Microstructured electroactive surface based on binary self-assembled monolayer

In this paper, binary self-assembled monolayers of 12-(ferrocenylcarbonyloxy)dodecane thiol (Fc-C12SH) and dodecanethiol (C12SH) have been prepared on gold surfaces by using two step procedures and characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The first step consisted to the formation of sub-monolayer based on an insulating alkylthiolate C12SH. We examined the monolayer formation by exploring kinetics rather than thermodynamic formation conditions. Rather than creating perfect monolayer, our work focused on the formation and the control of pinholes in the monolayer. Thereafter, the modified surface was incubated in a solution containing variable proportion of C12SH and Fc-C12SH. These pinholes were used as template for the formation of micro-domain allowing studying the effects of microenvironment on the long range electrode transfer. The electrochemical responses of the ferrocyanide/ferricyanide probes were used to monitor adsorbate coverage, environment, and phase separation within each of these monolayers. We showed that the coverage of C12SH did not vary notably between 1 h and 12 h. However, the pinhole parameters changed dramatically. We observed an increase of both the radius of the pinhole ra and the distance between the centres of adjacent pinholes 2×rb2×rb with the adsorption time. This behaviour allowed us to elaborate microstructured electroactive surface.