Xingyao Zhou

The influence of surfactants on the electron-transfer reaction at self-assembled thiol monolayers modifying a gold electrode

Monolayer films of thiols with different terminal groups (CH3, COOH and NH2) were prepared on gold electrodes using a self-assembling procedure. Cyclic voltammetry was used to investigate the electron-transfer reaction of potassium ferricyanide at the thiol modified gold electrode in the presence of surfactants. It was found that surfactants show some effects on the electron-transfer reaction at the thiol modified electrode. Cationic surfactants can improve the reversibility of a redox reaction at the thiol modified gold electrodes, while anionic surfactants cause a little inhibition of electron transfer of the redox at both methyl and carboxyl terminal thiol modified gold electrodes. Surfactants can interact with thiol monolayers in different ways, changing the structure and properties of the monolayer film, and can further affect electron transfer at the modified gold electrode.

Determination of Hydrogen Peroxide in Rainwater by Using a Polyaniline Film and Platinum Particles Co-Modified Carbon Fiber Microelectrode

Four types of carbon fiber microelctrodes modified with polyaniline (PAn) and platinum particles (Pt) were fabricated to determine H2O2 at + 0.60 V (vs. SCE). The sensitivity, stability and selectivity of different electrodes were compared. The electrode modified with a sandwich film of PAn-Pt-PAn offered the best result. The linear range was 4.0 × 10−7–2.4 × 10−4 M with a detection limit of 1.0 × 10−7 M. The relative standard deviation (RSD) for 10 μM H2O2 was 1.9 % (n =7). The electrode was used to determine the H2O2 in the rainwater.

The Electrochemical Characteristics of C60-Glutathione Modified Au Electrode and the Electrocatalytic Oxidationof NADH

C60 was covalently attached onto a self-assembly monolayer (SAM) of glutathione (GSH) formed on a Au electrode. Characterization of the resulting monolayer was carried out on a FT-IR spectrometer and its electrochemical properties were investigated with cyclic voltammetry and impedance methods. It was found that the pinholes on the C60-GSH monolayer showed the response of the opening and closing with the change of pH. The modified electrode can be used to determine NADH in neutral solution.

Application of a platinum dual-disk microelectrode to measurement of the electron transfer number of dioxygen reduction

Abstract Dual-disk microelectrodes with interelectrode gap widths of 5 to 48 μm were used for the measurement of the electron transfer number n app of dioxygen reduction. The effects of the gap width, the scan rate and the diffusion coefficient on the generation-collection properties were studied. An equation for n app was derived and a semi-empirical expression of the collection efficiency was obtained. On the bare platinum electrode, the reduction of dioxygen is dominated by a four-electron reaction. On the polypyrrole (ppy) film containing nanodispersed platinum particles, more H 2 O 2 is produced and its catalytic activity varies with the conductivity of the film. The n app is affected by the pH value. The diffusion coefficient of H 2 O 2 in 1.0 M KOH determined by the dual-disk microelectrode is 1.29 × 10 −5 cm 2 s −1 .

In situ study of the conductivity of the electrochemically deposited polyaniline film using a dual-disk microelectrode

A conductivity equation based on the dual-disk microelectrode was derived. This electrode was used for in situ measurement of the conductivity of polyaniline. Some factors such as electrochemical potential, solution pH, scan rate and over-oxidation, which influence the conductivity of polyaniline, were conveniently controlled by this electrode. Experimental results proved that this electrode is very useful for measuring the relative conductivity in situ and studying the conducting mechanism of conductive polymers.

Electrochemical Study of a Polypyrrole Film/Decanethiol Self‐Assembled Monolayer on a Gold Electrode

Cyclic voltammetry and chronoamperometry were used to study the deposition of polypyrrole on a decanethiol self-assembled monolayer modified gold electrode (PPY/SAM/Au). The voltammetric behavior of the PPY/SAM film was investigated in the presence of several different electrolytes. It is found that the SAM shows great influence on the nucleation and growth of the PPY film. The reaction of the SAM and the anions causes the different voltammetric behavior of the polymerization of pyrrole on the modified electrode. Chronoamperometry shows the nucleation and growth of the PPY is initially inhibited but followed by a rapid increase. The SAM also influences electrochemical behavior of PPY film. Experiments show that the SAM can greatly depress the diffusion of anions in the PPY film, and minimize the background capacitance current.

Voltammetric Study of a Cupric Hexacyanoferrate Monolayer Immobilized on Mixed Dodecanethiol-Glutathione Self-Assembled Monolayer Modified Gold Electrode

Mixed dodecanethiol-glutathinone self-assembled monolayers (DDT-GSH) were prepared on a gold electrode and further derivatized to form a monolayer of cupric hexacyanoferrate (CuHCF). Electrochemical behavior of the modified electrode was investigated by cyclic voltammetry. This inorganic monolayer modified electrode is electroactive and its surface concentration is 4.2×10–10 mol cm–2. It is observed that this modified electrode shows selectivity to potassium ion and exhibits an ideal Nernstian response with a slope of 60 mV/decade to potassium ions in the range from 10–2 to 1.0 mol L–1.

In situ study of the resistance of the electropolymerized polypyrrole film using platinum dual-disk microelectrodes

The resistance of the polypyrrole film (PPy) was measured in situ by the dual-disk microelectrode. Some factors (such as the kinds of electrolyte, anionic concentration, oxidation potential and solution pH) which influence the resistance or the stability of the film have been studied in detail. The oxidation potential had the most critical effect on the resistance and the stability of the film.

Development of Disposable Electrochemical Sensor With ReplaceableGlucose Oxidase Tip

A new type of disposable electrochemical sensor, which consists of a piece of Nafion membrane and a microdisk electrode, is developed. The Nafion membrane, which is butted by the electrode to actualize the electrochemical reaction, acts as the immobilization bed for mediator (anthraquinone) and enzyme (glucose oxidase). The sensor is not vulnerable to being broken or contaminated. By replacing the immobilization beds with different mediators and different enzymes in series, the sensor may be employed for the rapid analysis of a multi-component sample. The sensor exhibits a rapid, stable response to glucose. A consecutive calibration test shows that the original tip has an active period greater than 24 hours and the storage life time longer than 3 weeks. The linear range and the sensitivity of the original sensor are 6 mM and 0.52 nA/mM, respectively.