CORROSION OF GOLD BY ALKANE THIOLS

STM images of self assembled alkanethiol films on gold surfaces show h oles which have been identified as vacancies in the topmost gold layer . We show that this vacancy formation is accompanied by a corrosion pr ocess of gold in ethanolic thiol solutions. The amount of dissolved go ld from polycrystalline substrates as a function of immersion lime, th iol concentration, chain length and solvent has been investigated by A tomic Absorption Spectroscopy (AAS). The results suggest that the thio l molecule itself is the active oxidant. In case of a 1 mmol solution of docosanethiol in ethanol a gold concentration corresponding to 6% o f a gold monolayer has been detected after an immersion Lime of 24 h. By using hexane as a solvent the amount of dissolved gold is reduced t o less than 0.2%, indicating a strong solvent (e.g. polarity) dependen ce for the corrosion process. The kinetics of the corrosion process ha ve been measured and compared to kinetic data related to the formation of an ordered thiol film.