQDs under visible light were discussed, too.
Synthesis and application of ion-imprinted polymer nanoparticles for the extraction and preconcentration of mercury in water and food samples employing cold vapor atomic absorption spectrometry
Abstract
Synthesis and application of ion-imprinted polymer nanoparticles for the extraction and preconcentration of mercury in water and food samples employing cold vapor atomic absorption spectrometry
We describe a nanosized Hg(II)-imprinted polymer that was prepared from methacrylic acid as functional monomer, ethyleneglycol dimethacrylate as cross-linker, 2,2′-azobisisobutyronitrile (AIBN) as radical initiator, 2, 2′-di pyrydyl amine as a specific ligand, and Hg (II) as the template ions by precipitation polymerization method in methanol as the progeny solvent. Batch adsorption experiments were carried out as a function of pH, Hg (II) imprinted polymer amount, adsorption and desorption time, volume, and concentration of eluent. The synthesized polymer particles were characterized physically and morphologically by using infrared spectroscopy, thermogravimetric analysis, Xray diffraction, and scanning electron microscopic techniques. The maximum adsorption capacity of the ionimprinted and non-imprinted sorbent was 27.96 and 7.89 mg g−1, respectively. Under optimal conditions, the detection limit for mercury was 0.01 μg L−1 and the relative standard deviation was 3.2 % (n=6) at the 1.00 μg L−1. The procedure was applied to determination of mercury in fish and water samples with satisfactory results.
Using electrochemical oxidation of Rutin in modeling a novel andsensitive immunosensor based on Pt nanoparticle and graphene–ionicliquid–chitosan nanocomposite to detect human chorionicgonadotropin
Abstract
Using electrochemical oxidation of Rutin in modeling a novel andsensitive immunosensor based on Pt nanoparticle and graphene–ionicliquid–chitosan nanocomposite to detect human chorionicgonadotropin
tThis study aims at developing an innovative electrochemical immunoassay system for an ultrasensitivedetection of human chorionic gonadotropin (hCG). hCG is a secretion of the placenta during pregnancyand gestational trophoblastic diseases. It increases as a consequence of abnormal placental invasion andplacental immaturity. Thus, an exact diagnosis of the concentration of hCG in urine or serum plays animportant role in monitoring trophoblastic diseases in all modern immunological pregnancy tests. Inthis work, a novel immunosensor is constructed by covalent immobilization of Pt nanoparticles (PtNPs)onto robust nanocomposite containing graphene (Gr), chitosan (Chit) and 1-methyl-3-octyl imidazoliumtetrafluoroborate as ionic liquid (IL) (Gr–IL–Chit). The nanocomposite not only led to increase the elec-trode surface area and accelerate the electron transfer kinetics, but also it could provide a highly stablematrix to enhance the loading amount of the nanoparticles. PtNPs acts as a linker to immobilize hCG anti-body onto the modified electrode. The amine groups of the antibody are covalently attached to PtNPs.Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spec-troscopy (EIS) were employed to trace the assembly process of the immunosensor. In this study, we usedRutin (RU) for the first time as the redox probe in the development of the electrochemical immunosensor.Upon biorecognition hCG to its antibody, peak current of RU decreased due to the formation of hCG–antihCG complex. Through differential pulse voltammetry (DVP) experiments, it was found that proposedimmunosensor could detect hCG at two broad linear ranges: 0.00106–2.12 and 2.12–350 mIU/mL and alow detection limit of 0.00035 mIU/mL. The immunosensor was found stable, reproducible, and highlyspecific for hCG detection.
Fabricationofanultrasensitiveibuprofennanoaptasensorbasedon covalentattachmentofaptamertoelectrochemicallydepositedgold- nanoparticles onglassycarbonelectrode
Abstract
Fabricationofanultrasensitiveibuprofennanoaptasensorbasedon covalentattachmentofaptamertoelectrochemicallydepositedgold- nanoparticles onglassycarbonelectrode
The paperreportsthedevelopmentofanultrasensitivenanoaptasensorbasedonthecovalentattach- ment ofanaptamer(Apt)togold-nanoparticles(AuNPs)depositedonthesurfaceofaglassycarbon electrode (GCE)astheuniqueplatform.Thedevelopednanoaptasensorwasutilizedtoassaytheanti- inflammatorydrug,ibuprofen(IBP).Thesensingplatformwasfabricatedusingasingle-stageelectro- deposite approach.Itisworthnotingthattheproposednanoaptasensorcombinestheadvantagesofthe deposition ofneatlyarrangedAuNPs(enlargedactivesurfaceareaandstrengthenedelectrochemical signal) andtheeliminationofenzymesorantibodiesfortheamplified detectionofIBP,withthecovalent attachment oftheApttothesurfaceofthemodified electrode.Moreover,thenewlydevelopedna- noaptasensor embracesanumberofattractivefeaturessuchaseaseoffabrication,lowdetectionlimit, excellentselectivity,goodstabilityandawidelinearrangewithrespecttoIBP.Meanwhile,interference of commoninterferinganalgesicdrugswaseffectivelyavoided.Inoptimizedempiricalconditions,the response currentofthenanoaptasensorislineartoIBPconcentrationsfrom0.005nmol1 to 7nmol1 with thedetectionlimit(LOD)asaccurateas0.5pmol1. ThisLODvalueprovesmoresensitivein comparison withpreviouslyreportedmethods.Thus,thefabricatednanoaptasensorcanserveasa powerfulsensorforrapiddiagnosisofIBPinhumanbloodsamplesandshowsgreatpotentialfor practical bioapplication.
Development of nonenzymatic hydrogen peroxide sensor based on catalytic properties of copper nanoparticles/Rutin/MWCNTs/IL/Chit
Abstract
Development of nonenzymatic hydrogen peroxide sensor based on catalytic properties of copper nanoparticles/Rutin/MWCNTs/IL/Chit
A newelectrochemical sensor based on copper nanoparticles for detection of hydrogen peroxide has been developed. Copper nanoparticles/Rutin/Multiwall Carbon Nanotubes/Ionic liquid/Chitosan modified glassy carbon electrode (CuNPs/Rutin/MWCNTs/IL/Chit/GCE) prepared by consecutive coating of MWCNTs/IL/Chit nanocomposite and rutin on the GCE, followed by the electrodeposition of copper. Surface physical characteristics of modified electrode were studied by scanning electron microscopy (SEM). The electrochemical performance of the sensor for detection of H2O2 was investigated by cyclic voltammetry and chronoamperometry techniques. The modified electrode exhibits an enhanced electrocatalytic property, lowworking potential, high sensitivity, excellent selectivity, good stability, and fast amperometric sensing towards reduction of hydrogen peroxide. The response to H2O2 is linear in the range between 0.35 μM to 2500 μM, and the detection limit is 0.11 μM.
Characterization of Polypyrrole-hydroxyethylcellulose/TiO2 Nanocomposite: Thermal Properties and AFM Analysis
Abstract
Characterization of Polypyrrole-hydroxyethylcellulose/TiO2 Nanocomposite: Thermal Properties and AFM Analysis
Polypyrrole–hydroxyethylcellulose/TitaniumDioxide (PPy-HEC/TiO2) nanocomposite was synthesized via in situ chemical oxidative polymerization method at room temperature in water and water/ethyl acetate solution in the presence of ferric chloride (FeCl3). The effect of TiO2 nanoparticles and HEC on the characteristics of products such as thermal stability and morphology was investigated. The fabricated composite and nanocomposite morphology and structure were analyzed by atomic forced microscopy (AFM), Scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and Thermogravimetric analysis (TGA). The AFM images of products indicated that hydroxyethylcellulose decreased the surface roughness of nanocomposite. Also, hydroxyethylcellulose decreased particle size. The molecular structure of product was determined by FTIR spectroscopy. The results of XRD confirmed crystalline structure of TiO2 nanoparticles and partly crystalline structure of PPy-HEC/TiO2 nanocomposite. TGA was used to study the thermal behavior of nanocomposite. The TGA curves indicated that TiO2 and HEC enhanced thermal stability of products.
Novel electrochemical sensor based on carbon nanodots/chitosan nanocomposite for the detection of tryptophan
Abstract
Novel electrochemical sensor based on carbon nanodots/chitosan nanocomposite for the detection of tryptophan
A modified glassy carbon electrode (GCE) was prepared by incorporating carbon nanodots (CNDs) and chitosan (CS) for the determination of tryptophan (Trp). In this method, the electrochemical response of Trp was examined and the irreversible electrochemical oxidation and two electrons involved in the process of Trp were demonstrated. Because of good conductivity, large surface area, and excellent catalytic activity of CNDs, the CS and CNDs hybrid film extremely increased the electrochemical response of Trp, offering a highly sensitive electrochemical sensor for determination of Trp. The sensor showed a low detection limit of 90 nM and high sensitivity of 4 nA μM−1. The high stability and simplicity of prepared nanohybrid combined with excellent sensitivity and selectivity of the sensor may bring novel and interesting applications for different diagnoses. As a way forward, the proposed methodology is promised for fabrication of the other effective and sensitive sensors
Amperometric Detection of Isoprenaline Based on Glassy Carbon Electrode Modified by Iridium Oxide Nanoparticles
Abstract
Amperometric Detection of Isoprenaline Based on Glassy Carbon Electrode Modified by Iridium Oxide Nanoparticles
A simple and sensitive electrochemical sensor by using a glassy carbon electrode modified by iridium oxide nanoparticles (GCE/IrOxNPs) was constructed and utilized to determine isoprenaline (IP). This sensor was used successfully for IP determination in human urine samples. IrOxNPs are grown on a GCE by electrodepositing method. Various experimental parameters influencing the electrochemical behavior of the modified electrode were optimized by varying the scan rates and pH. Compared with a bare GCE, the GCE/IrOxNPs exhibits a distinct shift of the oxidation potential of IP in the cathodic direction and a marked enhancement of the current response. The results showed that GCE/IrOxNPs exhibited excellent electrochemical activity towards IP in pH 7.0 phosphate buffer solution (PBS). The detection limit, sensitivity and catalytic rate constant (kcat) of the modified electrode toward IP were 90 nmol L-1, 17.3 nA μmol-1 L and 1.6 × 104 mol-1 L s-1, respectively, at linear concentration rang up to 2500 μmol L-1. The modified electrode displayed linear responses to IP in amperometry assays in real urine, with a detection limit of 120 nmol L-1.
Synthesis and application of ion-imprinted polymer nanoparticles for the extraction and preconcentration of copper ions in environmental water samples
Abstract
Synthesis and application of ion-imprinted polymer nanoparticles for the extraction and preconcentration of copper ions in environmental water samples
Novel Cu(II) ion-imprinted polymers (Cu-IIP) nanoparticles were prepared by using Cu(II) ionthiosemicarbazide complex as the template molecule and methacrylic acid, ethylene glycol dimethacrylate (EGDMA), and 2,2′azobisisobutyronitrile (AIBN) as the functional monomer, cross-linker, and the radical initiator, respectively. The synthesized polymer nanoparticles were characterized by using infrared spectroscopy (IR), thermo gravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopic (SEM) techniques. Some parameters such as pH, weight of the polymer, adsorption time, elution time, eluent type, and eluent volume which affect the extraction efficiency of the polymer were studied. In the proposed method, the maximum sorbent capacity of the ion-imprinted polymer was calculated to be 38.8mg g−1. The preconcentration factor, relative standard deviation, and limit of detection of the method were found to be 80, 1.7 %, and 0.003 μg mL−1, respectively. The prepared ion-imprinted polymer nanoparticles have an increased selectivity toward Cu (II) ions over a range of competing metal ions with the same charge and similar ionic radius. The method was applied to the determination of ultra trace levels of Cu2+ in environmental water samples with satisfactory results.
Synthesis and application of ion-imprinted polymer nanoparticles for the determination of nickel ions
Abstract
Synthesis and application of ion-imprinted polymer nanoparticles for the determination of nickel ions
Novel Ni(II) ion-imprinted polymers (Ni-IIP) nanoparticles were prepared by using Ni(II) ion–1,5-diphenyl carbazide (DPC) complex as the template molecule and methacrylic acid, ethylene glycol dimethacrylate (EGDMA) and 2,20-azobisisobutyronitrile (AIBN) as the functional monomer, cross-linker and the radical initiator, respectively. The synthesized polymer particles were characterized physically and morphologically by using infrared spectroscopy (IR), thermo gravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopic (SEM) techniques. Some parameters such as pH, weight of the polymer, adsorption time, elution time, eluent type and eluent volume which affects the efficiency of the polymer were studied. The preconcentration factor, relative standard deviation, and limit of detection of the method were found to be 100, 1.9%, and 0.002 lgmL1, respectively. The prepared ionimprinted polymer particles have an increased selectivity toward Ni(II) ions over a range of competing metal ions with the same charge and similar ionic radius. The method was applied to the determination of nickel in tomato and some water samples
A novel ultrasensitive aptasensor based on silver nanoparticlesmeasured via enhanced voltammetric response of electrochemicalreduction of riboflavin as redox probe for cocaine detection
Abstract
A novel ultrasensitive aptasensor based on silver nanoparticlesmeasured via enhanced voltammetric response of electrochemicalreduction of riboflavin as redox probe for cocaine detection
A novel, simple and selective aptasensor for ultrasensitive detection of the addictive drug, cocaine,is developed using the electrochemical transduction method. The aptasensor is constructed by cova-lent immobilization of aptamer-functionalized AgNPs on the MWCNTs/IL/Chit nanocomposite as thesensing interface which improves the conductivity and performance characteristics of the aptasensorand enhances the loading amount of the aptamer DNA sequence. In this study, riboflavin (RF) has beenused for the first time as the redox probe in the development of the electrochemical aptasensor for thediagnosis of cocaine. AgNPs lead to the acceleration of the electron transfer kinetics related to the reduc-tion of RF. The differential pulse voltammetric (DPV) signal of the RF linearly decreases with increasedconcentration of cocaine from 2 nM to 2.5 M with a detection limit (S/N = 3) of 150 pM. By using certainanalgesic drugs as the interfering agents, the excellent specificity of this sensing system for cocaine mea-surement is also demonstrated. Finally, the proposed aptasensor has successfully been used to detectcocaine in human serum samples
Synthesis and application of ion-imprinted polymer nanoparticles for the extraction and preconcentration of zinc ions
Abstract
Synthesis and application of ion-imprinted polymer nanoparticles for the extraction and preconcentration of zinc ions
A new Zinc (II) ion-imprinted polymer (IIPs) nanoparticles was synthesised for the separation and recovery of trace Zn (II) ion from food and water sample. Zn (II) IIP was prepared by copolymerisation of methyl methacrylate (monomer) and ethylene glycol dimethacrylate (cross-linker) in the presence of Zn (II)-N,N0-o-phenylene bis (salicylideneimine) ternary complex wherein Zn (II) ion is the imprint ion and is used to form the imprinted polymer. Moreover, control polymer (NIP) particles were similarly prepared without the zinc (II) ions. The unleached and leached IIP particles were characterised by X-ray diffraction, Fourier transform infra-red spectroscopy and scanning electron microscopy. The preconcentration of Zn2+ from aqueous solution was studied during rebinding with the leached IIP particles as a function of pH, the weight of the polymer material, the uptake and desorption times, the aqueous phase and the desorption volumes. Flame atomic absorption spectrometry was employed for determination of zinc in aqueous solution.
A highly selective and sensitive cocaine aptasensor based on covalent attachment of the aptamer-functionalized AuNPs onto nanocomposite as the support platform
Abstract
A highly selective and sensitive cocaine aptasensor based on covalent attachment of the aptamer-functionalized AuNPs onto nanocomposite as the support platform
Based on the conformational changes of the aptamer-functionalized gold nanoparticles (AuNPs) onto MWCNTs/IL/Chit nanocomposite as the support platform, we have developed a sensitive and selective electrochemical aptasensor for the detection of cocaine. The 50-amine-30-AuNP terminated aptamer is covalently attached to a MWCNTs/IL/Chit nanocomposite. The interaction of cocaine with the aptamer functionalized AuNP caused the aptamer to be folded and the AuNPs with negative charge at the end of the aptamer came to the near of electrode surface therefore, the electron transfer between ferricyanide (K3Fe(CN)6) as redox probe and electrode surface was inhibited. A decreased current of (K3Fe(CN)6) was monitored by differential pulse voltammetry technique. In an optimized condition the calibration curve for cocaine concentration was linear up to 11 mM with detection limit (signal-to-noise ratio of 3) of 100 pM. To test the selectivity of the prepared aptasensor sensing platform applicability, some analgesic drugs as the interferes were examined. The potential of the aptasensor was successfully applied for measuring cocaine concentration in human blood serum. Based on our experiments it can be said that the present method is absolutely beneficial in developing other electrochemical aptasensor.
High CO tolerance of Pt/Fe/Fe2O3 nanohybrid thin film suitable for methanol oxidation in alkaline medium
Abstract
High CO tolerance of Pt/Fe/Fe2O3 nanohybrid thin film suitable for methanol oxidation in alkaline medium
The toluene–water interface has traditionally been employed to prepare particle assemblies and films of metals and semiconductors. The interface between water and an organic liquid, however, has not been investigated sufficiently for possible use in preparing nanocrystals and thin films of magnetic alloys. In this article, we demonstrate the use of the liquid–liquid interface as a medium for preparing ultrathin films of magnetic Pt/Fe/Fe2O3 nanohybrid catalysts for methanol electrooxidation in NaOH medium. The resulting Pt/Fe/Fe2O3 hybrid catalyst shows the highest activity and CO tolerance (jf/jb ¼ 8.09) among all other catalysts that were tested up to now toward methanol electrooxidation. The results reported in this article demonstrate the versatility and potential of the liquid–liquid interface for preparing nanomaterials and ultrathin films and encourage further research in this area.
LIGANDLESS CLOUD POINT EXTRACTION OF TRACE AMOUNTS OF PALLADIUM AND RHODIUM IN ROAD DUST SAMPLES USING SPAN 80 PRIOR TO THEIR DETERMINATION BY FLAME ATOMIC ABSORPTION SPECTROMETRY
Abstract
LIGANDLESS CLOUD POINT EXTRACTION OF TRACE AMOUNTS OF PALLADIUM AND RHODIUM IN ROAD DUST SAMPLES USING SPAN 80 PRIOR TO THEIR DETERMINATION BY FLAME ATOMIC ABSORPTION SPECTROMETRY
In this study, a procedure is developed for cloud point extraction of Pd(II) and Rh(III) ions in aqueous solution using Span 80 (nonionic surfactant) prior to their determination by flame atomic absorption spectroscopy. This method is based on the extraction of Pd(II) and Rh(III) ions at a pH of 10 using Span 80 with no chelating agent. We investigated the effect of various parameters on the recovery of the analyte ions, including pH, equilibration temperature and time, concentration of Span 80, and ionic strength. Under the best experimental conditions, the limits of detection based on 3Sb for Pd(II) and Rh(III) ions were 1.3 and 1.2 ng mL−1, respectively. Seven replicate determinations of a mixture of 0.5 μg mL−1 palladium and rhodium ions gave a mean absorbance of 0.058 and 0.053 with relative standard deviations of 1.8 and 1.6%, respectively. The developed method was successfully applied to the extraction and determination of the palladium and rhodium ions in road dust and standard samples and satisfactory results were obtained.
Organometallic precursor route for the fabrication of PtSn bimetallic nanotubes and Pt3Sn/reduced-graphene oxide nanohybrid thin films at oilewater interface and study of their electrocatalytic activity in methanol oxidation
Abstract
Organometallic precursor route for the fabrication of PtSn bimetallic nanotubes and Pt3Sn/reduced-graphene oxide nanohybrid thin films at oilewater interface and study of their electrocatalytic activity in methanol oxidation
This report discusses synthesis of PtSn nanotubes and Pt3Sn reduced-graphene oxide (RGO) nanohybrid thin films via a simple reduction of organometallic precursors including [PtCl2(cod)], (cod ¼ cis, cis-1,5- cyclooctadiene), in the presence of [Sn(CH3)4] at tolueneewater interface. The structure and morphology of the thin films were characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive analysis of X-ray (EDAX) techniques. TEM measurements revealed that the PtSn bimetallic thin films contain nanotubes with diameters in the 8e10 nm range and 200e800 nm in length. However, TEM image of Pt3Sn/RGO bimetallic nanohybrid thin films showed a good distribution of bimetallic nanoparticles (NPs) on the RGO support with average diameter of 8 nm. The electrocatalytical activities of tin alloys thin films were evaluated using methanol as model molecule. The PtSn nanotubes and Pt3Sn/RGO nanohybrid thin films show a higher catalytic activity in methanol oxidation reaction than that for the Pt NPs films with the lower Pt loading
Electrochemical Detection of Persulfate at the Modified Glassy Carbon Electrode with Nanocomposite Containing Nano-Ruthenium Oxide/Thionine and Nano-Ruthenium Oxide/Celestine Blue
Abstract
Electrochemical Detection of Persulfate at the Modified Glassy Carbon Electrode with Nanocomposite Containing Nano-Ruthenium Oxide/Thionine and Nano-Ruthenium Oxide/Celestine Blue
The present study describes the fabrication of a sensitive amperometric sensor for the determination of persulfate. The immobilization surface was prepared by modifying a glassy carbon (GC) electrode with a nanocomposite containing ruthenium oxide (RuOx) nanoparticles and thionine (TH) or celestin blue (CB). The modified electrodes indicated excellent electrocatalytic activity toward persulfate reduction at a potential of +0.1 V. The proposed sensor showed detection limits of 1.46 mM for the GC/RuOx/TH modified electrode and 2.64 mM for the GC/RuOx/CB modified electrode. The sensitivities were obtained as 3 nAmM1 at a concentration range of 10 mM to 11 mM for the GC/RuOx/TH modified electrode and 1 nAmM1 at a concentration range of 10 mM to 6 mM for the GC/RuOx/CB modified electrodes
Novel electrochemical sensor based on graphene quantumdots/riboflavin nanocomposite for the detection of persulfate
Abstract
Novel electrochemical sensor based on graphene quantumdots/riboflavin nanocomposite for the detection of persulfate
tA novel and sensitive electrochemical sensor based on graphene quantum dots/riboflavin modified glassycarbon (GC/GQDs/RF) electrode was constructed and utilized to determine persulfate (S2O82−). GQDswere expected to have the significant properties of graphene materials as well as new functions result-ing from their quantum confinement and edge effects. The UV–vis, photoluminescence spectroscopy andtransmission electron microscopy (TEM) techniques were used for characterizing the GQDs. The modifiedelectrode showed stable and well-defined redox couples at a wide pH range (1–10), with surface con-fined characteristics. The electron transfer coefficient (˛) and the heterogeneous electron transfer rateconstant (ks) for redox reaction of RF were found to be 0.52 and 6.59 s−1, respectively. The GC/GQDs/RFelectrode exhibits an excellent electrocatalytic activity for a S2O82−reduction, with a measured kcatof∼4.8 × 103M−1s−1. This catalytic reduction allows an amperometric detection of S2O82−at a potential of−0.1 V with detection limit of 0.2 M, concentration calibration range of 1.0 M to 1 mM and sensitivityof 4.7 nA M−1, respectively.
Electrochemical Preparation and Thermal Characterization of Copper Sulfide Nanoparticles
Abstract
Electrochemical Preparation and Thermal Characterization of Copper Sulfide Nanoparticles
CuS nanoparticles in different sizes and shapes were synthesized by electrolysis of a copper plate as anode in sodium sulfide aqueous solutions. The results revealed that size and shape of the product could be tuned by the reaction parameters including electrolysis voltage and sulfide ion concentration as reactant. The results showed that the size of CuS nanoparticles decreased with increasing electrolysis voltage from 2 to 13 V. Meanwhile, the size and shape of the prepared CuS nanoparticles were found to be dependent on the concentration of sulfide solution used. Also, the results of characterization of the prepared CuS nanoparticles were reported.
Electrochemical detection of butylated hydroxyanisole based on glassy carbon electrode modified by iridium oxide nanoparticles
Abstract
Electrochemical detection of butylated hydroxyanisole based on glassy carbon electrode modified by iridium oxide nanoparticles
The present study describes a new approach for the investigation of electrocatalytic oxidation of butylated hydroxyanisole (BHA) by using a glassy carbon electrode modified by iridium oxide nanoparticles (GCE/IrOxNPs). IrOxNPs are grown on a GCE by electrodepositing method. It was observed that GCE/IrOxNPs showed a significant electrocatalytic activity toward BHA oxidation. Various experimental parameters influencing the electrochemical behavior of the modified electrode were optimized by varying the scan rates and pH. Cyclic voltammetric studies showed that the catalytic peak current of GCE/IrOxNPs was amplified approximately to 5 times in comparison with the bare GCE. The detection limit, sensitivity, and catalytic rate constant (kcat) of the modified electrode toward BHA were 100 nM, 113 nA lM1, and 1.1 104 M1 s1, respectively, at linear concentration range of up to 280 lM. The modified electrode showed a good electrochemical response in terms of sensitivity and stability.
Development of a highly selective voltammetric sensor for nanomolar detection of mercury ions using glassy carbon electrode modified with a novel ion imprinted polymeric nanobeads and multi-wall carbon nanotubes
Abstract
Development of a highly selective voltammetric sensor for nanomolar detection of mercury ions using glassy carbon electrode modified with a novel ion imprinted polymeric nanobeads and multi-wall carbon nanotubes
This work reports a voltammetric sensor for selective recognition and sensitive determination of mercury ions using glassy carbon (GC) electrode modified with a novel ion imprinted polymeric nanobeads (IIP) and multi-wall carbon nanotubes (MWCNTs). The ion imprinted polymers were prepared by dissolving the certain amount of mercury chloride and 5,10,15,20-tetrakis(3-hydroxyphenyl) porphyrin, in the presence of methacrylic acid and ethyleneglycol-dimethacrylate, using 2,2-azobisisobutyronitrile as initiator. The differential pulse anodic stripping voltammetric technique was employed to investigate the performance of the GC–IIP–MWCNTs modified electrode for determination of hazardous mercury ions. The designed modified electrode was shown a linear response in the range of 1 108–7.0 104M of Hg2+ ion with a detection limit of 5.0 nM and sensitivity 4483.3 nA lM1. It was found that the peak currents of the modified electrode for Hg2+ ions were at maximum value in acetate buffer. The preconcentration potential and accumulation time were optimized to be 1.0 V and 100 s, respectively.
Amperometric determination of sulfide ion by glassy carbon electrode modified with multiwall carbon nanotubes and copper (II) phenanthroline complex
Abstract
Amperometric determination of sulfide ion by glassy carbon electrode modified with multiwall carbon nanotubes and copper (II) phenanthroline complex
Amperometric determination of sulfide ion by glassy carbon electrode modified with multiwall carbon nanotubes and copper (II) phenanthroline complex
Sensitive quantification of trace zinc in water samples by adsorptive stripping voltammetry
Abstract
Sensitive quantification of trace zinc in water samples by adsorptive stripping voltammetry
A simple and sensitive adsorptive stripping voltammetry method was developed for determination of Zn using N-nitrozo-N-phenylhydroxylamine (cupferron) as a selective complexing agent. This complex absorbed on the hanging mercury drop electrode and created a sensitive peak current. The peak current and concentration of zinc accorded with a linear relationship in the range of 0.85–320 ng mL1. The influence of pH and the nature of supporting electrolytes, concentration of ligand, preconcentration time and applied potential were investigated. The relative standard deviation at a concentration level of 50 ng mL1 was 1.8%. The method was applied to the determination of zinc in city, river and mineral water samples, with satisfactory results.
Amperometric detection of hydrogen peroxide at nano-rutheniumoxide/riboflavin nanocomposite-modified glassy carbon electrodes
Abstract
Amperometric detection of hydrogen peroxide at nano-rutheniumoxide/riboflavin nanocomposite-modified glassy carbon electrodes
tA simple and sensitive electrochemical sensor based on nano-ruthenium oxide/riboflavin modified glassycarbon (GC/RuOx/RF) electrode was constructed and utilized to determine H2O2. By immersing theGC/RuOx modified electrode into RF solution for a short period of time (5–70 s), a thin film of the proposedmolecule was immobilized onto the electrode surface. The modified electrode showed stable and a well-defined redox couples at a wide pH range (1–10), with surface confined characteristics. Experimentalresults revealed that RF was adsorbed on the surface of RuOx nanoparticles (NPs) and in comparison tousual methods for the immobilization of RF, such as electropolymerization, the electrochemical reversibil-ity and stability of this modified electrode has been improved. The heterogeneous electron transfer rateconstant (ks) and the surface coverage of immobilized RF on the GC/RuOx electrode was obtained as16.8 s−1and 2.2 × 10−11mol cm−2, respectively. The electrocatalytic activity of the modified electrodetoward hydrogen peroxide reduction was investigated and it was found that the GC/RuOx/RF electrodeillustrates electrocatalytic activity toward H2O2reduction at reduced overpotential. The catalytic rateconstant (kcat) of the modified electrode toward H2O2is 9.1 × 103M−1s−1. This biosensor shows excel-lent sensitivity toward H2O2in buffer solution (pH 7) with a wide linear range from 0.15 M to 3 mM.The detection limit and sensitivity are 150 nM and 35 nA M−1respectively. Furthermore, the fabricatedH2O2chemical sensor exhibited excellent stability, remarkable catalytic activity and reproducibility.
Highly selective detection of dopamine in the presence of ascorbic acid and uric acid using thioglycolic acid capped CdTe quantum dots modified electrode
Abstract
Highly selective detection of dopamine in the presence of ascorbic acid and uric acid using thioglycolic acid capped CdTe quantum dots modified electrode
In this work, cadmium telluride (CdTe) quantum dots (QDs) have been successfully applied for construction of a novel chemically modified electrode for determination of dopamine (DA) in the presence of ascorbic acid (AA) and uric acid (UA). The small CdTe QDs were synthesized by using a wet chemical routes in the presence of thioglycolic acid (TGA), as capping agent at pH 9.5, having particle diameters of 1–3 nm. The synthesized QDs were immobilized on the surface of gold disk electrode by self assembly method in dark conditions for 30 h and electrochemically characterized. The modified CdTe QDs-based electrode afforded the simultaneous detection of these three compounds with wide peak separations, which allowed the interferences to be masked with applied potential. Using a potential window of 0–350 mV, where only dopamine was electroactive, a detection limit of 8.27 109 M and 1.30 109 M were calculated from square wave voltammetry and amperometry, respectively.
Hydrogen peroxide sensor based on riboflavin immobilized at the nickel oxide nanoparticle-modified glassy carbon electrode
Abstract
Hydrogen peroxide sensor based on riboflavin immobilized at the nickel oxide nanoparticle-modified glassy carbon electrode
A simple and sensitive electrochemical sensor based on nickel oxide nanoparticles/riboflavin-modified glassy carbon (NiONPs/RF/GC) electrode was constructed and utilized to determine H2O2. By immersing the NiONPs/ GC-modified electrode into riboflavin (RF) solution for a short period of time (5–300 s), a thin film of the proposed molecule was immobilized onto the electrode surface. The modified electrode showed stable and a well-defined redox couples at a wide pH range (2–10), with surface-confined characteristics. Experimental results revealed that RF was adsorbed on the surface of NiONPs, and in comparison with usual methods for the immobilization of RF, such as electropolymerization, the electrochemical reversibility and stability of this modified electrode has been improved. The surface coverage and heterogeneous electron transfer rate constants (ks) of RF immobilized on a NiOx–GC electrode were approximately 4.83 9 10-11 mol cm-2, 54 s-1, respectively. The sensor exhibits a powerful electrocatalytic activity for the reduction of H2O2. The detection limit, sensitivity and catalytic rate constant (kcat) of the modified electrode toward H2O2 were 85 nM, 24 nA lM-1 and 7.3 (±0.2) 9 103 M-1 s-1, respectively, at linear concentration rang up to 3.0 mM. The reproducibility of the sensor was investigated in 10 lM H2O2 by amperometry, the value obtained being 2.5 % (n = 10). Furthermore, the fabricated H2O2 chemical sensor exhibited an excellent stability, remarkable catalytic activity and reproducibility.
Ion imprinted polymeric nanoparticles for selective separation and sensitive determination of zinc ions in different matrices
Abstract
Ion imprinted polymeric nanoparticles for selective separation and sensitive determination of zinc ions in different matrices
Preparation of Zn2+ ion-imprinted polymer (Zn-IIP) nanoparticles is presented in this report. The Zn-IIP nanoparticles are prepared by dissolving stoichiometric amounts of zinc nitrate and selected chelating ligand, 3,5,7,20,40-pentahydroxyflavone, in 15 mL ethanol-acetonitrile (2:1; v/v) mixture as a porogen solvent in the presence of ethylene glycol-dimethacrylate (EGDMA) as cross-linking, methacrylic acid (MAA) as functional monomer, and 2,2-azobisisobutyronitrile (AIBN) as initiator. After polymerization, Cavities in the polymer particles corresponding to the Zn2+ ions were created by leaching the polymer in HCl aqueous solution. The synthesized IIPs were characterized by scanning electron microscopy, Xray diffraction, Fourier transform infrared spectroscopy, fluorescence spectroscopy and thermal analysis techniques. Also, the pH range for rebinding of Zn2+ ion on the IIP and equilibrium binding time were optimized, using flame atomic absorption spectrometry. In selectivity study, it was found that imprinting results increased affinity of the material toward Zn2+ ion over other competitor metal ions with the same charge and close ionic radius. The prepared IIPs were repeatedly used and regenerated for six times without any significant decrease in polymer binding affinities. Finally, the prepared sorbent was successfully applied to the selective recognition and determination of zinc ion in different real samples.
Thin film formation of platinum nanoparticles at oil– water interface, using organoplatinum(II) complexes, suitable for electro-oxidation of methanol
Abstract
Thin film formation of platinum nanoparticles at oil– water interface, using organoplatinum(II) complexes, suitable for electro-oxidation of methanol
A simple and effective strategy is presented to integrate individual platinum nanoparticles (NPs) into macroscopic thin films based on the reduction of organoplatinum(II) complexes [PtCl2(cod)] 1a, [PtI2(cod)] 1b (cod = 1,5-cyclooctadiene) and cis-[Pt(p-MeC6H4)2(SMe2)2] 2, at the toluene–water interface in the absence of stabilizer. Structure and morphology of the platinum NPs were characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) techniques. Finally, platinum thin films were deposited on glassy carbon electrode and their electro-oxidation was investigated in the methanol oxidation reaction. Pt NPs thin films showed highly improved electrocatalytical activity toward methanol oxidation as compared with commercial platinum catalysts. The present method provides a facile and low-cost strategy toward the synthesis of different electrocatalysts of noble metals for application in fuel cells.
Covalent attachment of thionine onto gold electrode modified with cadmium sulfide nanoparticles: Improvement of electrocatalytic and photelectrocatalytic reduction of hydrogen peroxide
Abstract
Covalent attachment of thionine onto gold electrode modified with cadmium sulfide nanoparticles: Improvement of electrocatalytic and photelectrocatalytic reduction of hydrogen peroxide
A newly developed strategy based on gold (Au) electrode modified with cadmium sulfide nanoparticles (CdSnp) and thionine (Th) was proposed toward electrocatalytic and photoelectrocatalytic hydrogen peroxide (H2O2) reduction. At first, a thin film of CdS nanoparticles was electrodeposited onto Au electrode. Then, the CdS/Au electrode was modified with mercaptoacetic acid (MAA), which not only acts as a stabilizing agent to prevent the chalcogenide CdS nanocrystals from aggregation but also as a linker for subsequent attachment of Th onto the CdS nanoparticles. The effective covalent immobilization of Th was achieved through amide bond formation reaction between NH2 groups of Th and COOH groups of MAA, using dicyclohexylcarbodiimide (DCC) as condensation agent. The Au/CdS/Th modified electrode showed a well-defined redox couple with surface confined characteristics at wide pH range (2–12). The heterogeneous electron transfer rate constant (ks) and the surface coverage of immobilized Th on the modified electrode was obtained as 0.12 s−1 and 4.35 × 10−9 mole cm−2, respectively. The electrocatalytic activity and stability of the modified electrode toward hydrogen peroxide reduction was investigated and it was found that the Au/CdS/Th electrode illustrates excellent electrocatalytic activity toward H2O2 reduction at reduced overpotential. The detection limit, sensitivity and catalytic rate constant (kcat) of the modified electrode toward H2O2 were 55 nM, 3.4 A M−1 cm−2 and 3.75 (±0.1) ×103M−1 s−1, respectively, at linear concentration range up to 10 mM. Upon light irradiation, about two-fold improvements were attained in sensitivity and detection limit of the modified electrode toward H2O2 electrocatalytic determination.
Applying Taguchi robust design to the optimization of synthesis of barium carbonate nanorods via direct precipitation
Abstract
Applying Taguchi robust design to the optimization of synthesis of barium carbonate nanorods via direct precipitation
An orthogonal array design was employed as a novel chemometric method for the optimization of operational conditions for synthesis of barium carbonate nanorods. BaCO3 nanorods were synthesied via a simple, controllable, and fast direct precipitation method via addition of barium ion solution to the bicarbonate reagent. Effects of various experimental conditions on the width of BaCO3 rods were quantitavely evaluated via analysis of variance. The obtained results revealed that barium carbonate nanorods can be synthesized by controlling significant parameters including barium and bicarbonate concentrations and temperature of the reactor. Based on the results of analysis of variance, 0.01 mol/L concentrations of both barium nitrate and sodium bicarbonate and a temperature of 20 ◦C found as optimum conditions for the effective preparation of barrium carbonate nanorods of 89 ± 10 nm width. The BaCO3 nanorods, prepared under optimum conditions, were characterized by various techniques including X-ray diffraction, scanning electron microscopy, UV–vis spectrophotometery, FT-IR spectroscopy and thermal analysis methods. Meanwhile, sub-micron rods of BaCO3 were prepared by the aid of bioactive eggshell membrane as template. The results showed that BaCO3 sub-micron rods prepared by this technique possess an average diameter of about 200 nm.
Development of a highly selective voltammetric sensor for nanomolar detection of mercury ions using glassy carbon electrode modified with a novel ion imprinted polymeric nanobeads and multi-wall carbon nanotubes
Abstract
Development of a highly selective voltammetric sensor for nanomolar detection of mercury ions using glassy carbon electrode modified with a novel ion imprinted polymeric nanobeads and multi-wall carbon nanotubes
This work reports a voltammetric sensor for selective recognition and sensitive determination of mercury ions using glassy carbon (GC) electrode modified with a novel ion imprinted polymeric nanobeads (IIP) and multi-wall carbon nanotubes (MWCNTs). The ion imprinted polymers were prepared by dissolving the certain amount of mercury chloride and 5,10,15,20-tetrakis(3-hydroxyphenyl) porphyrin, in the presence of methacrylic acid and ethyleneglycol-dimethacrylate, using 2,2-azobisisobutyronitrile as initiator. The differential pulse anodic stripping voltammetric technique was employed to investigate the performance of the GC–IIP–MWCNTs modified electrode for determination of hazardous mercury ions. The designed modified electrode was shown a linear response in the range of 1 108–7.0 104M of Hg2+ ion with a detection limit of 5.0 nM and sensitivity 4483.3 nA lM1. It was found that the peak currents of the modified electrode for Hg2+ ions were at maximum value in acetate buffer. The preconcentration potential and accumulation time were optimized to be 1.0 V and 100 s, respectively
Synthesis, spectroscopy, electrochemistry and thermogravimetry of copper(II) tridentate Schiff base complexes, theoretical study of the structures of compounds and kinetic study of the tautomerism reactions by ab initio calculations
Abstract
Synthesis, spectroscopy, electrochemistry and thermogravimetry of copper(II) tridentate Schiff base complexes, theoretical study of the structures of compounds and kinetic study of the tautomerism reactions by ab initio calculations
Attempts to spectroscopic and structural study of copper complexes, some Cu(II) Schiff base complexes were synthesized and characterized by means of electronic, IR, 1HNMR spectra and elemental analysis. The thermal analyses of the complexes were investigated and the first order kinetic parameters were derived for them. The cyclic voltammetric studies in acetonitrile were proposed a monomeric structure for complexes. The structures of compounds were determined by ab initio calculations. In the solid state, the ligands exist as keto-amine/enol-imine tautomeric forms with an intramolecular hydrogen bond (NAH O) between amine and carbonyl group. The kinetic studies of the tautomerism and equilibrium constant of the reactions were calculated using transition state theory. The optimized molecular geometry and atomic charges were calculated using MP2 method with 6-31G(d) basis set for H, C, N and O atoms and LANL2DZ for the Cu atom. The results suggested that, in the complexes, Cu(II) ion is in pseudo square-planar NO3 coordination geometry. Also the bond lengths and angles were studied and compared.
Highly Sensitive and Selective Amperometric Detection of Periodate at Glassy Carbon Electrode Modified with a Cyclometalated Iridium(III) Complex and Single-Wall Carbon Nanotubes
Abstract
Highly Sensitive and Selective Amperometric Detection of Periodate at Glassy Carbon Electrode Modified with a Cyclometalated Iridium(III) Complex and Single-Wall Carbon Nanotubes
Single-wall carbon nanotubes (SWCNTs) were used as an immobilization matrix to incorporate [Ir(ppy)2(phen-dione)](PF6) complex onto a glassy carbon electrode for the study of electrocatalytic reduction of periodate ion. Detailed preliminary electrochemical data for the Ir(III)-complex in acetonitrile solution and for the modified GCE/SWCNTs/[Ir(ppy)2(phen-dione)](PF6)/CGE are presented. The modified electrode was applied to selective amperometric detection of periodate through its electrocatalytic reduction to iodide at 0.200 V and pH 2.0. The use of amperometry resulted in two calibration plots over the concentration ranges of 1-20 μM and 20-450 μM, with a detection limit of 0.6 μM and sensitivity of 198 nAμM-1.
Electrochemical synthesis and characterization of zinc oxalate nanoparticles
Abstract
Electrochemical synthesis and characterization of zinc oxalate nanoparticles
A rapid, clean and simple electrodeposition method was designed for the synthesis of zinc oxalate nanoparticles. Zinc oxalate nanoparticles in different size and shapes were electrodeposited by electrolysis of a zinc plate anode in sodium oxalate aqueous solutions. It was found that the size and shape of the product could be tuned by electrolysis voltage, oxalate ion concentration, and stirring rate of electrolyte solution. A Taguchi orthogonal array design was designed to identify the optimal experimental conditions. The morphological characterization of the product was carried out by scanning electron microscopy. UV–vis and FT-IR spectroscopies were also used to characterize the electrodeposited nanoparticles. The TG–DTA studies of the nanoparticles indicated that the main thermal degradation occurs in two steps over a temperature range of 350–430 8C. In contrast to the existing methods, the present study describes a process which can be easily scaled up for the production of nano-sized zinc oxalate powder.
Synthesis, spectroscopy, electrochemistry and thermal study of vanadyl tridentate Schiff base complexes: theoretical study of the structures of compounds by ab initio calculations
Abstract
Synthesis, spectroscopy, electrochemistry and thermal study of vanadyl tridentate Schiff base complexes: theoretical study of the structures of compounds by ab initio calculations
The VO(IV) complexes of tridentate ONN Schiff ligands were synthesized and characterized by IR, UV–Vis and elemental analysis. The electrochemical properties of the vanadyl complexes were investigated by cyclic voltammetry. A good correlation was observed between the oxidation potentials and the electron-withdrawing character of the substituents on the Schiff base ligands, showing the following trend: MeO\H\Br\NO2. The thermogravimetry (TG) and differential thermoanalysis (DTA) of the VO(IV) complexes were carried out in the range of 20–700 C. The VOL1(OH2) and VOL2(OH2) decomposed in three steps, whereas the VOL3(OH2) and VOL4(OH2) complexes decomposed in two steps. The thermal decomposition of these complexes is closely related to the nature of the Schiff base ligands and proceeds via first-order kinetics. The structures of compounds were determined by ab initio calculations. The optimized molecular geometry and atomic charges were calculated using MP2 method with 6-31G(d) basis. The results suggested that, in the complexes, V(IV) ion is in square-pyramid N2O3 coordination geometry. Also the bond lengths and angles were studied and compared.
Amprometric detection of Glycine, L-Serine, and L-Alanine using glassy carbon electrode modified by NiO nanoparticles
Abstract
Amprometric detection of Glycine, L-Serine, and L-Alanine using glassy carbon electrode modified by NiO nanoparticles
Glassy carbon electrode modified with nickel oxide nanoparticles has been used to investigate the electrochemical oxidation of Glycine, L-Serine, and L-Alanine in an alkaloid solution. The electrochemical behavior of the modified electrode was characterized by cyclic voltammetry in detail. The electrocatalytic behavior is further exploited as a sensitive detection scheme for the above amino acids by hydrodynamic amperometry. Under optimized conditions, the calibration curves are linear in the concentration ranges of 1–200 lM for Glycine, 1–400 lM for L-Serine, and 30–200 lM for L-Alanine, respectively. The respective detection limit (S/N = 3) and sensitivity are 0.9 lM and 24.3 nA lM-1 for Glycine, 0.85 lM and 12.4 nA lM-1 for L-Serine, and 29.67 lM and 0.4 nA lM-1 for L-Alanine. The prepared electrode exhibits a satisfactory stability and long life-time, while it is stored at ambient conditions.
Room temperature synthesis and characterization of ultralong Cd(OH)2 nanowires: a simple and template-free chemical route
Abstract
Room temperature synthesis and characterization of ultralong Cd(OH)2 nanowires: a simple and template-free chemical route
Ultralong Cd(OH)2 nanowires were fabricated in high yield by a convenient chemical method using alkali medium at room temperature without using any templates. The preparation conditions induce a unilateral growth of nanowires, despite the absence of any template. The length of the nanowires reached several hundreds of micrometers, giving an aspect ratio of a few thousands. The X-ray diffraction shows that the Cd(OH)2 nanostructures crystallized in the wurtzite structure without any special orientation. The photoluminescence spectrum of Cd(OH)2 nanostructures appears as two emission bands: one related to green emission at 475–510 nm, and the other related to deep level emission at 510–540 nm. Also the formation mechanisms of the nanowires are presented. The growth mechanism involves the irreversible and specifically oriented selfassembly of primary nanocrystals and results in the formation of the nanowires.
Thermal Behavior and Non-Isothermal Kinetic Studies on Titanium Hydride–Fueled Binary Pyrotechnic Compositions
Abstract
Thermal Behavior and Non-Isothermal Kinetic Studies on Titanium Hydride–Fueled Binary Pyrotechnic Compositions
This study describes thermochemical properties and ignition characteristics of pyrotechnic compositions consisting of TiH2þKClO3, TiH2þKClO4, and TiH2þBa(NO3)2, where titanium hydride is used as fuel and KClO3, KClO4, and Ba(NO3)2 act as oxidants. Differential thermal analysis (DTA) and thermogravimetry (TG) techniques have been employed to elucidate the reaction process of these pyrotechnic systems. TG/DTA analysis of pure titanium hydride indicates that this compound decomposes at 535 C. By replacing KClO3 with KClO4 as oxidizer in a titanium hydride–fueled mixture, the sensitivity of the mixture decreases. A TiH2þKClO3 pyrotechnic mixture has a fusion temperature around 358 C and ignition temperature around 472 C. A TiH2þKClO4 pyrotechnic system decomposes at 541.5 C. However, replacing KClO4 with Ba(NO3)2 in this mixture, increases the ignition temperature of the mixture by at least 30 C to570 C, which is a safe temperature for preventing activation of the mixture by accidental factors such as static electricity. The apparent activation energy (E), DG#, DH#, and DS# of the combustion processes were obtained from the DSC experiments. Thermokinetic data shows that the relative reactivity of these mixtures decrease in the following order: TiH2þKClO3> TiH2þKClO4>TiH2þBa(NO3)2.
Synthesis, spectroscopy, electrochemistry and thermal study of uranyl N3O2 Schiff base complexes
Abstract
Synthesis, spectroscopy, electrochemistry and thermal study of uranyl N3O2 Schiff base complexes
The new [UO2L(CH3OH)] [where L = bis (salicylaldehyde)2,6-diiminopyridine (L1), bis(5-methoxysalicylaldehyde) 2,6-diiminopyridine (L2), bis(5-bromosalicylaldehyde) 2,6-diiminopyridine (L3), bis(5-nitrosalicylaldehyde) 2,6-diiminopyridine (L4)] complexes were synthesized and characterized by IR, UV–vis and elemental analysis. Methanol solvent is coordinated to uranyl complexes. The electrochemical properties of the uranyl complexes were investigated by cyclic voltammetry in DMF solvent. Thermogravimetry and differential thermoanalysis of the uranyl complexes were carried out in the range of 20–700 C. The UO2L4 complex was decomposed in two and the others were decomposed in three stages. Up to 85 C, the coordinated solvent was released then the Schiff base ligands were decomposed in one or two steps. Decomposition of synthesized complexes is related to the Schiff base characteristics. The thermal decomposition reaction is first order for the studied complexes.
Synthesis, spectroscopy, electrochemistry and thermal study of vanadyl tridentate Schiff base complexes
Abstract
Synthesis, spectroscopy, electrochemistry and thermal study of vanadyl tridentate Schiff base complexes
The VO(IV) complexes of tridentate ONO Schiff ligands were synthesised and characterized by IR, UV–vis and elemental analysis. The electrochemical properties of the vanadyl complexes were investigated by cyclic voltammetry. A good correlation was observed between the oxidation potentials and the electron withdrawing character of the substituents on the Schiff base ligands, showing the following trend: MeO < H < Br < NO2 and H < Cl. The thermogravimetry (TG) and differential thermoanalysis (DTA) of the VO(IV) complexes were carried out in the range of 20–700 ◦C. The VOL1(OH2) decomposed in two steps whereas the remaining six complexes decomposed in three steps. The thermal decomposition of these complexes is closely related to the nature of the Schiff base ligands and proceeds via first order kinetics.
Synthesis, Characterization and Size Dependent Energy Band Gap of Binary CdSe Quantum Dot and Its Nanoparticle Film
Abstract
Synthesis, Characterization and Size Dependent Energy Band Gap of Binary CdSe Quantum Dot and Its Nanoparticle Film
Nanocrystals provide a confinement effect for nanoscale engineering. In this work the cadmium selenide quantum dot and its nanoparticle films have been deposited by chemical bath deposition method (CBD). Effects of deposition time, pH and annealing operation on the optical and structural of CdSe nanoparticle film were studied. The energy band gap, structure and morphology of the samples are investigated by X-ray diffraction (XRD), UV-Vis spectrometer and scanning electron microscope (SEM). It was found that the optical band gap, nanoparticle size and thin film configuration are changed by varying pH, deposition time and annealing operation.
Synthesis, spectroscopy, electrochemistry and thermal study of vanadyl unsymmetrical Schiff base complexes
Abstract
Synthesis, spectroscopy, electrochemistry and thermal study of vanadyl unsymmetrical Schiff base complexes
The new tetradentate unsymmetrical N2O2 Schiff base ligands and VO(IV) complexes were synthesised and characterized by using IR, UV–Vis and elemental analysis. The electrochemical properties of the vanadyl complexes were investigated by means of cyclic voltammetry. The oxidation potentials are increased by increasing the electron-withdrawing properties of functional groups of the Schiff base ligands according to the trend of MeO < H < Br < NO2. The thermogravimetry (TG) and differential thermoanalysis (DTA) of the VO(IV) complexes were carried out in the range of 20–700 C. The complexes were decomposed in two stages. Also decomposition of synthesised complexes is related to the Schiff base characteristics. The thermal decomposition of the studied reactions was first order.
Synthesis, spectroscopy, electrochemistry and thermal study of Ni(II) and Cu(II) unsymmetrical N2O2 Schiff base complexes
Abstract
Synthesis, spectroscopy, electrochemistry and thermal study of Ni(II) and Cu(II) unsymmetrical N2O2 Schiff base complexes
The new tetradentate unsymmetrical N2O2 Schiff base ligands, Ni(II) and Cu(II) complexes were synthesised and chracterized by IR, UV–vis, 1H NMR and elemental analysis. The electrochemical properties of the Ni(II) complexes were investigated. The thermogravimetry of the Ni(II) and Cu(II) complexes were carried out in the range of 20–700 ◦C. Decomposition of synthesised complexes is related to the Schiff base characteristics
Picomolar Detection of Insulin at Renewable Nickel Powder-Doped Carbon Composite Electrode
Abstract
Picomolar Detection of Insulin at Renewable Nickel Powder-Doped Carbon Composite Electrode
A sol-gel technique was used for fabrication of a renewable carbon composite electrode (CCE) modified with nickel powder. This modified electrode shows excellent catalytic activity for the oxidation of insulin in alkaline solutions. The nickel powder was then oxidized to form a nickel oxide film electrode, which was used as an amperometric detector for hydrodynamic amperometry and flow injection analysis of insulin. It was found that the calibration curve was linear up to 30 íM with a detection limit of 40 pM under the optimized conditions for hydrodynamic amperometry using a rotating disk modified CCE. Flow injection amperometric determination of insulin at this modified electrode yielded a calibration curve with the following characteristics; linear dynamic range of 15-1000 pM, sensitivity of 8659.23 pA pM-1 cm-2, and detection limit of 2 pM. This electrode shows many advantages as an insulin sensor such as simple preparation method without using any specific electron-transfer mediator or specific reagent, high sensitivity, excellent catalytic activity, short response time, long-term stability, and remarkable antifouling property toward insulin and its oxidation product. Sensitivity, detection limit, and antifouling properties of this insulin sensor are better than all of the reports in the literature. Additionally, it is promising for monitoring insulin in chromatographic effluents.
Electrocatalytic Oxidation of Sulfur Containing Amino Acids at Renewable Ni-Powder Doped Carbon Ceramic Electrode: Application to Amperometric Detection l-Cystine, l-Cysteine and l-Methionine
Abstract
Electrocatalytic Oxidation of Sulfur Containing Amino Acids at Renewable Ni-Powder Doped Carbon Ceramic Electrode: Application to Amperometric Detection l-Cystine, l-Cysteine and l-Methionine
A sol-gel technique was used here to prepare a renewable carbon ceramic electrode modified with nickel powder. Cyclic voltammograms of the resulting modified electrode show stable and a well defined redox couple due to Ni(II)/ Ni(III) system with surface confined characteristics. The modified electrode shows excellent catalytic activity toward l-cystine, l-cysteine and l-methionine oxidation at reduced overpotential in alkaline solutions. In addition the antifouling properties at the modified electrode toward the above analytes and their oxidation products increases the reproducibility of results. l-cystine, l-cysteine and l-methionine were determined chronoamperometricaly at the surface of this modified electrode at pH range 9 – 13. Under the optimized conditions the calibration curves are linear in the concentration range 1 – 450 mM, 2 – 90 mM and 0.2 – 75 mM for l-cystine, l-methionine and l-cysteine determination, respectively. The detection limit and sensitivity were 0.64 mM, 3.8 nA/ mM for l-cystine, 2 mM, 5.6 nA/ mM for l-methionine and 0.2 mM and 8.1 nA/mM for l-cysteine. The advantageous of this modified electrode is high response, good stability and reproducibility, excellent catalytic activity for oxidation inert molecules at reduced overpotential and possibility of regeneration of the electrode surface by potential cycling for 5 minutes. Furthermore, the modified electrode has been prepared without using specific reagents. This sensor can be used as an amperometric detector for disulfides detection in chromatographic or flow systems.
Amperometric detection of insulin at renewable sol–gel derived carbon ceramic electrode modified with nickel powder and potassium octacyanomolybdate(IV)
Abstract
Amperometric detection of insulin at renewable sol–gel derived carbon ceramic electrode modified with nickel powder and potassium octacyanomolybdate(IV)
A renewable three-dimensional chemically modified carbon ceramic electrode (CCE) containing nickel powder and K4[Mo(CN)8] was constructed by sol–gel technique. The electrochemical properties and stability of modified electrode was evaluated by cyclic voltammetry in pH range 4–10. The redox couple of [Mo(CN)8] 4−/3− was shown both as a solute in electrolyte solution and as a component of a carbon based conducting composite electrode. The apparent electron transfer rate constant (ks) and transfer coefficient (α) were determined by cyclic voltammetry and they were about 17.1 and 0.57 s−1, respectively. The catalytic activity of the modified CCE toward insulin oxidation was investigated at pH range of 3–8 by cyclic votammetry. The modified electrode showed excellent electrocatalytic activity toward insulin electroxidation at physiological pH value. The modified electrode was used for insulin detection chronoamperometrically at pH 7. Under optimized condition in amperometry method, the concentration calibration range, detection limit and sensitivity were 0.5–500 nM, 0.45nM and 6140 nA/M, respectively. Flow injection amperometric determination of insulin at pH 7.4, at this modified electrode yielded a calibration curve with the following characteristics, linear dynamic range 100–500 pM; sensitivity 8.1 nA/nM and detection limit 40pM (based on S/N = 3). The inherent stability at wide pH range, high sensitivity, low detection limit, low cost and ease of preparation are of advantageous of this insulin sensor. This sensor indicates great promise for monitory insulin in chromatographic effluents.
Non-enzymatic glucose detection free of ascorbic acid interference using nickel powder and nafion sol–gel dispersed renewable carbon ceramic electrode
Abstract
Non-enzymatic glucose detection free of ascorbic acid interference using nickel powder and nafion sol–gel dispersed renewable carbon ceramic electrode
A new enzymeless glucose sensor has been fabricated by a nickel powder dispersed sol–gel derived ceramic graphite composite. The electrocatalytic oxidation of glucose in alkaline medium directly at nickel powder modified carbon ceramic electrode has been investigated. The modified electrode offer excellent electrocatalytic activity toward the glucose oxidation at low positive potential (0.45 V vs. Ag/AgCl, 3 M KCl). Glucose was determined chronoamperometrically at the surface of the modified electrode in pH 13. Under the optimized condition, the calibration curve is linear in the concentration range of 0.5–5000 lM. The detection limit (signal-to-noise 3) and sensitivity are 0.1 lM and 40 nA lM1, respectively. The glucose sensor can be renewed easily in a reproducible manner by a simple polishing step and it has a long operational lifetime and short response time t90% < 1 s. In addition, the fabrication of CCE with nafion and nickel powder was employed to eliminate the interference of ascorbic acid during the catalytic oxidation of glucose. The capability of the modified electrode for direct glucose quantification in human blood serum matrix is also discussed.
Micromolar determination of sulfur oxoanions and sulfide at a renewable sol–gel carbon ceramic electrode modified with nickel powder
Abstract
Micromolar determination of sulfur oxoanions and sulfide at a renewable sol–gel carbon ceramic electrode modified with nickel powder
The sol–gel technique was used to fabricate nickel powder carbon composite electrode (CCE). The nickel powder successfully used to deposit NiOx thin film on conductive carbon ceramic electrode for large surface area catalytic application. Repetitive cycling in potential range −0.2 to 1.0V was used to form of a thin nickel oxide film on the surface carbon composite electrode. The thin film exhibits an excellent electrocatalytic activity for oxidation of SO3 2−, S2O4 2−, S2O3 2−, S4O6 2− and S2− in alkaline pH range 10–14. Optimum pH values for detection of all sulfur derivatives is 13 and catalytic rate constants are in range 2.4×103–8.9×103M−1 s−1. The hydrodynamic amperometry at rotating modified CCE at constant potential versus reference electrode was used for detection of sulfur derivatives. Under optimized conditions the calibration plots are linear in the concentration range 10 M–15mM and detection limit 1.2–34 M and 0.53–7.58 nA/M (sensitivity) for electrode surface area 0.0314 cm2. The nickel powder doped modified carbon ceramic electrode shows good reproducibility, a short response time (2.0 s), remarkable long term stability, less expense, simplicity of preparation, good chemical and mechanical stability, and especially good surface renewability by simple mechanical polishing and repetitive potential cycling. This sensor can be used into the design of a simple and cheap chromatographic amperometry detector for analysis of sulfur derivatives.
A novel aptasensor based on gold nanorods/ZnS QDs-modified electrode for evaluation of streptomycin antibiotic
Abstract
A novel aptasensor based on gold nanorods/ZnS QDs-modified electrode for evaluation of streptomycin antibiotic
In this study, a simple and effective strategy was developed for specific detection of streptomycin (STR) antibiotic. At first, in this strategy, glassy carbon electrode (GCE) was covered by thiourea capped-ZnS QDs and gold nanorods (AuNRs) for the construction of a sensing interface for thiolated aptamer immobilization. Subsequently, the STR thiol-aptamer was covalently attached on the AuNRs/thiourea capped-ZnS QDs/GCE via Au–S bond formation. Morphology of the modified electrode was characterized via emission scanning electron microscopy (FE-SEM) technique. The proposed system showed good linearity ranging from 1 fg mL1 to 1.111 pg mL1 and 1.111 pg mL1 to 11.1111 ng mL1, with a detection limit of 0.35 fg mL1. Furthermore, this methodology was also applied to evaluate STR in milk and serum samples, indicating the feasibility of the application of aptasensor analysis for STR detection. The presented system, in presence of different interferences, indicated good selectivity in detecting the STR. Our study provides a facile and low-cost method for designing aptamer-based sensors toward the evaluation of other antibiotics if the specific aptamer is available.
تخریب فوتوکاتالیستی ماده رنگزاي آرسنازو ) III ( به وسیله نقاط کوانتومی گرافن تحت نور مرئی
چکیده
تخریب فوتوکاتالیستی ماده رنگزاي آرسنازو ) III ( به وسیله نقاط کوانتومی گرافن تحت نور مرئی
در این مطالعه از نقاط کوانتومی گرافن ) GQDs ( به عنوان نانو مواد جدید و بسیار کارآمد برای تخریب ماده رنگاای آرسنازو تحت نور مرئی استفاده شده است. سنتا نقاط کوانتومی گرافن با روش پیرولیا انجام شد و جهت بررسی GQDs تهیه شده، از میکروسکوا الکترونی عیوری ( TEM ( و طیف جذبی مرئی فرابنفش استفاده شد. تاثیر برخی عوامل تجربی مانند - pH محلول ماده رنگاا، زمان تماس، غلظت ماده رنگاا ی آرسنازو ) III ( و مقدار نقاط کوانتومی بر بازده تخریب ماده رنگاا مورد مطالعه قرار گرفته و بهینه گردید. در شرای بهینه شامل 4 pH= ، زمان تماس 121 دقیقه، غلظت ماده رنگاا 46 میلیگرم بر لیتر و در حضور 511 میکرولیتر GQDs ، بازده حذف ماده رنگاا بیش از 11 درصد مشاهده شد. به طور کلی، GQDs عملکرد خوبی در حذف ماده رنگاا داشت. در نهایت مدل سنیتیکی برای ماده رنگا ای آرسنازو ) III ( در حضور نقاط کوانتومی GQDs مورد بحث قرار گرفت و سازوکار احتمالی تخریب فوتوکاتالیستی تحت نور مرئی بررسی گردید.
تخریب فوتوکاتالیستی رنگ اریوکروم بلک T با استفاده از چارچوب فلز آلی TMU-16
چکیده
تخریب فوتوکاتالیستی رنگ اریوکروم بلک T با استفاده از چارچوب فلز آلی TMU-16
توسعه روش¬های تصفیه فاضلاب¬ها از موضوعات مهم زیست محیطی محسوب می¬شود. از میان روش¬های به کار برده شده فرایندهای اکسیداسیون پیشرفته (AOP) به دلیل تبدیل مواد آلاینده به موادی با سمیت کم¬تر و یا زیست تخریب¬پذیر، توجه بسیار زیادی را برای حذف گستره¬ی وسیعی از آلاینده¬های آلی، به خود جلب کرده¬اند. در این کار تخریب فوتوکاتالیستی رنگ اریوکروم بلک T تحت تابش نور UV در محلول¬های آبی با استفاده از چارچوب فلز-آلی TMU-16 به عنوان کاتالیستی ناهمگن مطالعه شد. چارچوب فلز-آلی TMU-16 تحت شرایط حلال¬حرارتی در دمای 115 درجه¬ی سانتی¬گراد سنتز و به کمک تکنیک¬های XRD و جذب و واجذب گاز (BET) شناسایی شد. اثر پارامترهای موثر بر میزان تخریب رنگ مانند pH، مقدار کاتالیست و غلظت اولیه رنگ مورد بررسی قرار گرفت. تخریب رنگ از مدل سینتیکی شبه درجه اول تبعیت می¬کند و سازوکار تخریب رنگ از مسیر رادیکال¬های هیدروکسیل و سوپراکسید پیش می¬رود. شکاف انرژی پایین (9/2 الکترون ولت) نشان می¬دهد که TMU-16 می¬تواند در حضور نور به عنوان کاتالیستی قدرتمند برای حذف رنگ¬ها و سایر آلاینده¬ها از محیط آبی استفاده شود.
Applicability of Aptamer-MIP Hybrid Receptor as a Sensing Interface in Fabrication of Ractopamine Aptasensor
Abstract
Applicability of Aptamer-MIP Hybrid Receptor as a Sensing Interface in Fabrication of Ractopamine Aptasensor
The importance of RAC tracking in human biofluids has boosted many demands for designing an ultrasensitive tool to determine the trace value of the RAC from clinical, judicial, and forensic centers. In this study, an electrochemical biodevice has developed for the highly selective detection of this illegal feed additive under a double recognition strategy of the aptamer (Apt) and molecular imprinting polymer (MIP) on a glassy carbon electrode (GCE). The sensing relies on this fact that both the MIP and Apt act synergistically to trap the RAC molecules. The sensing surface fabrication steps have been monitored by some electrochemical techniques such as electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV(. The charge transfer resistance (Rct) value of the redox probe as a representative of the biodevice response has increased linearly with the RAC concentration increasing in a dynamic range of 1 fM to 1.90 µM. The detection limit (LOD) value has been estimated to be 330 aM, lower than all of the reported methods in the RAC sensing. Furthermore, the practical feasibility of biodevice has been evaluated in some human blood serum and urine samples. This strategy offers some useful advantages in reliable detection of the RAC, which may help in the routine analysis, as mandated by regulatory agencies.
Development and investigation of a novel nanohybrid probe based on double recognition of Apt-MIP grafted on AuNPs@nano-C60 nanocomposite for TNT detection
Abstract
Development and investigation of a novel nanohybrid probe based on double recognition of Apt-MIP grafted on AuNPs@nano-C60 nanocomposite for TNT detection
ThisstudyintroducesanovelsyntheticreceptorsensorbasedonthecombinationofaptasensingandmolecularimprintingstrategiesfordesigningaighlysensitivesystemtoovercomesomeofthechallengedfacedbyconventionalmethodsinTNTsensing.Anamino-AptwithinherenttendencyforTNTwascomplexwithTNTmoleculepriortobeingcovalentattachmentontoaGCEsurfacewhichismodifiedwithanovelandacilenanocomposite(Au@nano-C60).Controlledelectropolimerysationofdopamine(DA)aroundtheApt[TNT]complexservedtobothentrapthecomplexandholdingtheApt,it’sbindingconformation,andtolocalisetheTNTbindingsitesatthesensorsurface.ByremovingofTNT,itisassumedthattheMIPcavitywouldactsynergisticallywiththeembeddedApttoformananohybridreceptor(Apt-MIP),indicatingrecognitionpropertiessuperiortothatofAptalone.BenefitingfromthedoublespecificmolecularrecognitionpropertyofMIPsandAptsalongwiththeinsitugenerationofAunanoparticlesontothesuraceoftheGCEmodifiedwithactivatedC60astheAu@nano-C60nanocompositeledtounbeatablesensingpropertiessuchaslowerLOD(3.33aM)andwiderlinearconcentrationrangeofTNT(0.01fMto1.5μM)incomparisontoanotherreportedmethodsintheliterature.ThesatisfactoryresultsindicatethattheproposedstrategycouldbeextendedtovariousdiagnosticallyreleventproteinsusingnotonlyAptsbutasootheraffinitymoleculessuchasaffimers,antibodyandpeptidefragments.
Development of a novel nanocomposite based on dendrimer-quantum dot (den-qd) bioconjugate for signal amplification in designing of an electrochemical aptasensor for the ultra-sensitive detection of cocaine
Abstract
Development of a novel nanocomposite based on dendrimer-quantum dot (den-qd) bioconjugate for signal amplification in designing of an electrochemical aptasensor for the ultra-sensitive detection of cocaine
A selective aptasensor was developed using the electrochemical transduction method for the ultrasensitive detection of cocaine. In this method, dendrimerquantum dot (Den-QD) bioconjugate was utilized as a specific nanocomposite to efficiently fabricate of the aptasensor. CdTe QD, which carries highly significant properties, was immobilized on the surface of a glassy carbon electrode (GCE), and polyamidoamine (PAMAM) Den was covalently attached to the carboxylterminated surface of the CdTe QDs. This clever combination of QD and Den provides a highly stable matrix for the increased loading of Apt as a cocaine molecular receptor via covalent attachment. The Apt was functionalized with AuNPs leading to the amplification of the electrochemical signal. In this study, upon the incubation of cocaine on the aptasensor surface, the peak current of the redox probe decreased due to the hindered electron transfer reaction on the sensing surface. It has shown that in optimal conditions, the proposed aptasensor can detect cocaine by electrochemical impedance spectroscopy (EIS) technique at a linear range (0.005-6 nM) and a capability of detection down to 1.6 pM. The excellent specificity of this sensing system is demonstrated by using some common analgesic drugs, and finally the proposed aptasensor was successfully used to measure cocaine in the human serum sample. The proposed methodology may hold great promise for the design of other aptasensors and immunosensors based on the use of the Den-QD bioconjugate as a nanocomposite with high performance.
Graphen Quantum Dots as a Novel Turn – Off Fluorescence Probe for Detection of Fenthion
Abstract
Graphen Quantum Dots as a Novel Turn – Off Fluorescence Probe for Detection of Fenthion
The aim of this report, detection and quantification fenthion with using from Graphen quantum Dots (GQDs) as carbon sources that is as a fluorescence (FL) probe.When Fenthion was added to a GQDs solution, efficiency quenched observed .quenching as a Result of the FL charge transfer which produced strong - bond formed between GQD and Fenthion. Using of fenthion in the concentration 2.5 to 250 ʽM earn a limit of detection 0.83ʽm. Linearity of response over fenthion was demonstrate r> 0.99.
fabrication of a selective impedimetric aptasensor for trace level detection of ractopamine base on a novel and efficient nanocomposite immobilized onto a GCE surface
Abstract
fabrication of a selective impedimetric aptasensor for trace level detection of ractopamine base on a novel and efficient nanocomposite immobilized onto a GCE surface
The importance of RAC tracking in human biofluids has boosted many demands for designing an ultrasensitive tool to determine the trace value of the RAC from clinical, judicial, and forensic centers. In this study, an electrochemical biodevice has developed for the highly selective detection of this
امکان سنجی استفاده از زبان الکترونیک در تعیین غلظت ترکیبات زعفران
چکیده
امکان سنجی استفاده از زبان الکترونیک در تعیین غلظت ترکیبات زعفران
زبان الکترونیک به عنوان یک رویکرد جدید در تحلیل مایعات کاربرد گستردهای در صنایع غذایی به ویژه کنترل کیفی و تشخیص اصالت محصول پیدا گیاهی چند ساله است که دارای پیاز کروی و پوشیده از یک غشای قهوهای رنگ میباشد. زعفران ،crodcus stativus کرده است. زعفران با نام علمی به جهت طعم، بو و رنگ خاصی که دارد به وفور در غذاها (به ویژه همراه برنج)، صنایع شرینی سازی، داروسازی و صنایع دیگر به مصرف میرسد. تاکنون برای درجهبندی زعفران، استفاده از یک روش تحلیلی توسعه نیافته است. با توجه به اهمیت چند جانبه زعفران و نقش بسیار مهم آن در صنعت غذا و دارو، لازم است تحقیقاتی در زمینه بررسی و کنترل کیفیت آن به منظور تعیین ترکیبات اصلی آن با استفاده از روشهای حسی نوین صورت گیرد. لذا در این مقاله قابلیت استفاده از سامانه مبتنی بر فناوری زبان الکترونیک جهت تعیین غلظت ترکیبات شیمیایی زعفران بررسی میشود.
preparation and characterization of polypyrrole/TiO2 nanocomposites in presence poly(vinyl pyrrolidone) (PVP)
چکیده
preparation and characterization of polypyrrole/TiO2 nanocomposites in presence poly(vinyl pyrrolidone) (PVP)
This work presents the synthesis of Polypyrrole/TiO2 nanocomposites. This nanocomposites were synthesized in aqueous media by polymerization of pyrrole using FeCl3 as an oxidant in the presence of poly(vinyl pyrrolidone) (PVP) as a surfactant and TiO2 nanoparticles. The PPy/TiO2 nanocomposites were characterized in terms of their particle size, morphology and chemical structure. X-ray diffraction (XRD) and fourier transform infrared (FTIR) spectra were used to characterized the structure of the obtained polypyrrole/TiO2 nanocomposites. Also the morphology of products was characterized by using scanning electron microscope (SEM). The results indicate that, the morphology and particle size of products are dependent on the presence of surfactant and metallic oxide
Effect Of Contact time And adsorbent dose On the removal Of zinc cation Using polypyrrole nanoparticles
چکیده
Effect Of Contact time And adsorbent dose On the removal Of zinc cation Using polypyrrole nanoparticles
One of the suitable methods for removing heavy metals from aqueous solution is using surface adsorption process. In this article, the effect of Polypyrrole (PPy) nanoparticles and also, the influence of contact time and adsorbent dose on the removal of zinc cation (Zn(II)) from aqueous solution were studied. The Polypyrrole nanoparticles were prepared using Hydroxyethylcellulose (HEC) as surfactant in the presence of Ferric chloride (FeCl3) as an oxidant in various solutions. The capability of separating Zn(II) ions was studied. The results indicate that the removal percentage is related to the Contact time and type and dose of adsorbent. Removal percentage was increased by increasing the adsorbent dose and contact time. The structure of obtained product was determined by FTIR spectroscopy.
مروری بر فناوری کاربردی فتوکاتالیست و نانوکاتنالیست
Abstract
مروری بر فناوری کاربردی فتوکاتالیست و نانوکاتنالیست
حسگرها و آپتاحسگرهای الکتروشیمیایی اجـزا، عملکـرد و کاربـرد (مروری بر جدیدترین فناوری¬های ساخت حسگرها و آپتاحسگرها)
Abstract
حسگرها و آپتاحسگرهای الکتروشیمیایی اجـزا، عملکـرد و کاربـرد (مروری بر جدیدترین فناوری¬های ساخت حسگرها و آپتاحسگرها)
شیمی ترکیبات گیاهی
چکیده
شیمی ترکیبات گیاهی
Metal-organic frameworks-derived Zn-Ni-P nanostructures as high performance electrode materials for electrochemical sensing
Abstract
Metal-organic frameworks-derived Zn-Ni-P nanostructures as high performance electrode materials for electrochemical sensing
The fabrication of hierarchical nanostructure based on metal–organic frameworks (MOFs)-derived transition-metal phosphides (TMPs) has become a hot topic in electrochemical sensor application owing to its unique properties. Herein, a scalable and facile strategy was proposed to prepare MOF-derived bimetallic Zn-Ni-P nanostructures. The material characterization showed that MOFs-derived Zn-Ni-P has flower-like structure that built from small 2D nanosheets. The MOFs-derived Zn-Ni-P was prepared via a facile phosphorization of Zn-Ni-MOF precursor in N2 atmosphere. This MOF-derived TMPs electrode materials offer excellent electrocatalytic activity toward isoprenaline (IPN) oxidation. In addition, the electrode shows wide two linear range (0.2 µM −5 mM and 5 mM-14 mM), short response time (<1s), low detection limit (0.06 µM), good sensitivity (66.748 μA mM−1), desirable repeatability and reproducibility (RSD < 3.5%), and capability for measuring IPN in real sample, which are comparable or better than most reported works for measuring IPN. This improvement can be due to the synergistic effects of multiple catalytic centers, high surface area, facilitated mass, and electron transfer.
A new method for electrochemical determination of Hippuric acid based on molecularly imprinted copolymer
Abstract
A new method for electrochemical determination of Hippuric acid based on molecularly imprinted copolymer
This study introduces easy detection of Hippuric Acid (HA) through electrochemical polymerization technique. The molecularly imprinted polymer (MIP) was immobilized on a glassy carbon electrode (GCE) through electropolymerization of monomers, including m-dihydroxy benzene (m-DB) and o-aminophenol (o-AP), in presence of HA as the template. Moreover, it was subsequently delineated using electrochemical probe of hexacyanoferrate redox, atomic force microscopy (AFM), fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and electrochemical techniques such as cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). This sensor exhibited limit of detection (0.012 nM) with a good linear range of 0.05–40 nM and 40–500 nM. The developed sensor was properly employed to determine HA in real samples with acceptable results.
Novel Electrochemical Sensor Based on Electropolymerized Dopamine Molecularly Imprinted Polymer for Selective Detection of Pantoprazole
Abstract
Novel Electrochemical Sensor Based on Electropolymerized Dopamine Molecularly Imprinted Polymer for Selective Detection of Pantoprazole
Abstract—In this study, a novel electrochemical sensor through electropolymerization of dopamine (DA) on the surface of the glassy carbon electrode (GCE) was prepared for the determination of Pantoprazole (PAN). Afterwards, it was characterized by scanning electron microscopy (SEM), electrochemical probe of potassium hexacyanoferrate, and electrochemical methods, i.e., differential pulse voltammetry (DPV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The created sensor showed acceptable reproducibility and repeatability, and has a prominent sensitivity and selectivity. It has an acceptable linear range of 0.005 to 1.2 µM, and its limit of detection is 1.3 nM. Finally, the proposed sensor is used to detect PAN in samples of blood serum.
Label-free electrochemical aptasensor for rapid detection of SARS-CoV-2 spike glycoprotein based on the composite of Cu(OH)2 nanorods arrays as a high-performance surface substrate
Abstract
Label-free electrochemical aptasensor for rapid detection of SARS-CoV-2 spike glycoprotein based on the composite of Cu(OH)2 nanorods arrays as a high-performance surface substrate
The development of advanced electrode materials and the combination of aptamer with them have improved dramatically the performance of aptasensors. Herein, a new architecture based on copper hydroxide nanorods (Cu(OH)2 NRs) are directly grown on the surface of screen printed carbon electrode (SPCE) using a two-step in situ, very simple and fast strategy and was used as a high-performance substrate for immobilization of aptamer strings, as well as an electrochemical probe to development a label-free electrochemical aptasensor for SARSCoV-2 spike glycoprotein measurement. The Cu(OH)2 NRs was characterized using X-ray Diffraction (XRD) and electron microscopy (FESEM). In the presence of SARS-CoV-2 spike glycoprotein, a decrease in Cu(OH)2 NRsassociated peak current was observed that can be owing to the target-aptamer complexes formation and thus blocking the electron transfer of Cu(OH)2 NRs on the surface of electrode. This strategy exhibited wide dynamic range in of 0.1 fg mL− 1 to 1.2 µg mL− 1 and with a high sensitivity of 1974.43 μA mM− 1 cm− 2 and low detection limit of 0.03 ± 0.01 fg mL− 1 of SARS-CoV-2 spike glycoprotein deprived of any cross-reactivity in the presence of possible interference species. In addition, the good reproducibility, repeatability, high stability and excellent feasibility in real samples of saliva and viral transport medium (VTM) were found from the provided aptasensor. Also, the aptasensor efficiency was evaluated by real samples of sick and healthy individuals and compared with the standard polymerase chain reaction (PCR) method and acceptable results were observed.
Three-dimensional modeling of streptomycin binding single-stranded DNA for aptamer-based biosensors, a molecular dynamics simulation approach
Abstract
Three-dimensional modeling of streptomycin binding single-stranded DNA for aptamer-based biosensors, a molecular dynamics simulation approach
Streptomycin (STR) an aminoglycoside antibiotic which is used against bacteria in human and animal infection, have serious side effects on different parts of human body. Therefore, there is a crucial need to detect trace amount of it in serum and food products. Aptamers are oligonucleotides or peptides, which bind their targets with high affinity and specificity. These properties make aptamers as suitable candidates for biosensing applications. A 79-mer ss-DNA aptamer was applied for the detection of small amount of STR in various aptasensors. But there is no structural information on the STR-binding aptamer and molecular details underlying the aptamer-STR binding remain unexplored. In this study we provided a 3D-structural model for 79-mer ss-DNA aptamer from the sequence. Using docking program and molecular dynamics (MD) simulation we predicted the binding pocket of ss-DNA aptamer. Our results show STR streptose ring is buried within the groove of DNA model and capped by non Watson-Crick bases. STR interacts with aptamer through forming stable hydrogen bonds. Our computational findings are in fair agreement with experimental results. With the atomic structural details, we gained new insight into the Apt-STR binding interaction that can help to further optimize aptamer efficiency in biosensing applications.
Electronic tongue as innovative instrument for detection of crocin concentration in saffron (Crocus sativus L.)
Abstract
Electronic tongue as innovative instrument for detection of crocin concentration in saffron (Crocus sativus L.)
Electronic tongue is a new approach for simple and fast detection, classification, and quantification of the solved compounds. Crocin is the main source of color of saffron (Crocus sativus L.). An electronic tongue system was used to predict the concentration of saffron crocin in the present study. The measurement system included an electrochemical sensor array based on voltammetry electrodes, a three-electrode cell, a potentiostat, a personal computer. Aqueous analyte were provided by blending pure crocin and different saffron samples from Iran and Spain with distilled water. Output signals of the electronic tongue system were analyzed by principal component analysis and artificial neural networks. Based on principal component analysis, the total variance among pure crocin was 99% and that of saffron samples was 100%. The accuracy of artificial neural network model was 98.80%. The results indicated that the developed electronic tongue system and artificial neural network model can successfully predict crocin concentration in saffron.
Gold nanostructures integrated on hollow carbon N-doped nanocapsules as a novel high-performance aptasensing platform for Helicobacter pylori detection
Abstract
Gold nanostructures integrated on hollow carbon N-doped nanocapsules as a novel high-performance aptasensing platform for Helicobacter pylori detection
Nowadays, there is a lot of interest in the design of advanced nanomaterials in the field of electrochemical aptasensors, which can improve analytical performance. In this work, we have established a synthesis of gold nanostructures supported on hollow carbon N-doped nanocapsules (Au@HNC) for the first time. The TEM, Raman, TGA, FE-SEM, XRD, FT-IR, BET, and EDS mapping were used to morphologically study and characterize the as-prepared Au@HNC nanocapsules. The Au@HNC nanocapsules were used for the ultra-sensitive and fast detection of Helicobacter pylori taking the virtues of good biocompatibility, high electronic conductivity, and large specific surface area. We designed this platform because one of the most well-known problems in the world is Helicobacter pylori infection which causes dangerous stomach diseases. The linearity and detection limit of the Aptamer/Au@HNC aptasensor were found to be 33 CFU mL-1 and 102 to107 CFU mL-1 for Helicobacter pylori, respectively.
Amorphous Ni(OH)2 nano-boxes as a high performance substrate for aptasensor application
Abstract
Amorphous Ni(OH)2 nano-boxes as a high performance substrate for aptasensor application
Recently, the performance of aptasensors has been significantly improved when combined with new nanomaterials. Herein, the amorphous Ni(OH)2 nano-boxes with intact shell structure were synthesized and, then, were used as an efficient substrate for covalent immobilization of the NH2-functionalized aptamer to develop label-free electrochemical aptasensor for ultrasensitive analysis of trypsin. This multidimensional hollow structure places a large amount of surface area in a small space of electrode surface and, thus, increasing the loading of the aptamer strings which significantly increases the sensitivity of measurement. A good linear relationship was found between logarithmic value of trypsin and Rct from 1 fg mL− 1 to 500 ng mL− 1 with a low detection limit of 0.3 fg mL− 1 . Furthermore, the proposed aptasensor showed good reproducibility, high stability and excellent feasibility in biological samples. This study showed that the Ni(OH)2 nano-boxes nanocomposite have various advanced electrochemical properties making them suitable electrode materials for aptasensor application.
A novel ultrasensitive biosensor based on NiCo-MOF nanostructure and confined to flexible carbon nanofibers with high-surface skeleton to rapidly detect Helicobacter pylori
Abstract
A novel ultrasensitive biosensor based on NiCo-MOF nanostructure and confined to flexible carbon nanofibers with high-surface skeleton to rapidly detect Helicobacter pylori
Herein, we aim at designing and synthesizing a specific and sensitive aptasensor for Helicobacter pylori (H. pylori), using a modified electrode with an electrospun nano-sized bimetallic NiCo-metal-organic frameworks nanostructure (NiCo-MOF@C) as platform. As a result, owning to the hydrogen bonds, large amounts of aptamer strands can be bound to the NiCo-MOF@C. The detection limits of 1 CFU. ml−1 and the linearity of 101–107 CFU. ml−1 were obtained. The results of our study show that the proposed impedimetric aptamer-based biosensor has specificity, low detection limit, extended range of linear detection and stability for H. pylori. This new NiCo-MOF@C will become an excellent aptamer-based sensors (aptasensors) platform to detect various analytes.
A novel electrochemical sensor for the determination of histidine based on a molecularly imprinted copolymer
Abstract
A novel electrochemical sensor for the determination of histidine based on a molecularly imprinted copolymer
The present study aimed to report a novel electrochemical sensor through electropolymerization of o-aminophenol (o-AP) and m-dihydroxy benzene (m-DB) as monomers on the surface of the glassy carbon electrode (GCE) for the determination of histidine (His) as a template molecule. The developed sensor exhibited satisfactory sensitivity and high selectivity, and also offered a linear range between 0.005 and 10.0 μM with a detection limit of 0.9 nM. Finally, it is worth mentioning that we also aimed at employing the proposed sensor for the detection of His in blood serum samples.
Selective detection of Asulam with in-situ dopamine electropolymerization based electrochemical MIP sensor
Abstract
Selective detection of Asulam with in-situ dopamine electropolymerization based electrochemical MIP sensor
In this work, a new method is presented based on in-situ electropolymerization of dopamine (DA) monomer and asulam (ASL) as a target molecule to fabricate a molecularly imprinted polymer (MIP) on a glassy carbon electrode (GCE). In this regard, the most basic feature of the prepared sensor is that after template extraction the target molecule, cavities with the same size and stereochemical properties of it, remain on the imprinted polymer matrix. Accordingly, the developed sensing platform showed high selectivity and great sensitivity in ASL detection. The proposed method showed good linear range area from 0.5 to 20 pM with limit of detection of 0.17 pM. The influences of electropolymerization conditions e.g. incubation time, monomer to template concentration, cycle numbers and template extraction time were studied. Finally, it was applied for ASL detection in real samples, and the results were consistent with high-performance liquid chromatography obtained results.
Hierarchical nickel hydroxide nanosheets grown on hollow nitrogen doped carbon nanoboxes as a high-performance surface substrate for alpha-fetoprotein cancer biomarkers electrochemical aptasensing
Abstract
Hierarchical nickel hydroxide nanosheets grown on hollow nitrogen doped carbon nanoboxes as a high-performance surface substrate for alpha-fetoprotein cancer biomarkers electrochemical aptasensing
During recent decades, we have witnessed a great improvement in the performance of aptamer-based sensors, specifically when aptamers are combined with new nanomaterials; as a platform for biosensors. The design of hollow carbon-based materials has also received a lot of attention due to its excellent properties in various applications. Herein, we aim at designing hierarchical porous Ni(OH)2 nanosheets on hollow N-doped carbon nanoboxes Ni(OH)2@N-C n-box). In this sense, we obtained the hollow N-C n-box skeletons from the Fe2O3 nanocubes template. The development of label-free electrochemical aptasensor was carried out using the covalently immobilizing NH2-functionalized aptamer on Ni(OH)2@N-C n-box as an efficient substrate. The Ni(OH)2@N-C n-box was characterized using scanning fourier transform infrared spectroscopy (FTIR), X-ray Diffraction (XRD), Brunauer, Emmett and Teller (BET), transmission electron microscopes (TEM) and electron microscopy (FESEM). The electrochemical evaluations clarified the fact that a linear relationship exists between the alpha-fetoprotein (AFP) contents and the charge transfer resistance (Rct) (from 1 fg mL−1 to 100 ng mL−1) with a low detection limit of 0.3 fg mL−1. Moreover, regarding the aptasensor, the superior detection recoveries were experienced in real biological samples, illustrating its great detection performance and practical feasibility. Considering the aptasensor application, these studies showed that Ni(OH)2@N-C n-box possesses different enhanced electrochemical features, making it appropriate as an electrode material for aptasensor application.
Two-Dimensional Mesoporous Copper Hydroxide Nanosheets Shelled on Hollow Nitrogen-Doped Carbon Nanoboxes as a High Performance Aptasensing Platform
Abstract
Two-Dimensional Mesoporous Copper Hydroxide Nanosheets Shelled on Hollow Nitrogen-Doped Carbon Nanoboxes as a High Performance Aptasensing Platform
The design of metal hydroxide nanosheets on hollow carbonaceous nanostructures has attracted immense attention because of their unparalleled physical/chemical properties with sizeable intrinsic capability to load specific chemicals. Herein, a novel metal hydroxide based on hollow nitrogen-doped carbon nanoboxes shelled with a nanoporous copper hydroxide nanosheet (Cu(OH)2@N−C n-box) was fabricated. The structure of fabricated hollow nanomaterials was fully characterized by various physicochemical characterization techniques such as field emission scanning electron microscopy (FESEM), high-resolu1tion transmission electron microscopy (HRTEM), Brunauer−Emmett−Teller (BET) method, thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), and Fouriertransform infrared (FTIR) and Raman spectroscopies, which confirmed that a complex core−shell structure with ordered two-dimensional Cu(OH)2 nanostructures on N−C n-box was successfully prepared. The Cu(OH)2@ N−C n-box is used to fabricate an advanced electrochemical aptasensor to measure the protein enzyme trypsin. In addition, it acts as an excellent substrate with abundant functional groups and a large surface area for fixing and bonding aptamers on the modified glass-carbon surface. Each step of electrode surface modification was investigated through ferro/ferri cyanide probe signal changes. The designed aptasensor can determine trypsin in a linear concentration between 10 to 80 pg/mL and 10 to 80 ng/mL with a detection limit of 3 pg/mL. The proposed system also has a desirable selectivity in the presence of different interferences. This is the first report on the rational design of hollow carbonaceous materials hybridized Cu(OH)2 for the electrochemical application
An electrochemical immunosensor using SARS-CoV-2 spike protein-nickel hydroxide nanoparticles bio-conjugate modified SPCE for ultrasensitive detection of SARS-CoV-2 antibodies
Abstract
An electrochemical immunosensor using SARS-CoV-2 spike protein-nickel hydroxide nanoparticles bio-conjugate modified SPCE for ultrasensitive detection of SARS-CoV-2 antibodies
As a promising approach for serological tests, the present study aimed at designing a robust electrochemical biosensor for selective and quantitative analysis of SARS-CoV-2-specific viral antibodies. In our proposed strategy, recombinant SARS-CoV-2 spike protein antigen (spike protein) was used as a specific receptor to detect SARS-CoV-2-specific viral antibodies. In this sense, with a layer of nickel hydroxide nanoparticles (Ni(OH)2 NPs), the screen-printed carbon electrode (SPCE) surface was directly electrodeposited to ensure better loading of spike protein on the surface of SPCE. The differential pulse voltammetry (DPV) showed signals which were inversely proportional to the concentrations of the antibody (from 1 fg mL− 1 L to 1 µg mL− 1 ) via a specific and stable binding reaction. The assay was performed in 20 min with a low detection limit of 0.3 fg mL− 1 . This biodevice had high sensitivity and specificity as compared to non-specific antibodies. Moreover, it can be regarded as a highly sensitive immunological diagnostic method for SARS-CoV-2 antibody in which no labeling is required. The fabricated hand-held biodevice showed an average satisfactory recovery rate of ~99-103% for the determination of antibodies in real blood serum samples with the possibility of being widely used in individual serological qualitative monitoring. Also, the biodevice was tested using real patients and healthy people samples, where the results are already confirmed using the enzyme-linked immunosorbent assay (ELISA) procedure, and showed satisfactory results.
Electrochemical Detection of Celestine Blue Based on Screen Printed Carbon Electrode Modified with Molecular Imprinted Polymer and NiO Nanoparticles
Abstract
Electrochemical Detection of Celestine Blue Based on Screen Printed Carbon Electrode Modified with Molecular Imprinted Polymer and NiO Nanoparticles
A simple and rapid electrochemical method was developed for the detection of trace amount of Celestine blue (CB) at the surface of modified screen-printed carbon electrode (SPCE) with nickel oxide (NiO) nanoparticles and molecular imprinted polymer (MIP). Various types of electrochemical methods; containing, differential pulse voltammetry (DPV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in order to probe the characteristics of the sensor toward CB was employed. The selectivity, real sample analysis (efficiency), the linear concentration range, and the detection limit of CB at the MIP/NiO-NPs/SPCE were evaluated by DPV method. FT-IR spectroscopy was applied in order to characterize the synthesized CB-MIP and non-molecular imprinted polymers (NIP). Scanning electron microscopy (SEM) and BET (Brunauer-Emmett-Teller) techniques were used for surface morphology and porosity properties of CB-MIP and NIP. A linear range was presented by the sensor for CB concentration between 2-150 µM with detection limit (S/N=3) of 0.35 µM. The sensor is able to selectively detect the CB molecules over the potential interferences. The sensor was used to determine CB in the real sample with acceptable results.
Metal–organic framework-derived CoNi-P nanoparticles confined into flexible carbon nanofibers skeleton as high-performance oxygen reduction reaction catalysts
Abstract
Metal–organic framework-derived CoNi-P nanoparticles confined into flexible carbon nanofibers skeleton as high-performance oxygen reduction reaction catalysts
The rational design of high performance oxygen reduction reaction (ORR) catalysts based on metal chalcogenides derived carbon materials with stable porous structure and rapid electron/mass transport properties is highly desirable yet a great challenge to date. Herein, we synthesize and design metal–organic framework-derived CoNiP nanoparticles confined into a flexible carbon nanofiber skeleton (C@CoNi-P@C) as ORR catalysts with excellent activity. Using electrospinning of nano size bimetallic NiCo-MOF particles, followed by a precisely controlled annealing process at PH3 atmosphere, composite C@CoNi-P@C catalysts with uniform fiber morphology can be obtained. By comparing the catalytic performance with pure CNF, it is found that the C@CoNi-P@C mixture can be better for the ORR catalyst. With these favorable features, C@CoNi-P@C exhibits an overall distinguished ORR performance in alkaline media, which has a high onset potential of 0.83 V (vs. RHE), half-wave potential of 0.73 V (vs. RHE) and electron transfer number (4). This work introduces a new concept for design of new electrocatalysts using the electrospinning technique for energy storage and conversion application.
Rationally designed of hollow nitrogen doped carbon nanotubes double shelled with hierarchical nickel hydroxide nanosheet as a high performance surface substrate for cortisol aptasensing
Abstract
Rationally designed of hollow nitrogen doped carbon nanotubes double shelled with hierarchical nickel hydroxide nanosheet as a high performance surface substrate for cortisol aptasensing
The development of advanced electrode materials based on hollow metal hydroxide nanosheets/carbonaceous nanostructures that have unique chemical/physical properties and sizeable inherent cavity to load specific chemical, has attracted immense attention. Herein, novel metal hydroxide nanosheets/carbonaceous nanostructures based on hollow mesoporous Ni(OH)2 nanosheet double shelled on hollow nitrogen doped carbon nanotubes (Ni(OH)2@N–C n-Tube) were designed. The N–C n-Tube skeleton was derived from its corresponded Fe2O3 nanorod with a simple self-polymerizing method, followed by an annealing and etching method. This advanced core-double shell array with ordered hierarchical Ni(OH)2 nano-architectures was successfully used as a high performance surface substrate for cortisol (COR) aptasensing. The Ni(OH)2@N–C n-Tube shows unique characteristics including high surface area with rich functional group for bonding and fixing aptamer when used as a surface substrate. This proposed aptasensor can detect COR in a linear concentration between 1 pM to 80 pM and 0.1 nM to 25 nM with a detection limit of 0.3 pM and good selectivity in the presence of various interferences
Rapid and sensitive determination of Pseudomonas aeruginosa by using a glassy carbon electrode modified with gold nanoparticles and aptamer-imprinted polydopamine
Abstract
Rapid and sensitive determination of Pseudomonas aeruginosa by using a glassy carbon electrode modified with gold nanoparticles and aptamer-imprinted polydopamine
seudomonas aeruginosa causes a long-term chronic disease that low concentrations of Pseudomonas aeruginosa can cause infection; therefore, rapid detection of this Pseudomonas aeruginosa is very important. This study presents a method with a combination of molecular imprinting and aptasensing in order to measure Pseudomonas aeruginosa (P. aeruginosa). The double exact molecular recognition property of the molecular imprinting polymers and aptamers led to superb sensing properties. In this study, gold nanoparticles were used as specific intermediate and interface in order to increase the aptamer sequence loading rate. The capability of this method was investigated by several electrochemical techniques. The sensor renders a wide linear dynamic concentration range of 101 to107 CFU·ml−1 with low detection limit of 1 CFU·ml−1. In addition, satisfactory results were found in determining P. aeruginosa using blood samples. This sensor has many advantages, such as low cost, high stability, low response time, and high sensitivity for P. aeruginosa measurement.
Aptamer-based electrochemical detection of Tyrosinamide using metal-organic frameworks/silver nanoparticles modified glassy carbon electrode
Abstract
Aptamer-based electrochemical detection of Tyrosinamide using metal-organic frameworks/silver nanoparticles modified glassy carbon electrode
In this report, a new aptamer-based assay was presented reporting the electrochemical aptasensing for sensing tyrosinamide (Tyr-NH2). This strategy was relied on unbeatable conformational flexibility and specific recognition of aptamers. The tyrosinamide aptamer (Tyr-NH2-aptamer) was immobilized onto the metal-organic frameworks/silver nanoparticles modified glassy carbon electrode and hexacyanoferrate was selected as a probe to monitor interface variations during modification of the electrode and the aptamer conformational change generated by the Tyr-NH2 binding. Results showed that measurements by using electrochemical impedance spectroscopy had linear with the Tyr-NH2 concentrations in range of 0.01-0.25 nM and 0.25-1.15 nM. Detection limit of this system was found to be 2.3 pM. This method was also used to the Tyr-NH2 detection in serum samples successfully. Remarkable simplicity, ease of use and low-cost, make methodology as sensitive analytical system for sensing of the Tyr-NH2 that can be miniaturized. This strategy offers some promising advantages in reliable detection of the Tyr-NH2, which may be helpful in the routine analysis.
Flexible NiP2@hollow N-doped nanocapsules/carbon nanofiber as a freestanding electrode for glucose sensing
Abstract
Flexible NiP2@hollow N-doped nanocapsules/carbon nanofiber as a freestanding electrode for glucose sensing
The development of flexible and binder free electrocatalytic materials based on low cost metal dichalcogenide and low weight carbon nanofibers (CNF) has been materialized as an effective strategy for the fabrication of advanced super light portable, wearable, and stretchable sensor devices. In this work, the NiP2/hollow N-doped nanocapsules decorated nitrogen-doped carbon nanofiber (NiP2/CNCNF), have been designed for the first time. The NiP2/CNCNF was used directly as a flexible and freestanding electrode toward electrocatalytic and nonoenzymatic glucose sensing. The NiP2/CNCNF displayed high conductivity, flexibility with low weight, excellent electrochemical activity, steadiness and enhanced electron transfer rate.
Electrochemical immunosensor with Cu2O nanocube coating for detection of SARS-CoV-2 spike protein
Abstract
Electrochemical immunosensor with Cu2O nanocube coating for detection of SARS-CoV-2 spike protein
Severe acute respiratory syndrome SARS-CoV-2 has caused a global pandemic starting in 2020. Accordingly, testing is crucial for mitigating the economic and public health effects. In order to facilitate point-of-care diagnosis, this study aims at presenting a label-free electrochemical biosensor as a powerful nanobiodevice for SARS-CoV-2 spike protein detection. Utilizing the IgG anti-SARS-CoV-2 spike antibody onto the electrode surface as a specific platform in an ordered orientation through staphylococcal protein A (ProtA) is highly significant in fabricating the designed nanobiodevice. In this sense, the screen-printed carbon electrode modified with Cu2O nanocubes (Cu2O NCs), which provide a large surface area in a very small space, was applied in order to increase the ProtA loading on the electrode surface. Accordingly, the sensitivity and stability of the sensing platform significantly increased. The electrochemical evaluations proved that there is a very good linear relationship between the charge transfer resistance (Rct) and spike protein contents via a specific binding reaction in the range 0.25 fg mL−1 to 1 μg mL−1 . Moreover, the assay when tested with influenza viruses 1 and 2 was performed in 20 min with a low detection limit of 0.04 fg mL−1 for spike protein without any cross-reactivity. The designed nanobiodevice exhibited an average satisfactory recovery rate of ~ 97–103% in different artificial sample matrices, i.e., saliva, artificial nasal, and universal transport medium (UTM), illustrating its high detection performance and practicability. The nanobiodevice was also tested using real patients and healthy samples, where the results had been already obtained using the standard polymerase chain reaction (PCR) procedure, and showed satisfactory results.
Hollow carbon nanocapsules-based nitrogen-doped carbon nanofibers with rosary-like structure as a high surface substrate for impedimetric detection of Pseudomonas aeruginosa
Abstract
Hollow carbon nanocapsules-based nitrogen-doped carbon nanofibers with rosary-like structure as a high surface substrate for impedimetric detection of Pseudomonas aeruginosa
The design of hollow mesoporous carbon-based materials has attracted tremendous attention, due to their sizeable intrinsic cavity to load specific chemical and unique physical/chemical properties in various applications. Herein, we have established an effective strategy for the preparation of novel hollow carbon nanocapsulesbased nitrogen-doped carbon nanofibers (CNCNF) with rosary-like structure. By embedding ultrafine hollow carbon nanocapsules into electrospun polyacrylonitrile (PAN) skeleton, the as-designed composite CNFs were carbonized into hierarchical porous CNFs, consisted of interconnected nitrogen-doped hollow carbon nanocapsules. Due to its individual structural properties and unique chemical composition, the performance of CNCNF was evaluated in aptasensor application via the detection of Pseudomonas aeruginosa (PA). Under optimized conditions, the aptasensor based on CNCNF has a detection limit of 1 CFU⋅mL− 1 and a linear range from 101 CFU ⋅mL− 1 to 107 CFU ⋅mL− 1 (n = 3). Moreover, the designed aptasensor possesses high sensivity, high selectivity, low detection limit, and high reproducibility. These studies showed that the CNCNF material offers a wide variety of enhanced electrochemical features as an electrode material for aptasensor application.
Fabrication of an electrochemical biodevice for ractopamine detection under a strategy of a double recognition of the aptamer/molecular imprinting polymer
Abstract
Fabrication of an electrochemical biodevice for ractopamine detection under a strategy of a double recognition of the aptamer/molecular imprinting polymer
The importance of RAC tracking in human biofluids has boosted many demands for designing an ultrasensitive tool to determine the trace value of the RAC from clinical, judicial, and forensic centers. In this study, an electrochemical biodevice has developed for the highly selective detection of this illegal feed additive under a double recognition strategy of the aptamer (Apt) and molecular imprinting polymer (MIP) on a glassy carbon electrode (GCE). The sensing relies on this fact that both the MIP and Apt act synergistically to trap the RAC molecules. The sensing surface fabrication steps have been monitored by some electrochemical techniques such as electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV(. The charge transfer resistance (Rct) value of the redox probe as a representative of the biodevice response has increased linearly with the RAC concentration increasing in a dynamic range of 1 fM to 1.90 mM. The detection limit (LOD) value has been estimated to be 330 aM, lower than all of the reported methods in the RAC sensing. Furthermore, the practical feasibility of biodevice has been evaluated in some human blood serum and urine samples. This strategy offers some useful advantages in reliable detection of the RAC, which may help in the routine analysis, as mandated by regulatory agencies.
Applications of electronic tongue system for quantifcation of safranal concentration in safron (Crocus sativus L.)
Abstract
Applications of electronic tongue system for quantifcation of safranal concentration in safron (Crocus sativus L.)
In the present research the electronic tongue system was proposed consisted of an array of 4 voltammetric sensors to discriminate saffron samples based on the safranal concentration. Different samples were provided by blending saffron samples with distilled water and pure safranal with ethanol. The provided signals by the electronic tongue system were analyzed using the PCA and ANN methods. The total variance among safranal concentrations by PCA method were 90% and 100% in pure safranal and saffron samples, respectively. Also, it was revealed that the electronic tongue could provide good prediction for safranal concentration in saffron as 98.81% accuracy by means of optimized ANN model. Results showed that there are some relationships between HPLC and electronic tongue signals to determine safranal concentration levels in different saffron samples.
Three-dimensional NiCo2O4 nanowires encapsulated in nitrogen-doped carbon networks as a high-performance aptamer stabilizer for impedimetric ultrasensitive detection of hepatitis C virus core antigen
Abstract
Three-dimensional NiCo2O4 nanowires encapsulated in nitrogen-doped carbon networks as a high-performance aptamer stabilizer for impedimetric ultrasensitive detection of hepatitis C virus core antigen
Recently, the performance of aptamer-based sensors has been greatly improved by the combination of aptamers with novel nanomaterials. Herein, the hierarchical porous 3D-NiCo2O4 nanowires, shelled with a thin layer of Ndoped carbon (l) with sea-urchin-like morphology, were successfully prepared by a facile protocol. The 3D NC@NiCo2O4 NWs combine the electrochemical advantages of Ni and Co species by exhibiting higher specific capacitance and active sites and also much higher conductivity. More significantly, the carbon layer improves the stability, conductivity and porosity of the nanowires. Benefiting from such a hierarchical structure, 3D NC@NiCo2O4 NWs fit a large amount of surface area in a very small space. Therefore, the 3D N-C@NiCo2O4 NWs was applied in order to increase the hepatitis C virus core antigen (HCV) aptamer load on the electrode that significantly increased the sensitivity of the sensor. The electrochemical evaluations were proved that there exists a very good linear relationship between the charge transfer resistance (Rct) and HCV contents in the range of 0.5 fg mL− 1 to 0.12 pg mL− 1 with a low detection limit of 0.16 fg mL− 1 . Besides, it was in real biological samples that the aptasensor experienced superior detection recoveries which illustrated its high detection performance and feasibility for practicability.
Sensitive amperometric detection of hydrazine using a rutin/ graphene-chitosan nanocomposite modified glassy carbon electrode
Abstract
Sensitive amperometric detection of hydrazine using a rutin/ graphene-chitosan nanocomposite modified glassy carbon electrode
The present study describes a new approach for the investigation of electrocatalytic oxidation of hydrazine by using a glassy carbon electrode (GCE) modified by graphene chitosan nanocomposite (Gr-Cs) and Rutin (Ru). The heterogeneous electron transfer rate constant (ks) and the surface coverage of immobilized Ru on the Gr‒Cs/GCE were obtained as 63 s−1 and 4.48×10−11 mole cm−2, respectively. The designed sensor showed excellent electrocatalytic activity toward oxidation of hydrazine. The catalytic rate constant (kcat) of the modified electrode toward N2H4 is 6.3 ×103 M-1s-1. Linear relationship between amperometric current response and hydrazine concentration was observed in the range of 0.3-1500 µM and the limit of detection was 90 nM (S/N=3). In addition, the modified electrode has an excellent anti-interference property in the presence of other potentially interfering species as well as a good operational stability. To evaluate the applicability of the proposed sensor, it was employed to determine hydrazine in a drinking water sample
Electrochemical immunosensor for determination of Staphylococcus aureus bacteria by IgY immobilized on glassy carbon electrode with electrodeposited gold nanoparticles
Abstract
Electrochemical immunosensor for determination of Staphylococcus aureus bacteria by IgY immobilized on glassy carbon electrode with electrodeposited gold nanoparticles
A new ultrasensitive immunosensor is proposed based on the covalently attached anti-protein A antibody (IgY) on deposited gold nanoparticle (AuNP)-modified glassy carbon electrode (GCE) for the electrochemical measurement of Staphylococcus aureus (S. aureus). Chicken IgY as a capture antibody provides highly selective and specific binding to the target bacteria and selectively captures the S. aureus in its three-dimensional space. Due to that it can eliminate the interference from protein G-producing Streptococcus. In addition, the electron-transfer characteristic of [Fe(CN)6] 4−/3− is hindered by this combination; as it is reflected on the electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) curves. The proposed immunosensor displays a wide linear dynamic range from 10 to 107 CFU mL−1 with a detection limit of 3.3 CFU mL−1 with RSD 3.0%. It is capable to accurately determine S. aureus in milk and human blood serum as a complex matrix sample with satisfactory recovery of ∼ 97–103%. The immunosensor also displays high selectivity over other bacteria and acceptable stability. Presumably, our study can be regarded as the first one to report chicken IgY in order to detect S. aureus based on an electrochemical method.
Cu-In-S/ZnS quantum dots/silver nanoparticles nanocomposites-modified electrode as an electrochemical label-free aptasensor for the detection of β-casomorphin 7 in early distinguish of autism
Abstract
Cu-In-S/ZnS quantum dots/silver nanoparticles nanocomposites-modified electrode as an electrochemical label-free aptasensor for the detection of β-casomorphin 7 in early distinguish of autism
In this study, the efficiency of a nanocomposite contains the quantum dots and silver nanoparticle (AgNP/QDs) has been investigated to modify a glassy carbon electrode (GCE) in the aptasensor construction. Accordingly, the modified GCE provides a sub-layer to load more aptamers (Apts) through a linker agent of the AgNP to identify the β-casomorphin 7 (BCM-7) as an autism biomarker. The Apt/target interaction on the sensing interface surface leads to an electron transfer hindrance of the Rutin (RU) as a green redox probe. Consequently, a corresponding decrease in the current signal of the RU is achieved. The electrochemical studies show that the obtained signal responses linearly correlate with various BCM-7 concentrations in two ranges of 1 pM-20 nM and 20 nM-1.3 µM with a calculated limit of detection (LOD) 332 fM. The label-free aptasensor presents a high selectivity towards the BCM-7 in the presence of several similar amino acids. The analysis of the human urine and blood samples demonstrates the sufficient capability of the aptasensor in the BCM-7 detection in the real samples.
Facile synthesis of a covalent organic framework (COF) based on the reaction of melamine and trimesic acid incorporated electrospun nanofiber and its application as an electrochemical tyrosinamide aptasensor
Abstract
Facile synthesis of a covalent organic framework (COF) based on the reaction of melamine and trimesic acid incorporated electrospun nanofiber and its application as an electrochemical tyrosinamide aptasensor
In this research, for the first time, a high-performance electrochemical aptasensor assay based on electrospun covalent organic framework (COF) nitrogen-doped carbon nanofiber (COFCNF) was designed and dedicated to tyrosinamide sensing. The COF is prepared via a condensation reaction between trimesic acid and melamine. The COFCNF has been used to modify the electrode surface in an electrochemical sensor based on the aptamer because the COFCNF increases electrochemical activity. The as-prepared nanofibers were characterized by Brunauer Emmett Teller analysis, Field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. Electrochemical impedance spectroscopy and cyclic voltammetry were used for the fabrication and assessment of the proposed aptasensor in Fe(CN)64−/3− as a redox probe. The proposed aptasensor for tyrosinamide has a detection limit of 0.53 pM and linearity from 0.0016 to 0.08 nM and 0.08–9 nM.
Hierarchical hollow sea-urchin-like Ni–Co diselenide encapsulated in N-doped carbon networks as an advanced core-shell bifunctional electrocatalyst for fabrication of nonenzymatic glucose and hydrogen peroxide sensors
Abstract
Hierarchical hollow sea-urchin-like Ni–Co diselenide encapsulated in N-doped carbon networks as an advanced core-shell bifunctional electrocatalyst for fabrication of nonenzymatic glucose and hydrogen peroxide sensors
The design of bimetallic selenide configurations has been regarded as a feasible strategy to modulate the electronic structure of the electrocatalysts for sensors application. In this sense, unique hierarchical porous threedimensional Ni–Co diselenide nanowires (3D Co0.6Ni0.4Se2 NWs) coated with N-doped carbon thin layer (3D N-C@Co0.6Ni0.4Se2 NWs) with hollow sea-urchin-like overall morphology were fabricated and used as an effectual bifunctional electrocatalyst for glucose oxidation and hydrogen peroxide reduction. Regarding the advantages of this porous and 3D structure, the N-C@Co0.6Ni0.4Se2 NWs offer abundant electrochemical-active sites, high availability to the electrolyte/analyte, and high conductivity due to the synergistic effect of bimetals, coated N-doped carbon and selenide. As an amperometric glucose sensor, it shows a high sensitivity of 1439 and 239 μA mM− 1 cm− 2 and wide linear range from 0.5 μM to 2.2 mM and 2.2 mM–12.2 mM with a low detection limit of 0.16 μM. Moreover, amperometric H2O2 sensing will be recognized with a sensitivity of 89 and 31.8 μA mM− 1 cm− 2 , a linear range from 0.5 μM to 6 mM and 6 mM–15 mM, and a detection limit of 0.16 μM (S/N = 3). Moreover, the developed sensor shows a great potential in determining glucose and H2O2 in biological real samples.
Design of an electrochemical aptasensor based on porous nickel‑cobalt phosphide nanodiscs for the impedimetric determination of ractopamine
Abstract
Design of an electrochemical aptasensor based on porous nickel‑cobalt phosphide nanodiscs for the impedimetric determination of ractopamine
A trend in the development of aptasensors is introducing high-performance nanomaterials as a platform of biosensors with suitable aptamer binding capacity and good electrochemical activity. Here, for the first time, we report the application of nickel‑cobalt phosphide nanodiscs (NiCo-P NDs) in the design of an aptasensor for the impedimetric determination of ractopamine (RAC). The highly porous NiCo-P NDs were synthesized by a simple two-step method. Due to the high porosity and large specific surface area of NiCo-P NDs, it increases the loading of the aptamers on the modified electrode and improves the performance of the proposed aptasensor. Under optimal conditions, the designed aptasensor could determine RAC in a wide linear concentration range from 0.50 f. to 1.25 μM and has an ultralow limit of detection (LOD) of 166 aM (S/N = 3). The fabricated electrochemical aptassensor is reproducible, selective, cost-effective, which was successfully used to RAC detection in blood serum samples. We hope that our study will develop the application of the multi-metal phosphide nanodiscs in biosensing devices.
Rational design of hollow core-double shells hybrid nanoboxes and nanopipes composed of hierarchical Cu-Ni-Co selenides anchored on nitrogen‐doped carbon skeletons as efficient and stable bifunctional electrocatalysts for overall water splitting
Abstract
Rational design of hollow core-double shells hybrid nanoboxes and nanopipes composed of hierarchical Cu-Ni-Co selenides anchored on nitrogen‐doped carbon skeletons as efficient and stable bifunctional electrocatalysts for overall water splitting
It is of prime importance to develop efficient nonprecious noble-metal-free water splitting bifunctional electrocatalysts for both H2 and O2 evolution reactions (HER and OER), which remains a grand challenge. However, the design of hollow nanostructured based on di- and tri-metal selenides, particularly non-spherical hollow nanostructures, is scarcely reported. Herein, for the first time, novel tri-metal selenides based on hollow Cu0.4Ni0.3Co0.3Se2 mesoporous nanosheet double shell were successfully designed on hollow N-doped carbon nanoboxes (Cu0.4Ni0.3Co0.3Se2@N-C n-box) and nanopipes (Cu0.4Ni0.3Co0.3Se2@N-C n-pipe). The hollow N-C n-box and N-C n- pipe skeletons were obtained from the related Fe2O3 nanocubes and nanorods templates that have prepared with completely different morphologies via only a minor change in synthesis step. Remarkably, benefiting from the special electronic structure engineering and unique hollow hierarchical design with high surface areas, open channels for effective gas releasing, fast electron/mass transport, the resulting advanced electrocatalysts provide outstanding OER activity as well as desirable HER performance in the alkaline medium. Moreover, an overall water splitting device is assembled using two symmetrical Cu0.4Ni0.3Co0.3Se2@N-C n-box electrodes as anode and cathode, which can deliver a current density of 10 mA cm−2 at a cell voltage as low as 1.53 V. More significantly, in addition to extraordinary operational stability of the electrolyzer, it can achieve high current density of 100 mA cm−2 with only cell voltage of 1.79 V, respectively, which are very useful for practical application. This work offers a rational strategy for the structure engineering of advanced hollow hybrid nanostructures as a nonprecious noble-metal-free water splitting
Determination of BCM-7 based on an ultrasensitive aptasensor fabricated of gold nanoparticles and ZnS quantum dots
Abstract
Determination of BCM-7 based on an ultrasensitive aptasensor fabricated of gold nanoparticles and ZnS quantum dots
In thisstudy, anultrasensitive electrochemical aptasensor for the determination oftheβ-casomorphin 7(BCM-7) as a promising biomarker of autism disorder is introduced. According to the proposed strategy, a glassy carbon electrode (GCE) was modified by thiourea capped-ZnS QDs (ZnS-QDs) and gold nanoparticles (AuNPs) to further immobilization the amino-aptamer (NH2-Apt) on its surface. The NH2-Apt as a receptor of the BCM-7 was attached to the embedded surface via a formation of the Au–N bonds between the AuNPs and amino groups of the Apt. The evaluation of aptasensor by various electrochemical techniques exhibited successful sensing of the BCM-7 under twobroadlinear concentration ranges from1fM to0.6μMwitha limit ofdetection (LOD) down to 350aM. Also, the performance of the aptasensor in BCM-7 detection in real human urine samples was satisfactorily investigated. These findings may facilitate distinguish of this challenging disorder and help human health.
Pd/[C2NH2mim][Br] Thin Film Versus Pd/[C8mim][Cl] or Pd/[C8mim] [BF4]: Catalytic Applications in Electrooxidation of Methanol, p‑Nitrophenol Reduction and C–C Coupling Reaction
Abstract
Pd/[C2NH2mim][Br] Thin Film Versus Pd/[C8mim][Cl] or Pd/[C8mim] [BF4]: Catalytic Applications in Electrooxidation of Methanol, p‑Nitrophenol Reduction and C–C Coupling Reaction
In this study, diferent ionic liquids including 1-aminoethyl-3-methyl-imidazolium bromide [C2NH2mim][Br] (1), 1-methyl3-octylimidazolium chloride [C8mim][Cl] (2) and 1-methyl-3-octylimidazolium tetrafuoroborate [C8mim][BF4] (3) were applied to stabilize Pd nanoparticles (NPs) at toluene/water interface as thin flms. Field emission-scanning electron microscopy (FE-SEM) images showed puckered chains of ionic liquid (1) around the Pd NPs as fower nanostructures. Transmission electron microscopy (TEM) image of Pd/1 showed clearly core–shell nanostructures. Furthermore, applications of Pd/1, Pd/2 and Pd/3 were investigated in the Suzuki–Miyaura C–C coupling reaction in the presence and absence of ultrasonic waves, hydrogenation catalysis of p-nitrophenol reduction and methanol oxidation reaction. Interestingly, Jf (forwarding current density due to methanol oxidation) was observed only for Pd/1. We believe that interactions of –NH2 and imidazolium groups of ionic liquid 1 with Pd particles are very important in producing of puckered shells around the Pd NPs. Injection of electron density from –NH2 group and Br− of ionic liquid 1 to Pd content tends to Pd be softer than other ionic liquids (2 or 3). This efect weakens the strength of Pd–O and facilitates the intermolecular reductive elimination between Pd–O and Pd–C≡O in rate-determining step of methanol oxidation to produce CO2 product. However, electron releasing group accelerates the increasement in negative charge density of metal accelerates intramolecular or intermolecular reduction elimination.
Architecting of a biodevice based on a screen-printed carbon electrode modified with the NiONP nanolayer and aptamer in BCM-7 detection
Abstract
Architecting of a biodevice based on a screen-printed carbon electrode modified with the NiONP nanolayer and aptamer in BCM-7 detection
In this study, an ultrasensitive and robust biodevice implemented on a screen-printed carbon electrode (SPCE) surface is introduced. The β-casomorphin-7 (BCM-7) peptide as an early warning sign of autism disorder is distinguished in this system. The SPCE surface was directly electrodeposited with a nanolayer of the nickel oxide nanoparticles (NiONP). In next step, an Apt sequence as a capture of the BCM-7 was strongly attached on this surface. The embedded sensing interface offered some admirable characterizes to detect the BCM-7. The obtained DPV signals were reversely proportional to the concentrations of the BCM-7 through a stable binding reaction in two working linear ranges from 0.5 × 10−9-1.5 μmol l-. Also, an unrivaled limit of detection (LOD) value of 166.6 aM was achieved that is so superior by other reported methods in the BCM-7 sensing. This hand-held biodevice was satisfactorily tested for the BCM-7 detection in human urine and blood sample with an average recovery rate of ∼101.87 %. More importantly, this strategy is free from labeling steps, complex sample processing and interference from common biomolecules in blood or urine. Due to the inherent advantages of the SPCE and the NiONP, utilizing this facile sensing interface may be an ideal choice in constructing of the ultrasensitive biodevice with low cost for distinguishing of the autism disorder.
Designing of an ultrasensitive BCM-7 aptasensor based on an SPCE modified with AuNR for promising distinguishing of autism disorder
Abstract
Designing of an ultrasensitive BCM-7 aptasensor based on an SPCE modified with AuNR for promising distinguishing of autism disorder
Abstractly, in this study, an aptasensor is introduced based on a platform consisting of the gold nanorod (AuNR) on a screen printed carbon electrode (SPCE) surface. The aptasensor is applied for detection of the β-casomorphin (BCM-7) as a promising biomarker of autism disorder. The NH2-Apt sequence is directly immobilized onto the AuNR/SPCE surface by formation of a chemisorption bond between the amine-Au groups. By incubation of the BCM-7 onto the aptasensor surface, the aptasensor directed against BCM-7 and cleverly formed a target/Apt complex to produce a measurable electrical current change. The aptasensor shows linearity over the range of 1 fmol L−1 to 25 nmol L−1 with a limit of detection (LOD) of 334 amol L−1. Furthermore, the function of the aptasensor in real samples such as human urine and plasma samples is evaluated. The achieved satisfactory results are mainly due to three main reasons including (1) the large specific surface area of the AuNR which forms a 3D network on the SPCE surface to capture more Apt sequences at the sensing interface, (2) utilizing Apt as the BCM-7 receptor with inherent unique properties to produce a synergetic effect with the AuNR, and finally, (3) effective using screen printing technology with the fantastic capability to less cost of the aptasensor preparation. There is hope that miniaturization of the proposed aptasensor may aid future efforts to detect autism symptoms as early as infancy under clinical conditions in real-world.
Development of an Electrochemical Sensor for a Sensitive Determination of Metanil Yellow
Abstract
Development of an Electrochemical Sensor for a Sensitive Determination of Metanil Yellow
In this work, we introduced a sensitive electrochemical sensor in order to accurately detect metanil yellow (MY). Multi-walled carbon nanotube-chitosan (MWCNTs-Chit) nanocomposite was applied to fabricate the sensor on the glassy carbon electrode. The scanning electron microscopy (SEM) was used to investigate the physical morphology of the modified electrode surface. The rate of the electron transfers between MY and electrode can be quickened by the attendance of MWCNTs-Chit nanocomposite due the high surface area, good conductivity as well as excellent catalytic property. Sensitive quantitative detection of the MY was carried out by the monitoring increase of differential pulse voltammetric (DPV) responses of the sensor. The prepared MWCNTs-Chit/GC electrode illustrated a linear response to MY concentration in the range of 1.0 µM to 300.0 µM with a sensitivity and a limit of detection (S/N=3) of 20.0 nAµM-1 and 0.3 µM, respectively. Accordingly, in order to determine MY in real samples with satisfactory results, we applied the proposed sensor.
Electroanalytical sensing of Asulam based on nanocomposite modified glassy carbon electrode
Abstract
Electroanalytical sensing of Asulam based on nanocomposite modified glassy carbon electrode
In this study a facile approach to employ Copper nanoparticle (CuNPs) and multi-walled carbon nanotubes (MWCNT) as the nanomaterial for selective detection of asulam have been investigated. This work reports the electrocatalytic oxidation of asulam on glassy carbon electrodes (GCE) modified with multi-walled carbon nanotubes (MWCNT), ionic liquids (IL), chitosan (Chit) and copper nanoparticles (CuNPs).Using the proposed nanocomposite provides a specific platform with increased surface. The surface morphology of this modified electrode was characterized by field-emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectrometer (EDX) techniques. The electrochemical behaviors of the fabricated sensor were investigated by cyclic voltammetry (CV) and chronoamperometry modes. Under optimal conditions, the amperometric study exhibits two linear ranges of 1–11 and 11–200 μmol L-1 with a detection limit (LOD) of 0.33 nmol L-1 (at an S/N of 3) and sensitivity of 1.9 nA μmol L-1 for Asulam determination. This novel sensor was used to analyze the real sample. The sensor provides a convenient, low-cost and simple method for Asulam detection and proposes new horizons for quantitative detection of Asulam.
AgNPs/QDs@GQDs nanocomposites developed as an ultrasensitive impedimetric aptasensor for ractopamine detection
Abstract
AgNPs/QDs@GQDs nanocomposites developed as an ultrasensitive impedimetric aptasensor for ractopamine detection
Developing easy-to-use and miniaturized sensors for in-field monitoring of targets which is related to human health is necessary. Ractopamine (RAC) is a feed additive with serious side effects that is forbidden in many countries. This study reports the fabrication of an impedimetric aptasensor for ultrasensitive and selective detection of the RAC in human biological fluids. Accordingly, an efficient nanocomposites was synthesized by a beneficial combination of graphene quantum dots (GQDs), quantum dots (QDs) and silver nanoparticles (AgNPs) for modifying a glassy carbon electrode (GCE). This nanocomposite is promising to present a synergistic effect in the increase of the active surface area of the modified electrode to more load the biocapture of the target. Next, the RAC-binding aptamer (Apt) was attached to the AgNPs/QDs@GQDs/GCE surface and a sensitive layer for the RAC detection was embedded. A RAC-Apt complex was formed upon adding the RAC and the changes of the electrochemical behavior were studied by some electrochemical techniques such as electrochemical impedance spectroscopy (EIS). Under optimal conditions, the charge transfer resistance (Rct) value was increased linearly with increasing of the RAC concentrations in the range of 1 fM to 901.4 nM. Limit of detection (LOD) was calculated to be 330 aM which is superior by other reported electrochemical methods in the RAC sensing. The applicability of the aptasensor was tested in human urine and blood serum as the real samples and satisfactory results of specificity were achieved. It seems that the proposed strategy not only provides a new ultrasensitive strategy for RAC detection but also expands the application of the sensing interface to develop other aptasensors by changing the Apt sequence.
Impedimetric aptasensor for Pseudomonas aeruginosa by using a glassy carbon electrode modified with silver nanoparticles
Abstract
Impedimetric aptasensor for Pseudomonas aeruginosa by using a glassy carbon electrode modified with silver nanoparticles
An aptasensor is described for the ultrasensitive detection of Pseudomonas aeruginosa (P. aeruginosa). A glassy carbon electrode (GCE) was first modified by electrodeposition of silver nanoparticles (AgNPs). Immobilization of NH2-aptamer was covalently attached to the AgNP/GCE surface. The morphology, distribution and size of the sensor were characterized by field emission scanning electron microscopy. Cyclic voltammetry and electrical impedance spectroscopy were used to study conductivity of the aptasensor and the electrochemical properties. Detection of P. aeruginosa was carried out by evaluation of the charge transfer resistance after and before the adding of P.aeruginosa and by using the hexacyanoferrate redox system as an electrochemical probe. The impedance increases on going from 102 to 107 CFU·mL−1 concentrations of P. aeruginosa, and the detection limit is 33 CFU·mL−1 (for S/N = 3). The assay was successfully applied for the determination of P. aeruginosa in spiker serum samples.
The development of an electrochemical nanoaptasensor to sensing chloramphenicol using a nanocomposite consisting of graphene oxide functionalized with (3‐Aminopropyl) triethoxysilane and silver nanoparticles
Abstract
The development of an electrochemical nanoaptasensor to sensing chloramphenicol using a nanocomposite consisting of graphene oxide functionalized with (3‐Aminopropyl) triethoxysilane and silver nanoparticles
In the present research, a nanoaptasensor is proposed for electrochemical measurement of chloramphenicol (CAP). To this purpose, the nanocomposite prepared from graphene oxide and functionalized with (3‐Aminopropyl) triethoxysilane/silver nanoparticles to the abbreviated AgNPs/[NH2–Si]-f-GO, was utilized to modify the glassy carbon electrode (GCE). Furthermore, the modified electrode was also investigated using the electrochemical methods such as electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The AgNPs/[NH2–Si]-f-GO nanocomposite was investigated by UV–Vis spectrophotometry. Fourier transform infrared (FT-IR) spectrometry and transmission electron microscopy (TEM). Moreover, [Fe(CN)6]3-/4 solution in the role of an electrochemical probe was applied. The AgNPs/ [NH2–Si]-f-GO nanocomposite was confirmed as a good layer to covalent immobilization of aptamer (Apt) onto the GCE surface. In this sense, the DPV was used as a sensitive electrochemical technique for the measurement of CAP with an appropriate linear concentration range which was found to be between 10 pM and 0.2 μM and, with a low limit of detection, it equaled 3.3 pM. CAP which was identified in the presence of other usual antibiotics existed in the real samples.
Pd(II) and Pt(II) Metallacycles with Unsymmetrical Ylide: Antiproliferative Effects and Application in Electrocatalytic Oxidation of Methanol
Abstract
Pd(II) and Pt(II) Metallacycles with Unsymmetrical Ylide: Antiproliferative Effects and Application in Electrocatalytic Oxidation of Methanol
New Pd(II) and Pt(II) complexes are described in which the multidentate phosphorus ylides [Ph2P(CH2)nPPh2=C(H)C(O)C6H4‐p‐OCH3] (n=1, (Y1); n=2, (Y2)) act as P,C chelating ligands. The chelating ability of these ligands resulted in the formation of [MBr2{K2(P,C)‐Y1}] (M=Pd (1), Pt (2)); [MBr2{K2(P,C)‐Y2}] (M=Pd (3), Pt (4) complexes, which were investigated using physicochemical techniques. X‐ray diffraction studies of a single crystal of complex 2 confirmed the structure of the five‐membered ring. Owing to the redox activity of phosphorus‐ylide complexes, their electrocatalytic activity for the oxidation of methanol has been studied. All compounds were found to possess the anti‐proliferative potency against MCF‐7 (breast carcinoma), A549 (non‐small lung carcinoma) and AGS (gastric carcinoma) cell lines with average IC50 values in the range of 14.53 to 287.92 μM. In general, the compounds Y1, Y2, 2, and 3 displayed high anticancer activities compared to 1 and 4. The antioxidant activity of the compounds, which was estimated by 1, 1‐diphenyl‐2‐picryl‐hydrazyl (DPPH) free radical scavenging, was moderate to strong with IC50 values in the range 0.18 to 0.59 mg mL−1.
A nano-sized chitosan particle based electrochemical aptasensor for sensitive detection of P. aeruginosa
Abstract
A nano-sized chitosan particle based electrochemical aptasensor for sensitive detection of P. aeruginosa
In this research, a glassy carbon electrode (GCE) was modified with nano-sized chitosan particles (NCs) by the drop-casting method for ultrasensitive detection of Pseudomonas aeruginosa (P. aeruginosa). NCs act as a novel platform for the aptamer-based sensor (aptasensor) for sensitive and simultaneous detection of P. aeruginosa. This system is based on a P. aeruginosa-binding aptamer, which is covalently connected to the surface of the GCE which has been in turn modified by the NC in order to form a sensitive layer and improve the performance of the aptasensor. In order to investigate the conductivity of the aptasensor and its electrochemical properties, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques were used. A low detection limit of 3 CFU mL1 , wide linearity of 101 –107 CFU mL1 for the detection of P. aeruginosa and high sensitivity for the aptasensor, which are obtained under optimized conditions, have been proposed. To detect P. aeruginosa in blood serum samples, the prepared aptasensor was successfully applied. This aptasensor also showed excellent stability with satisfactory electrochemical performance, reproducibility, and selectivity.
Impedimetric ultrasensitive detection of chloramphenicol based on aptamer MIP using a glassy carbon electrode modified by 3-ampy-RGO and silver nanoparticle
Abstract
Impedimetric ultrasensitive detection of chloramphenicol based on aptamer MIP using a glassy carbon electrode modified by 3-ampy-RGO and silver nanoparticle
In this research work, a biosensor with a dual recognition system was fabricated and founded on a combination of aptasensing and the molecular imprinting union of the chloramphenicol (CAP) selective detection. CAP, is an antibiotic, was applied in veterinary and human in order to treat gram-positive and gram-negative infections. It is worth mentioning that CAP residue brings about earnest side effects on human health. According to this, in this sensing system, 3-aminomethyl pyridine functionalized graphene oxide (GO) (3-ampy-RGO) has been coated on the surface of GCE. Afterwards, the silver nanoparticle (AgNPs) was coated on the 3-ampy-RGO/GCE and, then, the CAP complex-amino-aptamer (NH2-Apt[CAP]) was attached to the AgNP/3-ampy-RGO/GCE using a kind of bonding formation of Ag-N. In this sense, it is worth noting that the resorcinol electropolymerization around the complex of aptamer/CAP would confine the complex and, then, retain the aptamer. Following the CAP removal, the MIP cavity, as it was supposed, synergistically acted with that of the embedded aptamer in order to construct a nanohybrid receptor. Interestingly, the double exact property of the molecular imprinting polymers and aptamers led to the superb sensing properties. In the mentioned system it was illustrated that the linear range was from 1.0 pM to 1.0 nM with the detection limit of 0.3 pM; consequently, as observed, it was better than or as good as other similar assays. Moreover, the mentioned system whose activity was observed in the various interferences presence showed great selectivity in detected the CAP. Finally, the designed sensor exhibited outstanding results when applied to detect CAP in milk samples.
Highly sensitive electrochemical determination of 5-fluorouracil using CuNPs/MWCNT/IL/Chit composite modified glassy carbon electrode
Abstract
Highly sensitive electrochemical determination of 5-fluorouracil using CuNPs/MWCNT/IL/Chit composite modified glassy carbon electrode
A fast and facile electrochemical sensor for detection of important anti-cancer drug 5- fluorouracil (5-FU) is fabricated using a copper-nanoparticles decorated multi-walled carbon nanotube and chitosan composite modified electrode. Copper nanoparticles/multi-walled carbon nanotubes/ionic liquid/chitosan modified glassy carbon electrode (CuNPs/MWCNTs/IL/Chit/GCE) prepared by the consecutive coating of MWCNTs/IL/Chit nanocomposite on the GCE, followed by the electrodeposition of copper. Surface characteristics of the modified electrode were studied by scanning electron microscopy (SEM). The electrochemical capability of the fabricated modified electrode for the detection of 5-FU is examined by cyclic voltammetry, differential pulse voltammetry (DPV). The nano Cu decorated MWCNTs/IL/Chit/GCE is found to be efficient for the electrocatalytic oxidation of 5-FU. The peak current of the DPV exhibited a linear relationship against 5-FU over a wide concentration range of 1-110 µM with a low detection limit (0.15 µM). Additional, the sensor was successfully applied in biological fluid sample analysis.
Development of an electrochemical aptasensor based on the gold nanorods and its application for detection of aflatoxin B1 in rice and blood serum samples
Abstract
Development of an electrochemical aptasensor based on the gold nanorods and its application for detection of aflatoxin B1 in rice and blood serum samples
Aflatoxins are a group of fungal mycotoxins produced mainly by molds; e.g., Aspergillus flavus and Aspergillus parasiticus. Among Aflatoxins, Aflatoxin B1 (AFB1) is the most toxic one. Therefore, there is a prompt need for determination of AFB1 in food products. This paper reports an electrochemical aptasensor for accurate determination of AFB1, which was constructed using gold nanorod sensing interface and aptamer as a specific recognition element. The synthesized gold nanorod was characterized by transmission electron microscopy, and the electrochemical behavior of fabricated aptasensor was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Under optimized conditions, the detection limit of the proposed aptasensor was 0.3 pM with dynamic range of 1.0 pM – 0.25 nM. This aptasensor represents a remarkable improvement in terms of sensitivity, selectivity, reproducibility and stability compared to the other methods for the determination of AFB1. This proposed sensor was successfully applied for the analysis of AFB1 in rice and blood serum samples.
The potentiality of graphene quantum dots functionalized by nitrogen and thiol-doped (GQDs-N-S) to stabilize the antibodies in designing of human chorionic gonadotropin immunosensor
Abstract
The potentiality of graphene quantum dots functionalized by nitrogen and thiol-doped (GQDs-N-S) to stabilize the antibodies in designing of human chorionic gonadotropin immunosensor
In this study, for the first time, a simple immunosensor for ultrasensitive recognition of human chorionic gonadotropin (HCG) in serum samples was fabricated using a simple approach. In this method, a low-cost, sensitive immunosensor was made based on QDs-N-S/Au nanoparticles (NPs) modified screen-printed carbon electrode (SPCE). It seems that QDs-N-S/AuNPs/ antibody as a biocomposite can be a good choice for development as an impressive immunosensor. In modifying the proposed immunosensor, the length of the process was reduced and the use of other substrates was eliminated. The pH and incubation time were optimized as two important parameters. Under the optimal conditions at modified SPCE, a linear communication in the range of 0.1 to 125 pg mL−1 and the detection limit of 12.5 fg mL−1 were obtained. The present procedure was utilized to the detection of HCG in real samples with the desirable results
Ti(IV) ion-imprinted polymer as a new selective sorbent for extraction and pre-concentration of trace amounts of titanium ions in different samples
Abstract
Ti(IV) ion-imprinted polymer as a new selective sorbent for extraction and pre-concentration of trace amounts of titanium ions in different samples
In this paper, a novel, simple, selective and effective solid phase extraction method based on ion-imprinted polymer (IIP) technology and flame atomic absorption spectrometry (FAAS) for separation and pre-concentration of trace amounts of titanium (IV) ions was reportd. It was obtained by precipitation polymerisation by using 2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxychromen-4-one titanium (IV) complex abbrivated as Ti(IV)-(morin), as the template molecule. After polymerisation, leaching the polymer in HNO3 (50% (v/v) solution caused formation cavities in the polymer. Characterisation studies of the Ti(IV)-imprinted polymer (Ti-IP) was performed by FT-IR, UV-Vis and scanning electron microscopy- energy-dispersive X-ray spectroscopy (SEM-EDS) techniques and then, the effective factors on extraction were optimised. A sensitive response to Ti(IV) within a concentration range between 0.01 and 4.0 μg mL−1 was achieved under the optimum conditions. A total of 10.0 ng mL−1 and 80.0 mg g−1 were obtained as limit of detection (LOD, 3Sb/m) and maximum adsorption capacity, respectively. The relative standard deviation (RSD) for eight replicates detections of 0.2 μg mL−1 of Ti(IV) was found to be 2.8%. By this method, pre-concentration factor (PF) of 100 was obtained. Successfully applying this method in the water and standard samples, reasonable results were obtained for the extraction and pre-concentration of the titanium ions.
Fabrication of novel metanil yellow/multi wall carbon nanotubes-chitosan/ modified glassy carbon electrode and its application for sensitive determination of persulfate
Abstract
Fabrication of novel metanil yellow/multi wall carbon nanotubes-chitosan/ modified glassy carbon electrode and its application for sensitive determination of persulfate
A new intensely-sensitive amperometric sensor applied for the rapid and accurate detection of persulfate and based on the modification of glassy carbon electrode (GCE) by multi-wall carbon nanotubes-chitosan (MWCNTs- Chit) nanocomposite and metanil yellow (MY) is fabricated. In this sense, MY which can be used as an excellent redox mediator can also catalyze the reduction of persulfate. The presence of MWCNTs-Chit nanocomposite can provide associated sites for the electrode position of MY on the electrode surface due to the high surface area. Moreover, it can also accelerate the rate of electron-transfer between MY film and the electrode due to its good catalytic capability. Combining these materials as modifiers caused the prepared MY/MWCNTs-Chit/GC electrode to display a linear amperometric respond to the persulfate concentration from 100 nM to 1.0 mM with a sensitivity of 860.1 nAnM−1 and a limit of detection (S/N=3) of 0.03 μM. The proposed sensor is successfully applied for the determination of persulfate in river water samples with satisfactory results.
An electrochemical tyrosinamide aptasensor using a glassy carbon electrode modified by N-acetyl-L-cysteine-capped Ag-In-S QDs
Abstract
An electrochemical tyrosinamide aptasensor using a glassy carbon electrode modified by N-acetyl-L-cysteine-capped Ag-In-S QDs
This paper reports an aptamer-based green approach for the electrochemical evaluation of tyrosinamide (Tyr- NH2). In this regard, at the first step, an aqueous synthetic strategy for preparing N-acetyl-L-cysteine (NAC)- capped Ag-In-S (AIS) quantum dots (QDs) with bright yellow/orange emission was developed. The conjugation of AIS QDs to NAC-biomolecules provides opportunities for using them as luminescent contrast agents for living cell tracking and labeling or sensing studies. In the next step, the design stage of the aptasensor, the glassy carbon electrode (GCE) was modified with the AIS QDs and then the Tyr-NH2 special aptamer, which has an amine group at its end, interacts with silver and indium ions at the surface of the AIS QDs and through the formation of covalent bonding of AgeN and IneN, attaches to the GCE surface modified with the AIS QDs. In this approach, for the first time, NAC-capped AIS QDs have been used to modify the electrode surface in the aptamerbased electrochemical sensor. The response changes of the [Fe(CN)6]4−/3− as redox probe, during the modification of GCE surface, the fabrication and assessment of proposed aptasensing, using the cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy were recorded. The designed aptasensor for the Tyr-NH2 evaluation showed good linearity from 0.01 to 2.81 nM and 2.81–10.81 nM, and low detection limit of 3.34 pM. The obtained results of the stability, reproducibility and selectivity investigations implying that the reported aptasensor as the first aptamer-based electrochemical assay for Tyr-NH2, can be reliable for the determination of Tyr-NH2 in serum samples.
Developing a four-dimensional voltammetry as a powerful electroanalytical methodology for simultaneous determination of three colorants in the presence of an uncalibrated interference
Abstract
Developing a four-dimensional voltammetry as a powerful electroanalytical methodology for simultaneous determination of three colorants in the presence of an uncalibrated interference
This paper reports an aptamer-based green approach for the electrochemical evaluation of tyrosinamide (Tyr- NH2). In this regard, at the first step, an aqueous synthetic strategy for preparing N-acetyl-L-cysteine (NAC)- capped Ag-In-S (AIS) quantum dots (QDs) with bright yellow/orange emission was developed. The conjugation of AIS QDs to NAC-biomolecules provides opportunities for using them as luminescent contrast agents for living cell tracking and labeling or sensing studies. In the next step, the design stage of the aptasensor, the glassy carbon electrode (GCE) was modified with the AIS QDs and then the Tyr-NH2 special aptamer, which has an amine group at its end, interacts with silver and indium ions at the surface of the AIS QDs and through the formation of covalent bonding of AgeN and IneN, attaches to the GCE surface modified with the AIS QDs. In this approach, for the first time, NAC-capped AIS QDs have been used to modify the electrode surface in the aptamerbased electrochemical sensor. The response changes of the [Fe(CN)6]4−/3− as redox probe, during the modification of GCE surface, the fabrication and assessment of proposed aptasensing, using the cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy were recorded. The designed aptasensor for the Tyr-NH2 evaluation showed good linearity from 0.01 to 2.81 nM and 2.81–10.81 nM, and low detection limit of 3.34 pM. The obtained results of the stability, reproducibility and selectivity investigations implying that the reported aptasensor as the first aptamer-based electrochemical assay for Tyr-NH2, can be reliable for the determination of Tyr-NH2 in serum samples.
Exploring the binding mechanism of saccharin and sodium saccharin to promoter of human p53 gene by theoretical and experimental methods
Abstract
Exploring the binding mechanism of saccharin and sodium saccharin to promoter of human p53 gene by theoretical and experimental methods
In the past few decades, extensive discussions have been on the impact of artificial sweeteners on the risk of cancer. The present study aimed to evaluate the interaction of saccharin (SA) and sodium saccharin (SSA) with the promoter of the human p53 gene. The binding ability was assessed using the spectroscopic technique, molecular docking and molecular dynamics (MD) simulation methods. Free energy of binding has been calculated using Molecular Mechanics/Poisson–Boltzmann Surface Area (MM/PBSA) method. Fluorescence spectra of mentioned gene with concentration profiles of SA and SSA were obtained in a physiological condition. A gradual increase without any significant spectral shift in the fluorescence intensity of around 350 nm was evident, indicating the presence of an interaction between both compounds and gene. The docking results showed that both compounds were susceptible to bind to 50 -DG56DG57-30 nucleotide sequence of gene. Furthermore, the MD simulation demonstrated that the binding positions for SA and SSA were 50 -A1T3T4-30 and 50 -G44T45-30 sequences of gene, respectively. The binding of these sweeteners to gene made significant conformational changes to the DNA structure. Hydrogen and hydrophobic interactions are the major forces in complexes stability. Through the groove binding mode, the non-interactive DNA-binding nature of SSA and SA has been demonstrated by the results of spectrofluorometric and molecular modeling. This study could provide valuable insight into the binding mechanism of SA and its salt with p53 gene promoter as macromolecule at the molecular level in atomistic details. This work can contribute to the possibility of the potential hazard of carcinogenicity of this sweetener and to design and apply new and safer artificial sweeteners.
Preparation of modified glassy carbon electrode by the use of titanium oxide, copper and palladium nanoparticles and its application for the electrocatalytic and photelectrocatalytic reduction of hydrogen peroxide
Abstract
Preparation of modified glassy carbon electrode by the use of titanium oxide, copper and palladium nanoparticles and its application for the electrocatalytic and photelectrocatalytic reduction of hydrogen peroxide
A new electrochemical sensor for hydrogen peroxide (H2O2) determination was fabricated based on less expensive and simple layer-by-layer method. The morphological and elemental characteristics of palladium, copper and titanium oxide nanoparticles modified glassy carbon electrode (GCE) were examined using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), respectively. The electrochemical behaviors of H2O2 on constructed sensor were investigated by cyclic voltammetry and amperometry techniques. By integration of the palladium, copper and titanium oxide nanoparticles into the nanocomposite, the constructed nanocomposite illustrated good synergistic effect in reduction of H2O2, thereby resulting in the higher cathodic peak current and very reduced over potential. The sensor displays a fast response time less than 2 s with a linear range from 0.05 µM to 0.1 M and detection limit of 16.0 nM (S/N=3). Moreover, the photoelectrocatalytic capability of the proposed modified electrode was explored in dark and under light irradiation conditions. The catalytic current significantly increased under illumination condition and it comes back to its original value by turning off the light irradiation. This result indicates the stable photo-induced catalytic behavior of the constructed sensor. The resulting sensor was successfully used to detection of hydrogen peroxide in real samples.
An electrochemical aptasensor for streptomycin based on covalent attachment of the aptamer onto a mesoporous silica thin film-coated gold electrode
Abstract
An electrochemical aptasensor for streptomycin based on covalent attachment of the aptamer onto a mesoporous silica thin film-coated gold electrode
An electrochemical method is described for the determination of streptomycin (STR). It is making use of a gold electrode coated with a thin mesoporous silica film (MSF). In addition, silver nanoparticles were coated on the MSF to increase the surface area, to bind a large amount of aptamer (Apt), and to improve the electrical conductivity. In the presence of STR, it will bind to the Apt and hinder the diffusion of the redox probe hexacyanoferrate through the nanochannels of the mesoporous film. The aptasensor, best operated at a working potential of 0.22 V (vs. Ag/AgCl) has a linear response in the 1 fg.mL−1 to 6.2 ng.mL−1 STR concentration range. The detection limit is 0.33 fg.mL−1 . The assay was successfully validated by analyzing spiked samples of milk and blood serum.
Synthesis, characterization, anticancer properties and theoretical study of asymmetrical Cd(II)–N2-Schiff base complexes
Abstract
Synthesis, characterization, anticancer properties and theoretical study of asymmetrical Cd(II)–N2-Schiff base complexes
In this study, synthesis, characterization and anticancer properties of four cadmium(II) complexes of a new asymmetrical bidentate Schiff base ligand (abbreviated as L) with a CdLX2 (X = Cl−, Br−, I− and SCN−) general formula are reported. The ligand and its complexes were characterized by elemental analysis, molar conductance, UV–Vis, FT-IR, 1H NMR and 13C NMR spectra. Coordination of the ligand was confirmed by consistent changes in FT-IR and NMR spectra when compared with the spectra of free ligand. Redox properties of ligand and complexes were investigated by the electrochemical method, cyclic voltammetry. Also, changes in the cathodic and anodic peaks potentials of complexes regarding free ligand, confirm synthesis of complexes. All complexes correspond to Cd(II)/Cd(0) system show one pair anodic and cathodic peaks. The density function theory calculations are used to investigate the electronic structures of the ligand and its complexes. In vitro anticancer activity of ligand and complexes was studied on cancer cells lines HT29 and A549. Obtained data confirmed the potent cytotoxic activity in the chloro and bromo substituted Cd(II) complexes when compared with free ligand, control sample and other Cd(II) compounds. The IC50 values for ligand and complexes were approximately less than 0.1 mg mL−1.
Development of electrochemical sensor based on molecularly imprinted copolymer for detection of nitrofurantoin
Abstract
Development of electrochemical sensor based on molecularly imprinted copolymer for detection of nitrofurantoin
The present study aimed to identify and analyze how an imprinted molecularly sensor was used for a direct determination of nitrofurantoin (NFT). The polymerization was directly performed on the surface of glassy carbon electrode by m-dihydroxybenzene and o-aminophenol as monomers. In this regard, the most fundamental issue to be noticed was the special porous forms which, after being washed, were obtained for the NFT molecule. Accordingly, great selectivity and high sensitivity to detect NFT were observed. The proposed system showed good linearity ranging from 0.001 to 0.05 and 0.1 to 1.0 µM, with a detection limit of 0.3 nM. Finally, it should also be noted that the proposed sensor was very selective and sensitive for the detection of NFT in the real serum samples.
Development of Electrochemical Sensor Based on Glassy Carbon Electrode Modified with a Molecularly Imprinted Copolymer and its Application for Detection of Repaglinide
Abstract
Development of Electrochemical Sensor Based on Glassy Carbon Electrode Modified with a Molecularly Imprinted Copolymer and its Application for Detection of Repaglinide
At the present study, we have reported a new sensor based on immobilized molecularly imprinted polymer on the surface of a glassy carbon electrode (GCE) through electro polymerization of o‐Dihydroxybenzene (o‐DB) and o‐phenylenediamine (o‐PD) as monomers for direct determination of repaglinide (RPG) as target molecule. RPG is a new generation of oral anti‐diabetic drugs that has a rapid onset of action and short half‐life of approximately 1 h. So developing a controlled system with good sensitivity and selectivity is required to eliminate its adverse effects. Under the optimized conditions, the proposed sensor showed a good selectivity to detect RPG among compounds with similar structure and properties with RPG. The linear range for analysis were 0.005–1.0 μM and detection limit 1.8 nM was achieved. Furthermore, the experimental results showed that the proposed sensor was highly selective and sensitive to detect RPG in real samples such as blood serum, urine and RPG tablet.
A glassy carbon electrode with electrodeposited silver nanoparticles for aptamer based voltammetric determination of trinitrotoluene using riboflavin as a redox probe
Abstract
A glassy carbon electrode with electrodeposited silver nanoparticles for aptamer based voltammetric determination of trinitrotoluene using riboflavin as a redox probe
An electrochemical nanoaptasensor is described that is based on the use of a glassy carbon electrode (GCE) modified with electrodeposited silver nanoparticles (AgNPs). An aptamer (Apt) against trinitrotoluene (TNT) was then immobilized on the AgNPs. The addition of TNT to the modified GCE leads to decrease in peak current (typically measured at a potential of −0.45 V vs. Ag/AgCl) of riboflavin which acts as an electrochemical probe. Even small changes in the surface (as induced by binding of Apt to TNT) alter the interfacial properties. As a result, the LOD is lowered to 33 aM, and the dynamic range extends from 0.1 fM to 10 μM without sacrificing specificity
Applicability of AuNPs@N-GQDs nanocomposite in the modeling of the amplified electrochemical Ibuprofen aptasensing assay by monitoring of riboflavin
Abstract
Applicability of AuNPs@N-GQDs nanocomposite in the modeling of the amplified electrochemical Ibuprofen aptasensing assay by monitoring of riboflavin
Here, an ultrasensitive and low-cost electrochemical aptasensing assay is developed based on the applicability of a fabricated nanocomposite from nitrogen-doped graphene quantum dots (N-GQDs) and gold nanoparticles (AuNPs). A modified glassy carbon electrode (GCE) with the AuNPs@N-GQDs nanocomposite (AuNPs@ N-GQDs/GCE) as an efficient platform has some unique properties such as high surface area and electrical conductivity. Furthermore, the prepared platformis capable of more loading of aptamer (Apt)molecules as a biological recognition element of Ibuprofen (IBP) on the modified electrode surface. It is noteworthy that in this study, riboflavin (RF) as a universal green probe is used for the first time for electrochemical detection of IBP. According to the proposed strategy and under the optimum condition, the unprecedented detection limit (LOD) of this assay (33.33 aM) is lower than previously reported analytical methods. The results demonstrate the ability of the nanocomposite for designing of the aptasensor, integrated within the electrode format, to cheaper and simpler detection of the IBP with a specificity and sensitivity sufficient for analysis in real samples. It seems that the proposed strategy based on the AuNPs@N-GQDs nanocomposite can be expanded to other nanomaterials. So, this is expected to have promising implications in the design of electrochemical sensors or biosensors for the detection of various targets.
An electrochemical chlorpyrifos aptasensor based on the use of a glassy carbon electrode modified with an electropolymerized aptamer-imprinted polymer and gold nanorods
Abstract
An electrochemical chlorpyrifos aptasensor based on the use of a glassy carbon electrode modified with an electropolymerized aptamer-imprinted polymer and gold nanorods
A highly selective and sensitive aptasensor is described for voltammetric determination of the pesticide chlorpyrifos (CPS). The sensor was constructed by modifying a glassy carbon electrode (GCE) with gold nanorods and a polymer that was molecularly imprinted with an aptamer against CPS. This results in double specific recognition. Under optimal conditions and a working potential as low as 0.22 V (vs. Ag/AgCl), the nanotools has a dynamic range that covers the 1.0 fM - 0.4 pM CPS concentration range, and the detection limit is 0.35 fM. This is lower than any of the previously reported methods. This MIP-aptasensor is selective over structural analogs, stable, and adequately reproducible. It was successfully applied to the determination of CPS in spiked food samples.
A novel aptasensor based on gold nanorods/ZnS QDs-modified electrode for evaluation of streptomycin antibiotic
Abstract
A novel aptasensor based on gold nanorods/ZnS QDs-modified electrode for evaluation of streptomycin antibiotic
In this study, a simple and effective strategy was developed for specific detection of streptomycin (STR) antibiotic. At first, in this strategy, glassy carbon electrode (GCE) was covered by thiourea capped-ZnS QDs and gold nanorods (AuNRs) for the construction of a sensing interface for thiolated aptamer immobilization. Subsequently, the STR thiol-aptamer was covalently attached on the AuNRs/thiourea capped-ZnS QDs/GCE via Au–S bond formation. Morphology of the modified electrode was characterized via emission scanning electron microscopy (FE-SEM) technique. The proposed system showed good linearity ranging from 1 fg mL1 to 1.111 pg mL1 and 1.111 pg mL1 to 11.1111 ng mL1 , with a detection limit of 0.35 fg mL1 . Furthermore, this methodology was also applied to evaluate STR in milk and serum samples, indicating the feasibility of the application of aptasensor analysis for STR detection. The presented system, in presence of different interferences, indicated good selectivity in detecting the STR. Our study provides a facile and low-cost method for designing aptamer-based sensors toward the evaluation of other antibiotics if the specific aptamer is available.
MATLAB in electrochemistry: A review
Abstract
MATLAB in electrochemistry: A review
MATLAB (MATrix LABoratory) is a multi-paradigm numerical computing environment and fourth-generation programming language. MATLAB allows matrix manipulations, plotting of functions and data, implementation of algorithms, creation of user interfaces and interfacing with programs written in other languages, including C, C++, Java, Fortran and Python. Electrochemistry is a branch of chemistry that studies the relationship between electricity, as a measurable and quantitative phenomenon, and identifiable chemical change, with either electricity considered an outcome of a particular chemical change or vice versa. MATLAB has obtained a wide range of applications in different fields of science and electrochemists are also using it for solving their problems which can help them to obtain more quantitative and qualitative information about systems under their studies. In this review, we are going to cast a look on different applications of MATLAB in electrochemistry and for each section, a number of selected articles published in the literature will be discussed and finally, the results will be summarized and concluded.
A novel electrochemical sensor based on electrode modi ed with gold fi nanoparticles and molecularly imprinted polymer for rapid determination of trazosin
Abstract
A novel electrochemical sensor based on electrode modi ed with gold fi nanoparticles and molecularly imprinted polymer for rapid determination of trazosin
A novel molecularly imprinted polymer sensor for fast and direct determination of trazosine (TR) was studied. The voltammetric sensor based on molecularly imprinted polymer (MIP) with disposable gold nanoparticles modi ed screen printed carbon electrode (MIP/AuNPs/SPCE) is developed for the determination of TR. Under fi the optimum conditions, the peak current of the sensor and TR concentration showed a good linear relationship over the range from 2.0 to 250.0 M, with a low detection limit (S/N = 3) of 0.3 M. The modi ed electrode μ μ fi demonstrated good electrocatalytic properties toward the oxidation of TR. This sensor selectively detected TR even in the presence of high concentration of similar compounds and MIP/AuNPs/SPCE was also con rmed fi successfully for the determination of TR in the various real samples including human blood serum, urine and trazosin tablet.
An aptasensor for voltammetric and impedimetric determination of cocaine based on a glassy carbon electrode modified with platinum nanoparticles and using rutin as a redox probe
Abstract
An aptasensor for voltammetric and impedimetric determination of cocaine based on a glassy carbon electrode modified with platinum nanoparticles and using rutin as a redox probe
We describe a method for the determination of cocaine that is based on a glassy carbon electrode modified with a nanocomposite consisting of multiwalled carbon nanotubes, an ionic liquid, and chitosan. The electrode was made cocaineresponsive by immobilizing a cocaine-specific aptamer and platinum nanoparticles (PtNPs) on the modified electrode. The use of PtNPs resulted in the acceleration of the electron transfer kinetics of the reduction of the redox probe rutin and enhances sensitivity. The sensor, best operated at a working voltage of 260 mV vs. Ag/AgCl, has a linear response to cocaine in the 1 nM to 11 μM concentration range, and the detection limit is 100 pM (at an S/N ratio of 3). We think this strategy to represent a promising platform for the sensitive and selective determination of cocaine. The sensor is adequately stable and was successfully applied to the determination of cocaine in spiked serum.
Synthesis, characterization, anticancer properties and theoretical study of asymmetrical Cd(II)eN2-Schiff base complexes
Abstract
Synthesis, characterization, anticancer properties and theoretical study of asymmetrical Cd(II)eN2-Schiff base complexes
In this study, synthesis, characterization and anticancer properties of four cadmium(II) complexes of a new asymmetrical bidentate Schiff base ligand (abbreviated as L) with a CdLX2 (X ¼Cl-, Br-, I- and SCN-) general formula are reported. The ligand and its complexes were characterized by elemental analysis, molar conductance, UVeVis, FT-IR, 1H NMR and 13C NMR spectra. Coordination of the ligand was confirmed by consistent changes in FT-IR and NMR spectra when compared with the spectra of free ligand. Redox properties of ligand and complexes were investigated by the electrochemical method, cyclic voltammetry. Also, changes in the cathodic and anodic peaks potentials of complexes regarding free ligand, confirm synthesis of complexes. All complexes correspond to Cd(II)/Cd(0) system show one pair anodic and cathodic peaks. The density function theory calculations are used to investigate the electronic structures of the ligand and its complexes. In vitro anticancer activity of ligand and complexes was studied on cancer cells lines HT29 and A549. Obtained data confirmed the potent cytotoxic activity in the chloro and bromo substituted Cd(II) complexes when compared with free ligand, control sample and other Cd(II) compounds. The IC50 values for ligand and complexes were approximately less than 0.1mgmL-1.
Dual detection of Malation and Hg (II) byfluorescence switching of graphene quantum dots
Abstract
Dual detection of Malation and Hg (II) byfluorescence switching of graphene quantum dots
The present study investigates sensitive and selective“off–on” method to analyze and detect mercury ions (Hg 2+ ) and Malation pesticide using graphene quantum dots (GQDs) as a new fluorescent (FL) probe. When GQDs are present, Hg 2+ cations are capable of being coordinated on the GQD surface by their negatively charged surface. The process of absorption occurs using electrostatic interactions. Hence, the FL of the GQDs would be remarkably quenched (turn-off) at 463 nm for 1μMHg2+ as a result of FL charge transfer. Nevertheless, when 40 μM of Malation is added to the GQDs-Hg 2+ solution, the FL of the GQDs enhances significantly at 463 nm (turnon), since Hg 2+ is combined with SR- group in the Malation rather than with the GQDs in the aqueous solution. Instead of the weak electrostatic interaction, a strong metal-thiol bond interaction is formed between Hg 2+ and Malation and an enhancement in the FL of GQDs is observed. Finally, acceptable linearity for Hg 2+ and Malation detection is obtained in the concentration ranges of 1–10μM and 10–80 for Hg 2+ and linear range of 80–120μM for Malation with an LOD of 0.5 μM and R 2 = 0.99.
Designing of some platinum or palladium-based nanoalloys as effective electrocatalysts for methanol oxidation reaction
Abstract
Designing of some platinum or palladium-based nanoalloys as effective electrocatalysts for methanol oxidation reaction
Nano alloys contain noble metal nanostructures exhibit a wide theoretical and experimental interest in the field of fuel cells. Hard endeavors have been enhanced to improve the catalytic performance and minimize the usage of precious metals by alloying them with non-precious ones. Formation of bimetallic and trimetallic noble metal alloys with well-designed structures provide the opportunity to reach this goal. In this study, we first discuss the synthesis of noble metal alloy nanostructured thin films such as PtCu, PdCu, PtCu/reduced-graphene oxide (RGO), PdCu/RGO, PtCo, PtCo/RGO, PtPdCu and PtPdCu/RGO viaa simple reduction of organometallic precursors including [PtCl2(cod)] and [PdCl2(cod)], (cod ¼ cis, cis-1,5-cyclooctadiene), in the presence of [Cu(acac)2] and [Co(acac)3](acac ¼acetylacetonate) at oil/water interface and room temperature, including nanoparticles and nanosheets. Then the effects of the well-defined nanostructures on the improved electrochemical properties are outlined. Finally, we conclude that these nonprecious bi and trimetallic alloy nanostructured thin films have better electrocatalytic performance than Pt monometallic thin films and other Pt nanostructures due to the geometric, electronic and stabilizer effect.
Using Boehmite Nanoparticles as an Undercoat, and Riboflavin as a Redox Probe for Immunosensor Designing: Ultrasensitive Detection of Hepatitis C Virus Core Antigen
Abstract
Using Boehmite Nanoparticles as an Undercoat, and Riboflavin as a Redox Probe for Immunosensor Designing: Ultrasensitive Detection of Hepatitis C Virus Core Antigen
In this study, a label -free electrochemical immunosensor for ultrasensitive detection of Hepatitis C virus core antigen in serum samples was fabricated using a simple approach. In this method, a low- cost and sensitive immunosensor was fabricated based on a boehmite nanoparticles (BNPs) modified glassy carbon. The BNPs provide a specific platform with an increased surface area which is capable of loading more antibody molecules as a receptor element of Hepatitis C virus core antigen on the electrode surface. It seems that BNP/ antibody conjugate may be an ideal platform for the development of an efficient immunosensor. It is worth noting that the proposed nanoimmunosensor combines the advantages of the elimination of another substrates in modifying the electrode and reducing the length of the modifying process. The experimental parameters, such as pH and incubation of time were optimized. Und er the optimal conditions for modified glassy carbon electrode, a linear relationship was realized in the range of 0.08- 110 pg ml -1 , with the detection limit of 10 fg ml -1 . The proposed method was applied to the determination of Hepatitis C virus core antigen in serum samples with the desirable results.
Applicability of the Dendrimer-quantum Dot (Den- QD) Bioconjugate as a Novel Nanocomposite for Signal Amplification in the Fabrication of Cocaine Aptasensor
Abstract
Applicability of the Dendrimer-quantum Dot (Den- QD) Bioconjugate as a Novel Nanocomposite for Signal Amplification in the Fabrication of Cocaine Aptasensor
A selective aptasensor was developed using the electrochemical transduction method for the ultrasensitive detection of cocaine. Inthis method, dendrimer-quantum dot (Den- QD) bioconjugate was utilized as a specific nanocomposite to efficiently fabricate the aptasensor. CdTe QD, which carries highly significant properties, was immobilized on the surface of a glassy carbon electrode (GCE), and polyamidoamine (PAMAM) dendrimer (Den) was covalently attached to the carboxyl-terminated surface of the CdTe QDs. This clever combination of QD and Den provides a highly stable matrix for the increased loading of aptamer (Apt)as a cocaine molecular receptor via covalent attachment. The Apt was functionalized with AuNPs leading to the amplification of the electrochemical signal. In this study, upon the incubation of cocaine on the aptasensor surface, the peak current of the redox probe decreased due to the hindered electron transfer reaction on the sensing surface. This study shows that the proposed aptasensor can detect cocaine by electrochemical impedance spectroscopy (EIS) technique at a linear range (5.00 10 -3 -6.00 nM) and a capability of detection down to 1.60 pM. The excellent specificity of this sensing system is demonstrated using some common analgesic drugs, and finally, the proposed aptasensor was successfully used to measure cocaine in the human serum sample. The proposed methodology may hold great promise for the design of other aptasensors and immunosensors based on the use of the Den-QD bioconjugate as a nanocomposite with high performance.
Polymerization of graphene oxide nanosheet by using of aminoclay: Electrocatalytic activity of its platinum nanohybrids
Abstract
Polymerization of graphene oxide nanosheet by using of aminoclay: Electrocatalytic activity of its platinum nanohybrids
This study describes the polymerization of graphene oxide (GO) nanosheet to reduced‐GO‐aminoclay (RGC) by covalent functionalization of chemically reactive epoxy groups on the basal planes of GO with amine groups of magnesium phyllosilicate clay (known as aminoclay). The resulting RGC sheets were characterized and applied to support platinum nanostructures at toluene/water interface. Pt nanoparticles (NPs) with diameters about several nanometers were adhered to RGC sheets by chemical reduction of [PtCl2(cod)] (cod = cis,cis‐1,5‐ cyclooctadiene) complex. Catalytic activity of Pt NPs thin films were investigated in the methanol oxidation reaction. Cyclic voltammetry results exhibit that the Pt/reduced‐GO (RGO) and Pt/RGC thin films showed improved catalytic activity in methanol oxidation reaction in comparison to other Pt NPs thin films, demonstrating that the prepared Pt/RGO and Pt/RGC thin films are promising catalysts for direct methanol fuel cell.
Facile synthesis of PtSnZn nanosheet thin film at oil–water interface by use of organometallic complexes: An efficient catalyst for methanol oxidation and p‐nitrophenol reduction reactions
Abstract
Facile synthesis of PtSnZn nanosheet thin film at oil–water interface by use of organometallic complexes: An efficient catalyst for methanol oxidation and p‐nitrophenol reduction reactions
PtSnZn nanosheet thin film with stable and high activity towards methanol electro‐oxidation was synthesized via a simple reduction of organometallic precursors including [PtCl2(cod)] (cod = cis,cis‐1,5‐cyclooctadiene) and [Sn(CH3)4] complexes, in the presence of [Zn(acac)2] (acac = acetylacetonate) complex at toluene–water interface. Catalytic activities of PtSnZn nanosheets were investigated in the p‐nitrophenol (p‐Nip) reduction and methanol oxidation reactions. The obtained results demonstrate that PtSnZn nanosheets exhibit a good electrocatalytic performance for methanol oxidation reaction, the catalytic activity of the PtSnZn nanosheets being at least 3.5 times higher than that of Pt nanoparticle thin film. Also, the apparent rate constant obtained for p‐Nip reduction with the PtSnZn nanosheets is at least 2.3 times higher than that for Pt nanoparticle thin film due to the appropriate interaction between platinum, tin and zinc metals and geometric properties of PtSnZn nanosheet thin film. Nanosheets are highly favourable for superior catalytic performances due to their geometric properties. A facile and efficient route was used to synthesize trimetallic alloy thin film at oil–water interface.
Application of ion-imprinted polymer synthesized by precipitation polymerization as an efficient and selective sorbent for separation and pre-concentration of chromium ions from some real samples
Abstract
Application of ion-imprinted polymer synthesized by precipitation polymerization as an efficient and selective sorbent for separation and pre-concentration of chromium ions from some real samples
In this study, a new Cr(III)-imprinted polymer (Cr(III)-IIP) is prepared from CrCl3·6H2O, methacrylic acid functional monomer, ethyleneglycoldimethacrylate cross-linking agent, 2,2ʹ-azobisisobutyronitrile radical initiator and 2,2-(azanediylbis (ethane-2,1-diyl))bis(isoindoline-1,3-dione) ligand. To obtain the maximum adsorption capacity, the optimum condition was studied through pH, type and concentration of eluent, IIP weight, sample volume as well as the adsorption and desorption times. The Cr(III) ion content was determined via flame atomic absorption spectrometer. In optimum conditions, the adsorption capacity of the IIP for Cr(III) was obtained to be 74.65 mg g−1, using 50 mg of IIP and the initial pH solution of 3.0. Both the adsorption and desorption times for quantitative analyses of Cr(III) ions were 15 and 5 min; respectively. After elution of the adsorbed ions by 3 mL of 4 mol L−1 HNO3 aqueous solution, the established IIP-based SPE procedure provides a reasonable pre-concentration factor of 100. The IIP-based pre-concentration method provides a low detection limit of 1.7 μg L−1 with good repeatability (RSD = 3.22%). Reusability studies confirmed that synthesis IIP is reusable and recoverable up to six cycles. According to the selectivity experiments, it was concluded that the prepared sorbent possesses more affinity toward Cr(III) ions than other ions such as Al3+, Pb2+, Cu2+, Mn2+, Fe2+, Zn2+, and Ni2+ ions. To evaluate the potential applicability of the proposed separation method, the pre-concentration and determination of trace amounts of Cr(III) were performed successfully in food samples with complex matrices, a bestial sample (i.e. cow liver) and an herbal product (i.e., broccoli) as real samples.
Designing an electrochemical aptasensor based on immobilization of the aptamer onto nanocomposite for detection of the streptomycin antibiotic
Abstract
Designing an electrochemical aptasensor based on immobilization of the aptamer onto nanocomposite for detection of the streptomycin antibiotic
Streptomycin (STR), an aminoglycoside antibiotic, was used in human and veterinary to treat gram-negative infections. STR residue causes serious side effects on human health. Accordingly, to achieve a novel and sensitive method for detection of STR, we attempted to develop electrochemical sensing system based on graphene quantum dots (GQDs) functionalized with amine (eNH) and thiol (eSH) groups (GQDs-N-S) as the promising newest carbon-based nanomaterial. In this sensing system, gold nanoparticle (AuNPs) was deposited on the GCE surface. Then GQDs-N-S was coated on the AuNPs/GCE surface. After, the silver nanoparticle (AgNPs) coated on the GQDs-N-S/AuNPs/GCE. Finally, the STR thiol-aptamer (SH-Apt) was covalently attached on the AgNPs/ GQDs-N-S/AuNPs/GCE via bonding formation of AgeS. This system showed linear range from 0.01 pg·mL−1 to 812.21 pg·mL−1 with limit of detection of 0.0033 pg·mL−1 ; it was as good as or better than other similar assays, and also the proposed system, in the presence of different interferences, displayed good selectivity in detecting STR. The proposed aptasensor showed excellent results in quantitatively the detection of STR in serum samples.
Impedimetric detection of cocaine by using an aptamer attached to a screen printed electrode modified with a dendrimer/silver nanoparticle nanocomposite
Abstract
Impedimetric detection of cocaine by using an aptamer attached to a screen printed electrode modified with a dendrimer/silver nanoparticle nanocomposite
The authors describe a highly sensitive method for the aptamer (Apt) based impedimetric determination of cocaine. The surface of a screen-printed electrode (SPE) was modified with a nanocomposite of dendrimer and silver nanoparticles (AgNPs). The cocaine-binding Apt was attached to a dendrimer/AgNP/SPE surface, forming a sensitive layer for the determination of cocaine. The incubation with the analyte resulted in the formation of a cocaine/Apt complex on the electrode surface. As a consequence, folding and conformational change in the aptamer structure was induced, this resulting in a change in the impedimetric signal. The aptaassay exhibits highly efficient sensing characteristics with a good linearity of 1 fmol L −1to 100 nmol L−1(with two linear ranges) and a limit of detection (LOD) of 333 amol L−1 . Its excellent specificity and high sensitivity suggest that this kind of aptamer-based assay may be applied to detect other targets in this field
Influence of amine group on the adsorptive removal of basic dyes from water using two nanoporous isoreticular Zn(II)-based metal organic frameworks
Abstract
Influence of amine group on the adsorptive removal of basic dyes from water using two nanoporous isoreticular Zn(II)-based metal organic frameworks
Dyes are the most abundant hazardous components existing in the environment because of their extensive use in industries. So, in the present study, two isoreticular Zn(II)-MOFs, TMU-16 and TMU-16-NH2, were used for the adsorptive removal of harmful cationic dyes from aquatic medium. In order to improve the removal efficiency, optimization of the experimental conditions was carried out as a function of pH, MOF dosage, dye concentration and contact time. The maximum removal capacity was obtained at pH 12, 10 mg of MOF and 20 min as the contact time. The adsorption isotherms of each dye over both sorbents matched with the Langmuir model, and the adsorption kinetics followed the pseudo-second order kinetic model. The dye adsorption over TMU-16-NH2 is higher than that over TMU-16, indicating that the addition of amine groups in MOF network played an important role in the adsorption process, because of electrostatic interactions and hydrogen bonding. Thermodynamic studies indicated that adsorption process is spontaneous and endothermic.
Ultra-sensitive aptasensor based on a GQD nanocomposite for detection of hepatitis C virus core antigen
Abstract
Ultra-sensitive aptasensor based on a GQD nanocomposite for detection of hepatitis C virus core antigen
In the present study, by using the aptamer proximity binding assay strategy, a novel electrochemical aptasensor is described for ultrasensitive detection of hepatitis C virus (HCV) core antigen. The immobilization surface is prepared by the modification of a glassy carbon electrode (GCE) with a graphene quantum dots (GQD). GQD were introduced as a novel and suitable substrate for aptamers through p-p stacking interactions, the richness of hydrophilic edges as well as hydrophobic plane in GQD which enhances the aptamer absorption on the electrode surface. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were performed at each stage of the chemical modification process to confirm the resulting surface changes. EIS technique was used as an efficient alternative detection system for HCV core antigen measurement with detection limit 3.3 pg mL1 and two linear concentration range 10e70 pg mL1 and 70e400 pg mL1. Moreover, the fabricated aptasensor could accurately detect HCV core antigen concentration in human serum samples. Such an aptasensor opens a rapid, selective and sensitive route for HCV core antigen detection and provides a promising strategy for potential applications in clinical diagnostics.
Preparation of Modified Magnetic Cobalt Nanoparticles as a New Magnetic Sorbent for the Preconcentration and Determination of Trace Amounts of Lead Ions in Environmental Water and Soil (Air-Dust) Samples
Abstract
Preparation of Modified Magnetic Cobalt Nanoparticles as a New Magnetic Sorbent for the Preconcentration and Determination of Trace Amounts of Lead Ions in Environmental Water and Soil (Air-Dust) Samples
In this study, cobalt magnetic nanoparticles (MNPs) were synthesized and then modified by sodium dodecyl sulfate (SDS) and 2-(5-bromo-2- pyridylazo)-5-diethyl aminophenol ligand (5-Br-PADAP), through a chemical precipitation method. Characterization of the prepared MNP adsorbents was performed by Fourier transform infrared and transmission electron microscopy. Cobalt nanoparticles (NPs) surface modified with SDS and 5-Br-PADAP was evaluated as a nanoparticulate solid-phase extraction (SPE) absorbent for lead ions Pb(II) from water and standard samples, prior to its flame atomic absorption spectrometry determination. Effects of pH, amount of sorbent, desorption solvent, adsorption time, desorption time, and interfering ion concentration on extraction efficiency were investigated. Under optimal conditions, the calibration curve was linear in the range of 1.0–500 ng mL−1of Pb(II) with R2 = 0.998. Detection limit was 1.6 ng mL−1 in the original solution (3Sb/m), and the relative standard deviation for replicate determination of 0.5 μg mL−1 Pb (II) was ±2.7%.
A novel electrochemical aptasensor for highly sensitive and quantitative detection of the streptomycin antibiotic
Abstract
A novel electrochemical aptasensor for highly sensitive and quantitative detection of the streptomycin antibiotic
In the present study,we report a facile approach to employ gold nanoparticle (AuNPs) and thiol graphene quantum dots (GQD-SH) as the nanomaterial for ultrasensitive detection of streptomycin (STR). Based on this strategy, a GQD-SH was immobilized onto the surface of a glassy carbon electrode (GCE). AuNPs have been immobilized on SH groups of GQDs through bonding formation of Au\\S and Apt have been loaded on the electrode surface through the interaction between thiol group of aptamer. By incubating STR as a target onto the surface of the prepared Apt/AuNPs/GQD-SH/GCE as a proposed nanoaptasensor, the Apt/STR complex was formed and the changes of the electrochemical signal were evaluated with the EIS technique. The proposed nanoaptasensor showed wide linear range from 0.1 to 700 pg ml−1. Finally, the proposed nanoaptasensor was successfully applied for the determination of STR in real samples and satisfactory results were obtained.
Determination of Trace Amounts of Cadmium Ions in Water and Plant Samples Using Ligand- Less Solid Phase Extraction-Based Modified Co3O4 Nanoparticles
Abstract
Determination of Trace Amounts of Cadmium Ions in Water and Plant Samples Using Ligand- Less Solid Phase Extraction-Based Modified Co3O4 Nanoparticles
In this study, a new Co3O4 nanoparticles (NPs) coated with sodium dodecyl sulphate (SDS) is developed for preconcentration of trace amounts of cadmium ions (Cd 2+) as a prior step to its determination by flame atomic absorption spectrometry (FAAS). The effects of various parameters, including pH of sample solution, amount of sorbent, flow rates of solution and eluent, sample volume, type, and least amount of the eluent for elution of the Cd 2+ from Co3O4 NPs were studied and optimized. Experimental conditions for effective separation of trace levels of the Cd 2+were optimized with respect to different experimental parameters in Column method. Under the best experimental conditions, the calibration curve was linear in the range of 1.0–500.0 ng.mL−1 of cadmium (Cd) with R2 = 0.999. The detection limit was 0.4ng.mL−1 in the original solution (3Sb/m) and the relative standard deviation for eight replicate determination of 0.1μg.mL−1 Cd was ±2.1%. The method was validated by the analysis of a certified reference material with the results being in agreement with those quoted by manufactures. The developed method was successfully applied to the extraction and determination of Cd in water and food samples with satisfactory results.
A nanohybrid probe based on double recognition of an aptamer MIPgrafted onto a MWCNTs-Chit nanocomposite for sensing hepatitis Cvirus core antigen
Abstract
A nanohybrid probe based on double recognition of an aptamer MIPgrafted onto a MWCNTs-Chit nanocomposite for sensing hepatitis Cvirus core antigen
In this research work, multi-walled carbon nanotubes-chitosan nanocomposite (MWCNTs-Chit) is uti-lized as a special immobilization interface to improve the conductivity and performance characteristicsof the sensors to increase the loading amount of aptamer (Apt) sequence. A novel sensor for the firsttime was constructed for hepatitis C virus (HCV) core antigen (Anti) through combining the benefitsaptasensing and molecular imprinting (MIP) approaches based on electropolymerization of dopamine(DA) around the Apt [HCV core antigen] complex on MWCNTs-Chit modified GCE. The sensor also can bea useful tool for detection of HCV core antigen with low response time, low cost, good sensitivity, and highstability. The analytical performance and application feasibility of the sensor was measured by severaldifferent electrochemical techniques such as cyclic voltammetric (CV), differential pulse voltammetric(DPV), electrochemical impedance spectroscopy (EIS). The sensor response indicates a linear range from5.0 fg/mL to 1.0 pg/mL with a detection limit of 1.67 fg/mL. Moreover, the application of the proposedmethod to determination of HCV core antigen in human serum sample has been successfully evaluated;satisfactory results were obtained, the results show great potential of the fabricated sensor for real sampleanalysis.
Synthesis, characterization and spectroscopic studies of nickel (II) complexes with some tridentate ONN donor Schiff bases and their electrocatalytic application for oxidation of methanol
Abstract
Synthesis, characterization and spectroscopic studies of nickel (II) complexes with some tridentate ONN donor Schiff bases and their electrocatalytic application for oxidation of methanol
Some tridentate Schiff base ligands (L1–L5) and their nickel complexes [NiL (PR3)]; (where L1 = N-salicyliden- 2,3-diamino-cis-2-butenedinitrile, L2 = 3-methoxy-N-salicyliden-2,3-diamino-cis-2-butenedinitrile, L3 = 5- Bromo-N-salicyliden-2,3-diamino-cis-2-butenedinitrile, L4 = 5-nitro - N-salicyliden-2,3-diamino-cis-2- butenedinitrile, L5=5-methoxy-N-salicyliden-2,3-diamino-cis-2-butenedinitrile)were synthesized and characterized by different spectroscopic techniques. The geometry of [NiL2 (PPh3)] and [NiL5 (PPh3)] were determined by X-ray crystallography. Both of the structures show distorted square planer geometry. In addition, the optimized geometries of the ligands and complexes along with their IR spectra were calculated by the density functional theory (DFT). The time-dependent-density functional theory (TD-DFT) was employed to calculate the absorption spectra of the structures. The calculated IR and absorption spectra were compared with the corresponding experimental spectra to confirm the experimental results. The calculated IR and absorption spectra were assigned based on the theoretical calculations. Also, the nickel complexeswere electrochemically dispersed onto multi-wall carbon nanotubes (MWCNTs) and their electrocatalytic activity for the oxidation of methanol have been studied by cyclic voltammetry. Based on the results, the nickel complexeswere found to be active catalysts in the electro-oxidation of methanol.
Encapsulated phosphomolybdic acid in TMU-16 metal organic framework: Study the catalytic activity and structural stability dependent on synthetic solvent
Abstract
Encapsulated phosphomolybdic acid in TMU-16 metal organic framework: Study the catalytic activity and structural stability dependent on synthetic solvent
Encapsulated phosphomolybdic acid in the TMU-16,HPMA@TMU-16, at three different solventswas synthesized and characterized. For characterization studies XRD, ICP, TGA, CHNS, BET, SEM-EDS and TEMmethodswere used. Evidences such as loss of specific surface area, EDS elemental mapping and similar XRD patterns confirmed that HPMA to be import in the TMU-16 pores. A catalytic activity of samples was performed in the oxidation of sulfides and optimum conditions were studied in the dibenzyle sulfide oxidation reactions. Obtained results including short reaction times, selectivity to sulfoxide and reusability exhibited high performance of HPMA@TMU-16 as heterogeneous catalyst. Increasing number of recovered cycles with shorter reaction times revealed effect of polarity of synthetic solvent on the catalytic activity and structural stability.
Preparation an electrochemical sensor for detection of manganese (II) ions using glassy carbon electrode modified with multi walled carbon nanotubechitosan- ionic liquid nanocomposite decorated with ion imprinted polymer
Abstract
Preparation an electrochemical sensor for detection of manganese (II) ions using glassy carbon electrode modified with multi walled carbon nanotubechitosan- ionic liquid nanocomposite decorated with ion imprinted polymer
An electrochemical sensor for the determination of manganese (II) ion with high selectivity was developed by using modified glassy carbon electrode with a nanocomposite film containing immobilized Mn(II)-IIP particles abbreviated as Mn(II)-IIP/MWCNT/Chit/IL/GCE. The manipulation of IIP increases the selectivity of the sensor and the presence of MWCNT/Chit/IL provides significant enhancement of the electron transfer rate during redox reactions. The Mn(II)IIP-NPs were obtained by thermal polymerization of Methacrylic acid (the monomer), ethylene glycol dimethacrylate (cross-linker), 2,2′-azobisisobutyronitrile (chemical initiator), 1-(2-Pyridylazo)- 2-naphthol (manganese-binding ligand), and manganese ions (template ion) in ethanol. The response of the constructed sensor was linear in the range of 2.0 to 9.0 μM with a detection limit of 0.15 μM and much higher sensitivity (130.5 nA μM−1 cm−2). The important parameters such as IIP amount, preconcentration potential and accumulation time were optimized to be 1.0 mg, −1.4 V and 120 s, respectively. The interference of different ionic species with the response of the sensor was also studied. The proposed sensor provides the important advantages of relative high sensitivity, excellent selectivity and operation convenience as well as low detection limit.
A glassy carbon immunoelectrode modified with vanadium oxide nanobelts for ultrasensitive voltammetric determination of the core antigen of hepatitis C virus
Abstract
A glassy carbon immunoelectrode modified with vanadium oxide nanobelts for ultrasensitive voltammetric determination of the core antigen of hepatitis C virus
The authors describe a voltammetric immunoassay for the hepatitis C virus core antigen. It is based on the use of vanadium oxide nanobelts that were used to modify a glassy carbon electrode (GCE). The nanobelts have a large specific surface area that can be heavily loaded with antibody against the hepatitis C virus core antigen. Following blocking with BSA and by using riboflavin as an electrochemical probe, the immuno GCE (best operated at a working voltage of −0.45 V vs. Ag/AgCl) has a linear response that covers the 10 fg·mL−1 to 100 ng·mL−1 core antigen concentration range and a limit of detection as low as 1.3 fg mL−1. Compared to the other redox probes, riboflavin is superior because it is oxidized in the negative potential range, where the number of interfering species for riboflavin is small. The method was successfully applied to the determination of hepatitis C virus core antigen in spiked serum. In our perception, the use of a V2O5 nanobelt film as a support for bioreceptors has a wide scope in that in that it may be extended to immunoassays for various other diagnostically significant analytes.
On-line flow injection solid phase extraction using imprinted polymeric nanobeads for the preconcentration and determination of mercury ions
Abstract
On-line flow injection solid phase extraction using imprinted polymeric nanobeads for the preconcentration and determination of mercury ions
This work reports a new analytical method for the preconcentration and determination of Hg2+ ions based on flow injection technique coupled with a solid phase extraction process. Hg2+ ion imprinted polymeric (IIP) nanomaterials were prepared by using the bulk polymerization procedure, and then applied as an efficient solid phase extractor for selective separation of Hg2+ ions. The prepared sorbent was characterized using FT-IR spectroscopy, scanning electron microscopy (SEM), various thermal analysis methods, and Brunauer, Emmett, and Teller adsorption isotherm analysis (BET). According to the results, surface area, pore volume and average pore diameter of the prepared Hg-IIP were found to be 3.05 102 m2 g1, 1.07 cm3 g1 and 15.33 nm, respectively. In the sorption studies, after preconcentration and loading of Hg2+ ions on the IIP sorbent, its mercury content was eluted by suitable solution and then determined photometrically, by a designed on-line recording process coupled with a flow injection procedure. The influence of the mercury concentration, preconcentration and elution times, nature, volume, and concentration of the eluent, pH, and flow rate of the solution and eluent on the polymer affinity has been investigated. Bound Hg2+ ions can be eluted with 5 mL of nitric acid 1.0 mol L1 and then treated with diphenylthiocarbazone, finally quantified photometrically at 485 nm. The relative standard deviation and detection limit (3r) of the method for eight replicates at optimum pH, were evaluated as 4.2% and 0.036 ng mL1, respectively. The IIP sorbent show an excellent selectivity for Hg2+ ion over other metal ions and was successfully applied to the selective extraction and determination of Hg2+ ion in water and human hair samples.
Impedimetric detection of trinitrotoluene by using a glassy carbon electrode modified with a gold nanoparticle@fullerene composite and an aptamer-imprinted polydopamine
Abstract
Impedimetric detection of trinitrotoluene by using a glassy carbon electrode modified with a gold nanoparticle@fullerene composite and an aptamer-imprinted polydopamine
This study introduces a method based on a combination of aptasensing and molecular imprinting for highly sensitive detection of 2,4,6-trinitrotoluene (TNT). An amino-aptamer with inherent affinity for TNT was mixed with TNT prior to covalent attachement onto a glassy carbon electrode surface which was modified with a nanocomposite of the type gold nanoparticle@fullerene (AuNP@C60). Electropolymerization of dopamine around the aptamer/TNT complex entraps the complex and retains the aptamer. After removal of TNT, it is assumed that the MIP cavity acts synergistically with the embedded aptamer to form a nanohybrid receptor (aptamer-molecular imprinting polymer). This results in recognition properties superior to that of aptamer alone. Benefiting from the double specific molecular recognition property of molecular imprinting polymers and aptamers along with the in situ generation of AuNP onto the surface of the modified GCE leads to superb sensing properties. Properties such as lower limit of detection (3.5 attomolar) and wider linear concentration range of TNT (0.01 femtomolar to 1.5 μmol L−1) are distinctly better than other reported methods. In our perception, this strategy may be extended to various diagnostically relevent proteins using not only aptamers but also other affinity molecules such as affimers, antibody and peptide fragments.
Fabrication of an Electrochemical Immunosensor for Determination of Human Chorionic Gonadotropin Based on PtNPs/Cysteamine/AgNPs as an Efficient Interface
Abstract
Fabrication of an Electrochemical Immunosensor for Determination of Human Chorionic Gonadotropin Based on PtNPs/Cysteamine/AgNPs as an Efficient Interface
An ultrasensitive electrochemical immunosensor for the detection of tumor marker human chorionic gonadotropin (hCG) was developed with a limit of detection as low as 2 pg ml-1 in phosphate buffer. The platinum nanoparticles (PtNPs) were electrodeposited to modify the gold surface and to increase enlarging the electrochemically active sites, resulting in the facilitation of electron exchange. Cysteamine (Cys) self-assembled monolayer was chemisorbed spontaneously on Pt substrates via the Pt-S bond and the amine groups array exposed on the electrode surface was used to anchor AgNPs through electrostatic interaction. AgNPs increased the immobilized amount of antibodies on the electrode to enhance the sensitivity of the sensor. Under optimal experimental parameters, differential pulse voltammetry (DPV) signal changes of the [Fe(CN)6]3-/4- are used to detect hCG with two broad linear ranges: 0.007-1.11 and 1.11-68 ng ml-1. The reported strategy has provided a promising platform for highly sensitive and selective detection of hCG. Finally, the proposed immunosensor is successfully used in detecting hCG in human serum samples.
Using Au@nano-C60 nanocomposite as an enhanced sensing platform in modeling a TNT aptasensor
Abstract
Using Au@nano-C60 nanocomposite as an enhanced sensing platform in modeling a TNT aptasensor
Based on the unique characteristics of the combination of fullerene and gold nanoparticles, we successfully designed a new and facile nanocomposite (Au@nano-C60) to fabricate an aptasensor for the ultra-sensitive and selective detection of TNT. The gold nanoparticles decorated fullerene onto a glassy carbon electrode was prepared using an electrochemical method by the in situ generation of Au nanoparticles onto the surface of the glassy carbon electrode modified with activated fullerene. Successively, the NH2-Apt as a receptor molecule of 2,4,6-Trinitrotoluen was covalently attached onto the modified electrode surface with the resultant nanocomposite. With the addition of the target onto the aptasensor surface and the formation of target/Apt complex, a linear response was obtained from 0.50 fM to 5 mM as well as a limit of detection down to 0.17 fM. The proposed aptasensor shows a wider linear response range and lower limit of detection for the specific detection of 2,4,6-Trinitrotoluen. This newly developed strategy will pave the way to partly meet the requirements in the field of homeland security and public safety.