Electrochemically Assisted Self-Assembly of Alkylthiosulfates and Alkanethiols on Gold: The Role of Gold Oxide Formation and Corrosion

Electrochemically directed self-assembly of alkylthiosulfates enables the selective formation of monolayers on gold surfaces. These monolayers are identical to those formed from the corresponding alkanethiols. However, the mechanistic details of monolayer formation under electrochemical conditions as well as the role of other variables and residual water in the solvent have not been extensively studied. A systematic investigation shows that self-assembly is not a result of an outer-sphere one-electron oxidation of alkylthiosulfate. Voltammetry and electrochemical quartz crystal microbalance techniques reveal that self-assembly involving alkylthiosulfates as well as alkanethiols under oxidative conditions proceed through direct reaction with gold oxide and in some cases is accompanied by corrosion. X-ray photoelectron spectroscopy indicates that monolayers can undergo rapid exchange with molecules in solution under electrochemically directed self-assembly conditions.