An indirect laser-induced temperature jump study of the influence of redox couple adsorption on heterogeneous electron transfer kinetics

The indirect laser-induced temperature jump technique is used to study the heterogeneous electron transfer kinetics of Fe(CN)63−/4−, Ru(NH3)63+/2+ (both in aqueous 1 M KF) and dimethylferrocene/dimethylferrocenium (Me2Fc, in 1 M LiClO4 in CH3OH) on Au electrodes. Evidence is obtained demonstrating not only that all three of these redox couples adsorb on Au but also that the behavior of the measured electron transfer kinetics for these couples is significantly perturbed from that expected for simple heterogeneous electron transfer reactions. The interpretation of the results of these measurements is, therefore, made much more complex and uncertain. Such complexity and uncertainty is greatly reduced by irreversibly attaching the redox moiety to the electrode surface as a part of a stable, organized structure (e.g. a self-assembled monolayer).