Growth and Application of Paired Gold Electrode Junctions: Evidence for Nitrosonium Phosphate During Nitric Oxide Oxidation

Interfacial electron-shuttling processes across KolliphorEL monolayer grafted electrodes

Covalently grafted KolliphorEL (a poly(ethylene glycol)-based transporter molecule for hydrophobic water-insoluble drugs; MW, ca. 2486; diameter, ca. 3 nm) at the surface of a glassy-carbon electrode strongly affects the rate of electron transfer for aqueous redox systems such as Fe(CN)6(3-/4-). XPS data confirm monolayer grafting after electrochemical anodization in pure KolliphorEL. On the basis of voltammetry and impedance measurements, the charge transfer process for the Fe(CN)6(3-/4-) probe molecule is completely blocked after KolliphorEL grafting and in the absence of a "guest". However, in the presence of low concentrations of suitable ferrocene derivatives as guests, mediated electron transfer across the monolayer via a shuttle mechanism is observed. The resulting amplification of the ferrocene electroanalytical signal is investigated systematically and compared for five ferrocene derivatives. The low-concentration electron shuttle efficiency decreases in the following sequence: (dimethylaminomethyl)ferrocene > n-butyl ferrocene > ferrocene dimethanol > ferroceneacetonitrile > ferroceneacetic acid.

Amplified electron transfer at poly-ethylene-glycol (PEG) grafted electrodes

Electron transfer at pegylated electrode surfaces is suppressed for Fe(CN)₆^3−/4− and then recovered in the presence of ferrocene-dimethanol.

A dual-electrode flow sensor fabricated using track-etched microporous membranes

A new dual-electrode flow sensor has been fabricated by piling the microporous membrane electrodes which have 7-10μm thickness. The electrode was prepared by sputtering of platinum onto both sides of the membrane filter which contain a smooth flat surface as well as cylindrical pores with uniform diameters. The electrolysis is performed when the sample solution flows through the membrane electrode, and a generated analyte on the first working electrode is instantaneously transported to the surface of second working electrode which is located at the downstream of the first one. In this case, the sample solution surely flows through the pores of the membrane filters. As the result, highly efficient electrolysis was achieved at each electrode, and the collection efficiency values as high as 100% were obtained in the wide range of flow rate. Good responses to the injections of sample solutions were also confirmed in the FIA system.

Generator-collector experiments at a single electrode: exploring the general applicability of this approach by comparing the performance of surface immobilized versus solution phase sensing molecules

We demonstrate proof-of-concept that generator-collector experiments can be performed at a single macroelectrode and used to determine mechanistic information. The practical advantages of such a system over conventional generator-collector techniques are also outlined. The single-electrode generator-collector technique is applied to study the known mechanism of oxygen reduction in aqueous conditions as a model system. We seek to demonstrate that the single-electrode generator-collector approach is capable of detecting local pH changes, immediately adjacent to the electrode surface during a redox reaction. Experiments are performed using a molecular pH probe attached to the electrode surface. Comparison of experimental data with numerical simulations verifies that the reduction of oxygen at pH 6.8 proceeds via a two-electron, two-proton mechanism. Experiments were also performed with a molecular pH probe dissolved in the electrolyte solution in order to explore the feasibility of this approach, which is potentially applicable to a much wider range of electrochemical systems.