The objective of this work is to determine the effects of surface microstructure on electrochemical response characteristics of the organic conducting salt tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) and graphite electrodes. Influence of mass transport and surface/substrate interactions on response is determined and a surface structure model is presented.

The effect of surface microstructure on mass transport is investigated at both TTF-TCNQ and graphite electrodes. Surface imaging and electrochemical techniques demonstrate that the surfaces of both materials can be described by a microelectrode array model where localized areas of electrochemical activity are separated by inactive regions. In the case of graphite, atomic force microscopy reveals microelectrode array structure, where surface defects act as localized areas of high electroactivity. Changes in activity resulting from electrode preparation procedures can be accounted for by changes in dimensions of the microelectrode array. The time scale over which the effects of nonlinear diffusion to individual microelectrodes is observed in transient electrochemical responses is used for determining the dimensions of microelectrode arrays at TTF-TCNQ electrodes. The dimensions of the microelectrode arrays, determined at both TTF-TCNQ and graphite electrodes, are in agreement with dimensions of copper deposits used to image electroactive sites.

The role of surface/substrate interactions in the response of TTF-TCNQ and graphite electrodes is also investigated. Mass changes at TTF-TCNQ electrodes, determined with a quartz crystal microbalance, in addition to kinetic studies, show that a TCNQ0 rich surface is produced under typical electrochemical conditions, and that TCNQ0 mediation is responsible for the catalytic behavior of TTF-TCNQ electrodes toward the oxidation of some biological molecules.

Numerical semi-integration of voltammetric responses is used to identify and quantify weak adsorption in the presence of diffusion. The utility of this method is demonstrated with p-benzoquinone which weakly adsorbs on active graphite electrodes. In addition, a thin-layer model is introduced which is consistent with weak adsorption. This model is used to demonstrate the utility of semi-integral analysis and predicts the behavior of porous thin films into which redox species partition, and predicts the behavior of new surface structure.