The self-assembling process of ferrocenylundecanethiol on a gold surface has been measured in situ using the electrochemical quartz crystal microbalance (EQCM). Initial adsorption was fast and was followed by the slow adsorption whose rate was 2 orders of magnitude smaller. The number of adsorbed thiol molecules, estimated from the frequency change, suggests the formation of the monomolecular layer of the thiol. This number agrees well with that calculated from the electrochemical charge associated with oxidation/reduction of the monolayer in 1 M HClO4. The EQCM was also used to follow the mass change during the oxidation/reduction of the ferrocenylundecanethiol monolayer. It was confirmed that anions are incorporated into the self-assembled layer upon oxidation of the ferrocene group.
