Showing papers on "Amperometry published in 2010"

Imaging Local Electrochemical Current via Surface Plasmon Resonance

Abstract: We demonstrated an electrochemical microscopy technique based on the detection of variations in local electrochemical current from optical signals arising from surface plasmon resonance. It enables local electrochemical measurements (such as voltammetry and amperometry) with high spatial resolution and sensitivity, because the signal varies with current density rather than current. The imaging technique is noninvasive, scanning-free, and fast, and it constitutes a powerful tool for studying heterogeneous surface reactions and for analyzing trace chemicals.

Electrochemical determination of nitrite at a bare glassy carbon electrode; why chemically modify electrodes?

Abstract: The oxidation of nitrite was studied at a bare glassy carbon (GC) electrode in aqueous solution using cyclic voltammetry, square wave voltammetry and chronoamperometry. A mechanism for the electrode reaction is proposed. A limit of detection (LOD) of 4 × 1 0 − 7 M was obtained for amperometry and this is evaluated with reference to literature reports for NO 2 − detection; in particular, the possible merits of using chemically modified electrodes as compared to ‘bare’ unmodified electrodes are critically assessed.

A highly sensitive nonenzymatic glucose sensor based on NiO-modified multi-walled carbon nanotubes

Abstract: A highly sensitive and selective glucose biosensor has been constructed by using highly dispersed NiO nanoparticles supported on well-aligned MWCNTs (NiO/MWCNTs) as sensing interface The NiO/MWCNTs nanocomposite was synthesized by magnetron sputtering deposition of NiO nanoparticles on vertically aligned carbon nanotubes The nanocomposite electrode showed high electrochemical activity towards the oxidation of glucose in 020 M NaOH solution At an applied potential of +050 V, it gives a fast response time (< 5 s) and a linear dependence (R = 0997) on the glucose concentration up to 70 mM with an extraordinarily high sensitivity of 177 mA mM-1 cm-2 and a detection limit of 2 μM The interference by the oxidation of common interfering species such as ascorbic acid, dopamine, uric acid, lactose, and fructose is effectively avoided The electrode was used to analyze glucose concentration in human serum samples It allows highly sensitive, stable, and fast amperometric sensing of glucose, which is promising for the development of nonenzymatic glucose sensors

A novel hydrazine electrochemical sensor based on the high specific surface area graphene

Abstract: An ultrasensitive platform is presented for the determination of hydrazine by combining the high specific surface area and higher electrical conductivity of poly(sodium styrenesulfonate) (PSS) graphene nanocomposite film with amperometric detection The PSS-graphene were synthesized by the Hummers method and used to modify a glassy carbon electrode The material was characterized by scanning electron microscopy and is found to be suitable for sensing hydrazine The overpotential of hydrazine on the modified electrode is 031 V which is lower than in many electrochemical sensors The calibration curve for hydrazine is linear in the range from 30 to 300 µmol L−1, and the detection limit is as low as 1 µmol L−1 This is the first report in which such a high sensitivity and low limit of detection has been achieved It is concluded that PSS graphene represents an efficient electron mediator for sensing hydrazine

(110)-Exposed Gold Nanocoral Electrode as Low Onset Potential Selective Glucose Sensor

Abstract: A straightforward electrochemical deposition process was developed to grow gold nanostructures, including nanocoral, nanothorn, branched belt, and nanoparticle, on carbon electrodes by reducing HAuCl4 under constant potentials in mixtures containing CTAC and/or NaNO3. Among the nanostructures, the quasi-one-dimensional nanocoral electrode showed the highest surface area. Because of this, it provided excellent electrochemical performances in cyclic voltammetric (CV) studies for kinetic-controlled enzyme-free glucose oxidation reactions. In amperometric studies carried out at 0.200 V in PBS (pH 7.40, 0.100 M), the nanocoral electrode showed the highest anodic current response. It also offered the greatest sensitivity, 22.6 μAmM−1cm−2, an extended linear range, 5.00 × 10−2 mM to 3.00 × 101 mM, and a low detection limit, 1.00 × 101 μm among the electrodes investigated in this study. In addition, the glucose oxidation by the nanocoral electrode started at −0.280 V, more negative than the one of using a commerc...

Enzyme-free amperometric sensing of glucose using Cu-CuO nanowire composites

Abstract: A non-enzymatic amperometric glucose is reported that is based on an glassy carbon electrode modified with a Cu-CuO nanowire (NW) composite. The morphology and the composition of the nanowire were characterized by scanning electron microscopy and X-ray diffraction, respectively. The modified electrode efficiently catalyzes the oxidation of glucose at less-positive potential (0.30 V) in 0.10 M NaOH solution in the absence of any enzymes or redox mediators. The sensor was successfully used for the amperometric sensing of glucose. Linear response was obtained over the concentration range from 0.1 to 12 mM. The common interfering agents ascorbic acid and uric acid do not interfere with the determination of glucose. The modified electrode features high sensitivity, low working potential, excellent stability, and fast amperometric sensing of glucose. Thus it is promising for the future development of non-enzymatic glucose sensors.

Highly Sensitive Amperometric Cholesterol Biosensor Based on Pt-Incorporated Fullerene-like ZnO Nanospheres

Abstract: A highly sensitive amperometric biosensor based on Pt-incorporated fullerene-like ZnO hybrid nanospheres has been investigated. Pt−ZnO nanospheres (PtZONS) with diameters in the range 50−200 nm have been successfully synthesized by electrodeposition on a glassy carbon electrode (GCE). The Pt nanoparticles in ZnO nanospheres have been identified with high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS). The doped Pt nanoparticles demonstrate the abilities to electrocatalyze the oxidation of hydrogen peroxide and substantially raise the response current. The sensitivity of the PtZONS/GCE to hydrogen peroxide is 147.8 μA μM−1 cm−2, which is much higher than that of a conventional electrode. The PtZONS/GCE was functionalized with cholesterol oxidase (ChOx) by physical adsorption. The enzyme electrode exhibits a very high and reproducible sensitivity of 1886.4 mA M−1 cm−2 to cholesterol with a response time less than 5 s and a linear range from 0.5 to 15 μM. F...

Glucose biosensor from covalent immobilization of chitosan-coupled carbon nanotubes on polyaniline-modified gold electrode.

Abstract: An amperometric glucose biosensor was prepared using polyaniline (PANI) and chitosan-coupled carbon nanotubes (CS-CNTs) as the signal amplifiers and glucose oxidase (GOD) as the glucose detector on a gold electrode (the Au-g-PANI-c-(CS-CNTs)-GOD biosensor). The PANI layer was prepared via oxidative graft polymerization of aniline from the gold electrode surface premodified by self-assembled monolayer of 4-aminothiophenol. CS-CNTs were covalently coupled to the PANI-modified gold substrate using glutaradehyde as a bifunctional linker. GOD was then covalently bonded to the pendant hydroxyl groups of chitosan using 1,4-carbonyldiimidazole as the bifunctional linker. The surface functionalization processes were ascertained by X-ray photoelectron spectroscopy (XPS) analyses. The field emission scanning electron microscopy (FESEM) images of the Au-g-PANI-c-(CS-CNTs) electrode revealed the formation of a three-dimensional surface network structure. The electrode could thus provide a more spatially biocompatible microenvironment to enhance the amount and biocatalytic activity of the immobilized enzyme and to better mediate the electron transfer. The resulting Au-g-PANI-c-(CS-CNTs)-GOD biosensor exhibited a linear response to glucose in the concentration range of 1-20 mM, good sensitivity (21 μA/(mM·cm(2))), good reproducibility, and retention of >80% of the initial response current after 2 months of storage.

Electrochemical behavior and application of Prussian blue nanoparticle modified graphite electrode

Abstract: Prussian blue nanoparticles (PBNPs) were immobilized on the surface of a graphite electrode (GE) through a simple adsorption route and then the modified surface was covered with a layer of Nafion. The electrochemical behavior of the resulting sensor was investigated using cyclic voltammetry and chronoamperometry. The sensor showed good electrocatalytic activity toward hydrogen peroxide reduction, and it was successfully used for the amperometric detection of H2O2. The calibration curve for hydrogen peroxide determination was linear over 2.1 x 10(-6) to 1.4 x 10(-4) M mol L-1 with a detection limit (S/N = 3) of 1.0 x 10(-6) mol L-1. Additionally, further modification of the proposed sensor with glucose oxidase led to the fabrication of a glucose biosensor that showed a good performance for determination of glucose. (c) 2010 Elsevier B.V. All rights reserved. (Less)

Electrochemical Oxidation and Sensitive Determination of Acetaminophen in Pharmaceuticals at Poly(3,4‐ethylenedioxythiophene)‐Modified Screen‐Printed Electrodes

Abstract: The current study reports electrocatalytic oxidation of acetaminophen at screen-printed electrode (SPE) modified with electrogenerated poly(3,4-ethylenedioxythiophene) (PEDOT) film. Cyclic voltammetric studies show that the SPE/PEDOT electrode lowers overpotentials and improves electrochemical behavior of acetaminophen (ACAP) in aqueous buffer solutions, compared to the bare SPE. Excellent analytical features are achieved, including high sensitivity, low detection limit and satisfactory dynamic range, by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and flow-injection amperometry (FIA) under optimized conditions. The proposed methods obtain satisfactory results in detection of acetaminophen in two commercial tablets.