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Trevor J Davies

Publications and source records attributed to Trevor J Davies.

12 recordsLinked to original sources
PubMed2006

Gold ultra-microelectrode arrays: application to the steady-state voltammetry of hydroxide ion in aqueous solution.

Gold ultra-microelectrode arrays are used to explore the electrochemical oxidation of hydroxide ions and are shown to be analytical useful. Two types of ultra-microelectrode arrays are used; the first consist of 256 individual electrodes of 5 microm in radius, 170 of which are electrochemically active in a cubic arrangement which are separated from their nearest neighbour by a distance of 100 microm. The second array compromises 2597 electrodes of 2.5 microm in radius and of which 1550 of which are electrochemically active in a hexagonal arrangement separated by the nearest neighbour by 55 microm. Well defined voltammetric waves are found with peak currents proportional to the concentration of hydroxide ions in the range 50 microM to 1 mM. Detection limits of 20 microM using the 170 ultra-microelectrode and 10 microM with the 1550 ultra-microelectrode array are shown to be possible but with a higher sensitivity of 4 mA M(-1) observed using the 1550 ultra-microelectrode array compared to 1.2 mA M(-1) with the 170 ultra-microelectrode array.

Journal Article↗
PubMed2005

Regular arrays of microdisc electrodes: simulation quantifies the fraction of 'dead' electrodes.

Arrays of microdisc electrodes have found widespread use in electroanalysis. These are commonly produced lithographically and practical arrays may contain up to hundreds of individual disc electrodes (e.g. of gold, platinum, indium,...) to maximise sensitivity and minimise limits of detection. Typically, however, the lithographic fabrication process is imperfect resulting in a significant fraction (often tens of percent) of electrochemically inactive electrodes. We demonstrate that a 2-dimensional simulation based on the diffusion domain approximation in conjugation with simple experiments on the ferrocyanide redox couple in aqueous solutions can be used to rigorously 'count' the number of active electrodes in a non-destructive fashion. The agreement with an independent count in which active electrodes are identified via electro-plating with copper followed by ex situ microscopic examination is quantitatively excellent.

Calibration↗
PubMed2005

Insights into the role of the liquid-liquid interface in biphasic reactions: the reaction of vitamin B12s(aq) with vicinal dibromides(oil).

Electrocatalytic processes can take place either homogeneously in a single liquid phase or heterogeneously at the liquid-liquid interface formed in emulsions. This Article addresses the question as to whether a change in rate and/or mechanism can occur between the two possibilities. Specifically, cyclic voltammetry and electrosynthetic experiments are used to demonstrate that for the vitamin B12 mediated reduction of vicinal dibromides producing olefins, electric field effects likely operate at the liquid-liquid interface which can change the populations of different conformers relative to the single homogeneous-phase experiment, leading to significant changes in rate.

Electrochemistry↗
PubMed2005

Boron-doped diamond microdisc arrays: electrochemical characterisation and their use as a substrate for the production of microelectrode arrays of diverse metals (Ag, Au, Cu)via electrodeposition.

A novel boron-doped diamond (BDD) microelectrode array is characterised with electrochemical and atomic force microscopic techniques. The array consists of 40 micron-diameter sized BDD discs which are separated by 250 microns from their nearest neighbour in a hexagonal arrangement. The conducting discs can be electroplated to produce arrays of copper, silver or gold for analytical purposes in addition to operating as an array of BDD-microelectrodes. Proof-of-concept is shown for four separate examples; a gold plated array for arsenic detection, a copper plated array for nitrate analysis, a silver plated array for hydrogen peroxide monitoring and last, cathodic stripping voltammetry for lead at the bare BDD-array.

Arsenic↗
PubMed2005

Voltammetric sizing of inert particles.

The average size of inert particles is determined using a simple electrochemical procedure. Alumina particles are deposited on an edge-plane graphite electrode, and a cyclic voltammogram is recorded. The scan rate employed varies between 0.2 and 2 V s(-1). At these scan rates the diffusion layer thickness is greater than the size of the alumina particles, minimizing the influence of the particles' height on the observed voltammetry. The average size of the particles is determined via comparison of the experimental voltammograms with simulations.

Journal Article↗
PubMed2005

Electrochemical cell for surface analysis.

We present a simple cost-effective design for an HOPG electrode that is well suited to voltammetric experiments accompanied by surface analysis. The utility of the electrode is demonstrated by an AFM study on the morphology of electrodeposited MoO2 nanowires. The design can be applied to a wide range of electrode materials.

Journal Article↗
PubMed2004

Electrocatalysis at graphite and carbon nanotube modified electrodes: edge-plane sites and tube ends are the reactive sites.

Carbon, and particularly graphite in its various forms, is an attractive electrode material. Two areas of particular interest are modified carbon electrodes and carbon nanotube electrodes. In this article we focus on the relationship between surface structure and electrochemical and chemical reactivity of electrodes based on these materials. We overview recent work in this area which has led us to believe that much of the catalytic activity, electron transfer and chemical reactivity of graphitic carbon electrodes is at surface defect sites, and in particular edge-plane-like defect sites. We also question the claimed special "catalytic" properties of carbon nanotube modified electrodes.

Catalysis↗
PubMed2004

Investigation of modified basal plane pyrolytic graphite electrodes: definitive evidence for the electrocatalytic properties of the ends of carbon nanotubes.

The basis of the electrocatalytic nature of multi-wall carbon nanotubes is suggested to reside in electron transfer from the ends of nanotubes, which structurally resemble the behaviour of edge plane (as opposed to basal plane) graphite, and is demonstrated via the comparison of the electrochemical oxidation of epinephrine and the electrochemical reduction of ferricyanide at nanotube-modified electrodes using different types of graphite electrodes and with C(60)-modified electrodes.

Journal Article↗
PubMed2004

A self-catalytic carbon paste electrode for the detection of vitamin B12.

A simple, sensitive, and selective method for the detection of vitamin B12 (cyanocobalamin) is presented. A carbon paste electrode has been constructed with trans-1,2-dibromocyclohexane (DBCH) acting as both the paste binder and a reactive material facilitating the electrocatalytic detection of the target. The latter reaction is based on the electroreduction of the Co(III) center in vitamin B12 to Co(I), which specifically reacts with DBCH to produce electrocatalytic currents with the regeneration of Co (II); a detection limit of 8.5 x 10(-10) mol dm(-3) (based on 3sigma) was found. The electrode has been successfully used for the quantification of vitamin B12 in pharmaceutical products and biological matrix media.

Carbon↗
PubMed2002

Photoelectrochemical dechlorination of phenols.

The photoelectrochemical reductions of 4-chlorophenol and 2,4-dichlorophenol are studied in acetonitrile solution at platinum electrodes. The photoelectrochemical reduction follows a CE-type mechanism with the electrochemical step being the formation of dihydrogen. The photochemistry arises from the excitation of the chlorophenolate anion with subsequent loss of chloride, so suggesting green routes based on photons and electricity only, applicable in both aqueous and non-aqueous solution for the dechlorination of chlorophenols.

Journal Article↗