Electrochemistry at Ultramicroelectrode Arrays and Nanoelectrode Ensembles of Macro‐ and Ultramicroelectrode Dimensions

Abstract

AbstractRecent experiments on the development and characterization of nanoelectrode ensembles (NEEs) based on Au‐filled polycarbonate membranes and microfabricated addressable ultramicroelectrode (UME) arrays are described. Macro‐NEEs operate under primarily transient diffusion conditions while the more recently developed ultramicro‐NEEs operate under primarily steady‐state diffusion conditions due to the high rate of mass transport to the nanoelectrode sites and the overall ultramicro‐geometry; both types of NEEs are discussed. In addition to the traditional characterization methods of scanning electron microscopy (SEM) and cyclic voltammetry (CV) for arrays and ensembles, the use of scanning electrochemical microscopy (SECM) in assessing the viability of the insulated addressing tracks, as well as the electrochemical reactivity and conductivity of the individual UME sites, is discussed. The behavior of infinite (i. e., macro‐) arrays and ensembles of UME and NE sites is well understood, but this is not the case for finite (i. e., ultramicro‐) arrays and ensembles, where the perimeter sites now play a large role in the overall steady‐state behavior. A general theory and 3D simulations for these UME‐NEEs are described.