Mass transport accompanied with electron transfer between the gold electrode modified with 11-ferrocenylundecanethiol monolayer and redox species in solution — an electrochemical quartz crystal microbalance study

An electrochemical quartz crystal microbalance (EQCM) was employed to investigate mass transport during the redox reaction of the ferrocenylundecanethiolate (FeC 11 S(H)) monolayer modified gold electrode in solution containing other redox species. The FeC 11 S monolayer on gold acts as a barrier for the electron transfer between a gold electrode and Fe(CN) 6 4−/3− in solution and as a mediator for the reduction of Fe 3+ in solution. In both cases, electrochemical current responses were complicated because the observed currents were due to the redox of both the ferrocenyl group immobilized on gold and others in electrolyte solutions. The frequency change, i.e. interfacial mass change on the gold electrode surface, was observed only during the redox of ferrocenyl groups. The complex current response was deconvoluted into the current components of redox reaction of ferrocene and that of other redox species in solution by comparing cyclic voltammograms with the current calculated from frequency changes.