Determination of ultramicroelectrode array dimensions at graphite and one-dimensional organic conductor electrodes using simulations, chronocoulometry and chronoamperometry

Abstract

The dimensions of ultramicroelectrode arrays at graphite and tetrathiafulvalene-tetracyanoquinodi-methane (TTF-TCNQ) electrodes were determined using a combination of chronoamperometry and a least squares optimization method which was used to fit simulated chronoamperometric responses to experimental data. The ultramicroelectrode array dimensions obtained from the fit were verified with chronocoulometry. The ultramicroelectrode array dimensions obtained for electrochemically treated TTF-TCNQ/poly(vinyl chloride) polymer paste electrodes are consistent with a transition from semi-infinite linear diffusion at slow scan rates to radial diffusion characteristic of ultramicroelectrode arrays at fast scan rates in plots of cyclic voltammetric peak currents vs. scan rate. Scanning electron micrographs of copper electrodeposited on these surfaces support the results obtained by chonoamperometry revealing the random structure of the ultramicroelectrode array. Chronoamperometric and chronocoulometric responses at polished TTF-TCNQ/poly(vinyl chloride), untreated glassy carbon and rough pyrolytic graphite electrodes do not reveal the presence of ultramicroelectrode array behavior. Scanning electron micrographs of electrodeposited copper on polished TTF-TCNQ/poly(vinyl chloride) electrodes demonstrate that the dimensions of the ultramicroelectrode array are too small to be resolved by the methods used. Chronocoulometric responses at electrochemically treated glassy carbon electrodes suggest the presence of a microhole array.