Electron transport through alkanethiolate films decorated with monolayer protected gold clusters

Monolayers of 1,9-nonanedithiol or 1-decanethiol self-assembled directly on the gold substrate transfer charge to the K4[Fe(CN)6] molecule in solution more efficiently when they are decorated with 1-butanethiol protected gold nanoclusters. The clusters bound to the electrode by means of dithiol are more uniformly distributed on the monolayer and their efficiency in transferring electrons between the electrode and the redox couple is higher than when they are simply adsorbed through weak van der Waals interactions with the methyl groups of 1-decanethiol. With increasing adsorption time in the solution of clusters, the capacitance of the cluster decorated electrode significantly increases compared to the constant value of capacitance observed after prolonged immersion in pure toluene. This difference is explained assuming that gold clusters act as an array of capacitors on the monolayer modified electrode surface.