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An electrochemical sensor based on a copolymer poly(4-vinylpyridine)-co-poly(acrylonitrile), P4VP-co-PAN, and Fe2O3 nanoparticle film modified glassy carbon electrode was developed for the determination of glucose. We studied the response of glucose with the proposed electrode, and determined the optimum conditions by changing the potential, pH and P4VP-co-PAN. The current response measurements were performed in PBS (c=0.1 M) with a potential of 0.7 V. The current response of this glucose sensor showed a linear relationship with the concentration in the range of 2.5 μM-0.58 mM (r=0.997). The experimental results demonstrate that this method has such merits as simple operation, low cost, high sensitivity, long term stability and good reproducibility, with satisfactory results., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Multi-walled carbon nanotubes (MWCNTs)-nanoflake-like SnS(2) nanocomposite were designed for immobilization of glucose oxidase (GOx). The direct electrochemistry of GOx and glucose sensing at MWCNTs-SnS(2) modified glassy carbon electrode were studied. Compared with single MWCNTs or SnS(2), the MWCNTs-SnS(2) film has larger surface area and provides a more favorable microenvironment for facilitating the electron transfer between enzyme and electrode surface. The properties of GOx/MWCNTs-SnS(2) were examined by scanning electron microscopy, UV-vis spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry. The immobilized enzyme on MWCNTs-SnS(2) composite film retained its native structure and bioactivity and showed a surface controlled, reversible two-proton and two-electron transfer reaction with a apparent electron transfer rate constant of 3.96 s(-1). The constructed glucose biosensor exhibits wider linear range from 2.0×10(-5) M to 1.95×10(-3) M, much lower detection limit of 4.0×10(-6) M at signal-to-noise of 3 and higher sensitivity of 21.65 mA M(-1) cm(-2) than our previous nanoflake-like SnS(2)-based glucose sensor. The proposed biosensor has excellent selectivity, good reproducibility, and acceptable operational stability and can be successfully applied in the reagentless glucose sensing at -0.43 V. This MWCNTs-SnS(2) composite provides a new avenue for immobilizing proteins and fabricating excellent biosensors., (Copyright © 2012 Elsevier B.V. All rights reserved.)

An ultrasensitive electrochemical method for simultaneous determination of lead and cadmium was first developed using the novel bismuth-Nafion-medical stone doped disposable electrode (an improved wax-impregnated graphite electrode). Through the synergistic sensitization effect of the resulting composite material, the disposable electrode showed remarkable electrochemical responses to lead and cadmium. The oxidation of the two metals produced two well-defined and separated square wave peaks at about -0.62 V for Pb(2+) and -0.85 V for Cd(2+), respectively. The effects of the amount of medical stone, concentration of Nafion, thickness of bismuth, pH of buffer solution, deposition potential, accumulation time, voltammetric measurement and possible interferences were investigated in detail. Under the optimal conditions, the fabricated electrode exhibited linear ranges from 2.0 to 12.0 μg L(-1) with detection limit of 0.07 μg L(-1) for lead and 2.0-12.0 μg L(-1) with detection limit of 0.47 μg L(-1) for cadmium. The assay results of heavy metals in wastewater with the proposed method were in acceptable agreement with the atomic absorption spectroscopy method., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A novel photoelectrochemical sensor for detection of the organophosphorus pesticide (OP) dichlofenthion using nanometer-sized titania coupled with a screen-printed electrode is presented. Nonelectroactive dichlofenthion can be indirectly determined through the photocatalytical degradation of dichlofenthion with nanometer-sized titania. The electrochemical characterization and anodic stripping voltammetric performance of dichlofenthion were evaluated using cyclic voltammetric (CV) and differential pulse anode stripping voltammetric (DPASV) analysis, respectively. DPASV analysis was used to monitor the amount of dichlofenthion and provide a simple, fast, and facile quantitative method for dichlofenthion. Operational parameters, including the photocatalysis time, pH of buffer solution, deposition potential, and accumulation time have been optimized. The stripping voltammetric response is linear over the 0.02-0.1 and 0.2-1.0 μmol/L ranges with a detection limit of 2.0 nmol/L. The assay result of dichlofenthion in green vegetable with the proposed method was in acceptable agreement with that of the gas chromatograph-mass spectrometer (GC-MS) method. The promising sensor opens a new opportunity for fast, portable, and sensitive analysis of OPs in environmental samples.

We have developed an impedimetric immunosensor for the determination of bovine interleukin-4, a cytokine involved in the immune response to certain parasites and the development of some bovine diseases. Monoclonal antibody against bovine interleukin-4 was immobilized on a glassy carbon electrode modified with reduced graphene oxide and chitosan. Transmission electron microscopy, static contact angle measurement, and electrochemical impedimetry are used to characterize the immunosensor. The nanocomposite possesses a high surface area that is well suited for the immobilization of antibody. The relative increase in impedance on exposure of the sensor to solutions containing bovine interleukin-4 is linearly proportional to its logarithmic concentration in the 0.1 to 50 ng mL and the detection limit is 80 pg mL. The immunosensor is selective, well reproducible, and acceptably stable. It presents a useful tool for further studies on the role of this cytokine in the immunology and pathogenesis of bovine diseases. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In this work, a novel chemically modified electrode is constructed based on metal–organic frameworks and β-cyclodextrin (Cu3(BTC)2/β-CD, BTC = benzene-1,3,5-tricarboxylate) composite material. The electrode was used for simultaneous determination of guanine and adenine in a sequential injection lab-on-valve format and exhibited sensitive responses to guanine and adenine oxidation due to the π–π stacking interaction of Cu3(BTC)2 and the inclusion behavior of β-CD. The analytical performance was assessed with respect to the supporting electrolyte and its pH, accumulation time and accumulation potential, and the fluid flow rates. Under optimal conditions, linear calibration ranges for both guanine and adenine were from 1.0 × 10−7 to 1.0 × 10−5 mol L−1, and detection limits (S/N = 3) were found to be 5.2 × 10−8 and 2.8 × 10−8 mol L−1, respectively. The proposed sensor showed advantages of high sensitivity, simple sample preparation protocol, enhanced throughput and good reproducibility. Finally, the practical application of the proposed sensor has been performed for the determination of guanine and adenine in real samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks have been the subject of intense research because of their unique physicochemical properties. The presented study investigates the application of multi-wall carbon nanotubes and metal–organic frameworks (MWCNTs@Cu3(BTC)2) nanoparticles-modified electrode for the determination of trace levels of lead. The nanocomposites were prepared by solvothermal synthesis and characterized in detail. The experimental procedure was carried out by accumulating lead on the electrode surface and subsequently measuring with differential pulse anodic stripping voltammetry in a lab-on-valve format. The main parameters affecting the analytical performance, including the amount of MWCNTs@Cu3(BTC)2 suspension, supporting electrolyte and its pH, stripping mode, and flow rate, have been investigated in detail. Under the optimum conditions, the oxidation peak current displayed a calibration response for lead over a concentration range from 1.0 × 10−9 to 5.0 × 10−8 mol L−1 with a excellent detection limit of 7.9 × 10−10 mol L−1. The relative standard deviation of 7 successive scans was 3.10% for 1.0 × 10−8 mol L−1 lead. The established method showed a great improvement in sensitivity and sample throughput for lead analysis. [ABSTRACT FROM AUTHOR]

Abstract: A new and simple method for fabricating controllable insulated nanometer-sized platinum electrodes is presented. Electrochemical etching of platinum wire is employed, and then a repeated process of cycle voltammetric deposition of electrophoretic paint and heat curing for shrink film follows which effectively controls the size of the nanoelectrodes, which is different from previous DC electrolysis deposition. This technique allows complete insulation of the whole body of the etched platinum wire, except for the very tip with the shrink film during heat curing of the film, leaving an electrochemical active area with effective diameters of nanometers. The process overcomes the pinhole formation resulting from the electrophoretic paint deposition process. The size of the platinum electrodes and the thickness of the deposed paint for insulation can be properly controlled and reproduced. The fabricated electrodes show ideal steady-state voltammetric behaviors from which the effective areas of the nanoelectrodes are measured. The effective radius of the prepared nanoelectrodes ranges from 3.1nm to hundreds of nanometers. [Copyright &y& Elsevier]

Benorilate was determined by the differential pulse voltammetry (DPV) using a carbon paste electrode in 1.25 x 10-3 mol . l-1 KH2PO4 and Na2HPO4 buffer solution (pH = 6.88, 25°C). The anodic peak potential was +1.020V (versus saturated calomel electrode (SCE)). A good linear relationship was realized between the anodic peak currents and benorilate concentrations in the range of 2.0 x 10-7 to 4.5 x 10-4mol . l-1 with the detection limit of 5.0 x 10-8mol . l-1. The recovery was 94.3 to 104.6% with the relative standard deviation of 3.5% (n = 9). The pharmaceutical preparations, benorilate tablets samples, were determined with desirable results. [ABSTRACT FROM AUTHOR]

Abstract: This study was carried out to develop the application of modified carbon fiber electrode in environmental detection, by which chromium (III) ion in water could be electrochemically detected. The modified carbon fiber electrode manifested a linear response within the range of 1.9×10−6–4.6×10−4 molL−1 (R =0.9939) and the detection limit was 7.9×10−7 molL−1. The effect factors were studied to reveal the optimal conditions in the detection of chromium (III) in water, such as pH of total ionic strength adjustment buffer, the concentration of calix[4]resorcinarene, sweep cycles, and so on. The modified carbon fiber electrode, the diameter of which was about 7μm, was characterized by field emission scanning electron microscopy and electrochemical impedance spectroscopy. Also, the proper mechanism was discussed. The identification of chromium (III) was mainly attributed to the cavity of the calix[4]resorcinarene that the chromium (III) ion could enter into the inner of calix[4]resorcinarene because of the particular structure of calix[4]resorcinarene. [Copyright &y& Elsevier]

Non-invasive wearable sweat glucose sensors are expected to be highly desirable for personalized diabetes management. Therefore, developing facile, convenient, and scalable manufacturing method of such wearable sensors is urgently needed. Herein, we report a simple and low-cost stamping-vacuum filtration dry transfer (SVFDT) method for construction of a wearable sweat glucose electrochemical sensor. In this patch, a three-electrode array template was made by using a polyvinyl chloride (PVC) stamp, followed by the preparation of multiwalled carbon nanotubes (MWCNTs)/polydimethylsiloxane (PDMS) (MP) film electrode using the vacuum-filtration dry transfer method. In addition, for further enhancing the conductivity of the electrode, another similar stamp with a raised surface dipping carbon nanotubes (CNTs) conductive coating was stamped on the surface of the MP electrode to obtain CNTs/MWCNTs/PDMS (CMP) electrode. CMP electrode was modified with the enzyme-like Ni-Co metal-organic framework (MOF) material which showed good electro-catalytic activity and achieved high sensitivity for glucose detection with a low detection limit of 6.78 μM and a wide linear range of 20 μM - 1.1 mM. More importantly, the Ni-Co MOF modified CMP (NCMP) electrode also displayed high stability under stretching and bending conditions. Finally, the sweat absorbent cloth was combined with the NCMP film electrode to form a wearable flexible electrochemical sensor patch, which could adhere to the skin to enrich sweat and realize real-time detection of sweat glucose with high accuracy. This SVFDT method can also be applied to the fabrication of other electronic devices. [Display omitted] • A wearable sweat glucose electrochemical sensor based on bimetallic MOF. • SVFDT method was used for prepare CMP film electrode. • NCMP film based sensor showed high performance for glucose detection. • An NCMP film based on-body sensor for real-time monitoring of sweat glucose. [ABSTRACT FROM AUTHOR]

The accurate measurement of nitrate in PM 2.5 is essential for a complete understanding of the effects of aerosols on human health, the impact of aerosols on the radiative balance of the earth and the role of aerosols in visibility problems. In this paper, we present a novel, quick, easy, cheap and eco-friendly electroanalytical procedure for the determination of nitrate in PM 2.5 samples using a carbon-fiber micro-disk electrode (CFMDE) coupled with square-wave voltammetry (SWV). Under optimal experimental conditions the nitrate SWV response increases linearly with nitrate concentration over a range of 0.003–2.0 mmol L −1 , and the detection limit is 1.10 μmol L −1 ( S / N =3). Nitrate contents in daily PM 2.5 of Yangzhou in China were detected successfully by employing this novel method, and the results were compared well with those obtained by using ion chromatography. Then, we detected nitrate in two-hour PM 2.5 filter samples via the standard addition method, and the concentrations were applied in an analysis of the daily change of nitrate contained in PM 2.5 of Yangzhou. The research in this work indicates that the electrochemical method opens a new opportunity for fast, portable, and sensitive analysis of components in PM 2.5 . [ABSTRACT FROM AUTHOR]

Abstract: An electrochemical sensor based on a self-made electrode from recordable CDs was developed for the non-enzymatic detection of glucose by chronoamperometry. We discussed the amperometric current response of glucose with the change of potential, pH and electrode area, and determined the optimum detection conditions. The current response measurements were performed in a phosphate buffered solution (pH 6.5) with a potential of −0.50V, and presented a linearity over the range of 0.5–13mmol/L (r =0.996). The experimental results of the designed sensor demonstrate that this method has merits such as simple operation, low cost and rapid responses. The results of detecting glucose in blood samples were satisfactory. [Copyright &y& Elsevier]

Abstract: A Fe3O4/multiwall carbon nanotubes/β-cyclodextrin (Fe3O4/MWCNTs/β-CD) modified electrode, for highly sensitive and automated hypoxanthine measurements, was developed in a sequential injection lab-on-valve system. The electrochemical oxidation behavior of hypoxanthine was investigated in phosphate buffer solution by cyclic voltammetry and linear sweep voltammetry. The Fe3O4/MWCNTs/β-CD modified electrode exhibits preferably analytical characteristics in electrocatalytic activity towards the oxidation of hypoxanthine. Under optimized conditions, the log oxidation peak current intensity was proportional to log hypoxanthine concentration covering the range from 5.0×10−8 to 1.0×10−5 molL−1 with a correlation coefficient of 0.9965. A detection limit of 0.3×10–8 molL−1 was achieved along with a sampling frequency of 20h−1. This hyphenated system offers some advantages in terms of rapidness, sensitivity and ease of manipulation. Its further applications were utilized for the determination of hypoxanthine in meat samples. [Copyright &y& Elsevier]

Abstract: In this work, a kojic acid electrochemical sensor, based on a non-covalent molecularly imprinted polymer (MIP) modified electrode, had been fabricated in the lab-on-valve system. The sensitive layer was synthesized by cyclic voltammetry using o-phenylenediamine as the functional monomer and kojic acid as the template. The template molecules were then removed from the modified electrode surface by washing with NaOH solution. Differential pulse voltammetry method using ferricyanide as probe was applied as the analytical technique, after extraction of kojic acid on the electrode. Chemical and flow parameters associated with the extraction process were investigated. The response recorded with the imprinted sensor exhibited a response in a range of 0.01–0.2μmolL−1 with a detection limit of 3nmolL−1. The interference studies showed that the MIP modified electrode had excellent selectivity. Furthermore, the proposed MIP electrode exhibited good sensitivity and low sample/reagent consumption, and the sensor could be applied to the determination kojic acid in cosmetics samples. [Copyright &y& Elsevier]

Abstract: This work exploited a sequential injection lab-on-valve (LOV) system for the determination of cadmium by anodic stripping voltammetry (ASV). A miniaturized electrochemical flow cell (EFC) was fabricated in LOV, in which a nafion coated bismuth film electrode was used as working electrode. The cadmium was electrodeposited on the electrode surface in bismuth solution, and measured with the subsequential stripping scan. Under optimal conditions, the proposed system responded linearly to cadmium concentrations in a range 2.0–100.0μgL−1. The detection limit of this method was found to be 0.88μgL−1. By loading a sample volume of 800μL, a sampling frequency of 22 determinations h−1 was achieved. The repeatability expressed as relative standard derivation (R.S.D.) was 3.65% for 20μgL−1 cadmium (n =11). The established method was applied to analysis of trace cadmium in environmental water samples and the spiked recoveries were satisfactory. [Copyright &y& Elsevier]

Abstract: A novel one-step approach to Pt nanopore electrode ensembles (NEEs) has been developed using an amphiphilic block copolymer [polystyrene-block-poly (acrylic acid)] self-assembly. This procedure is simple and fast, and requires only conventional, inexpensive electrochemical instrumentation. Electrochemical methods are used to characterize the Pt nanopore electrode ensembles prepared using this new procedure. And the capacitance and voltammetric characteristics for the NEEs have been examined. At lower scan rates, it remains the features of a single nanoelectrode, while at high scan rates the nanoelectrodes act independently. This is an important feature for vivo sensing and other electroanalytical applications. [Copyright &y& Elsevier]

Abstract: A new and simple method for fabricating controllable insulted nanometer-sized carbon electrodes is presented. Electrochemical etching of carbon fibers is employed, and then a repeated process of cycle voltammetric deposition of electrophoretic paint and heat cure for film shrink is followed which controls effectively the size of nanoelectrodes. This technique allows complete insulation of the whole body of the carbon fiber etched except for the very tip with the film shrink during heat curing of the film, leaving an electrochemical active area with effective diameters of nanometers. The process overcomes the pinhole formation resulted from the electrophoretic paint deposition process. The fabricated electrodes show ideal steady-state voltammetric behaviors from which the effective areas of nanoelectrodes are measured. The effective radius of the nanoelectrodes prepared ranges from tens of nanometer to hundreds of nanometer. [Copyright &y& Elsevier]

Abstract: Copper nanoparticles, stabilized by cysteine, have been formed thin-films on indium tin oxide (ITO) electrodes with (3-mercaptopropyl) trimethoxysilane (MPTMS). Scanning electron micrograph (SEM) demonstrates that the films are uniform and the copper nanoparticles are homogeneously distributed on the ITO electrode surface. Electrochemical experiments reveal that the obtained copper nanoparticles modified electrodes show improved electron-transfer characteristics and exhibit high electrocatalytic activity to the reduction of nitrite and nitric oxide, which can be utilized as an efficient electrochemical sensor. [Copyright &y& Elsevier]