Comparison of the performance of an array of nanoband electrodes with a macro electrode with similar overall area.

The performance of two electrode architectures with broadly similar overall active electrode areas are examined. The first is an electrode comprising a single contiguous area (a disc) and the second is an electrode in which the cumulative electrode area is dispersed over a wide area as a 50 nm thickness platinum nanoband. A direct comparison of the electrochemical performance of these two electrodes has been made. The relatively simple nanoband electrode architecture is shown to have benefits, including two orders of magnitude greater mass transport limited currents, the ability to measure faster electrode kinetics (by a similar factor), a three orders of magnitude lowering of the Limit of Detection and a significantly reduced susceptibility to hydrodynamic perturbations. The consequences and implications of these performance characteristics on the uses of such a nanoband electrode have been considered.

The development and characterisation of square microfabricated electrode systems.

This paper outlines the systematic production and characterisation of biocompatible square microfabricated electrode systems for electroanalysis. In contrast to previous results, a combination of simulation, theoretical analysis and measurement has established that there is an enhanced current density for a microsquare electrode under mass transport limiting current conditions when compared to a microdisc of equivalent size. This is not simply due to a difference in the effective areas of the electrodes as the difference is frequency (diffusion layer thickness) dependent; it can instead be attributed to the effects of enhanced diffusion at the corners of the microsquares on the growing diffusion layer.

A systematic study of the influence of nanoelectrode dimensions on electrode performance and the implications for electroanalysis and sensing.

Micron resolution photolithography has been employed to make microsquare nanoband edge electrode (MNEE) arrays with reproducible and systematic control of the crucial dimensional parameters, including array element size and spacing and nanoelectrode thickness. The response of these arrays, which can be reproducibly fabricated on a commercial scale, is first established. The resulting characteristics (including high signal and signal-to-noise, low limit of detection, insensitivity to external convection and fast, steady-state, reproducible and quantitative response) make such nanoband electrode arrays of real interest as enhanced electroanalytical devices. In particular, the nanoelectrode response is presented and analysed as a function of nanometre scale electrode dimension, to assess the impact and relative contributions of previously postulated nanodimensional effects on the resulting response. This work suggests a significant contribution of migration at the band edges to mass transfer, which affects the resulting electroanalytical response even at ionic strengths as large as 0.7 mol dm(-3) and for electrodes as wide as 50 nm. For 5 nm nanobands, additional nanoeffects, which are thought to arise from the fact that the size of the redox species is comparable to the band width, are also observed to attenuate the observed current. The fundamental insight this gives into electrode performance is discussed along with the consequent impact on using such electrodes of nanometre dimension.