Adsorption and desorption of electroactive self-assembled thiolate monolayers on gold

The influence of different chemical pretreatments on the formation and electrochemistry of self-assembled mixed monolayers of 11-(ferrocenylcarbonyloxy)undecanethiol and n-decanethiol was examined using cyclic voltammetry (CV) and X-ray Photoelectron Spectroscopy (XPS). The "hot-etched" pretreated surface yields mixed monolayers with higher surface coverages of the electroactive thiol than a "cold-etched" surface. It is proposed that the former surface presents a greater percentage of higher energy binding sites than the latter surface. The higher stability of these sites for the ferrocenylalkanethiolate is confirmed by desorption experiments in ethanol. The electroactive species are shown to be in dynamic adsorption/desorption equilibrium with the ethanol solution, which helps to explain a number of important properties.