A SURFACE ANALYTICAL AND AN ELECTROCHEMICAL STUDY OF IRON SURFACES MODIFIED BY THIOLS

In order to increase the chemical and electrochemical stability of metal/polymer composite materials the first monolayer of the organic coating should be bonded by chemical bonds to the substrate. In this study, the bond formation between iron and n-decanethiol has been studied by surface-sensitive techniques (XPS, AFS) and the stability of the modified surface by cyclic voltammetry in different aqueous electrolytes. Chemisorptive bonds between the substrate and the thiol could be formed probably by cleavage of the S-H bond - only, if the metal surface is free of any oxide layer. Cyclovoltammetry in nitrogen purged aqueous electrolytes enhances the package density of the adsorbed molecules and leads to a more perpendicular orientation of the thiol molecules with respect to the substrate surface. The very stable bond between iron and the thiol suppresses an oxidation of both the iron surface and the SH group in air and in electrolytes of different pH within a large potential range.