Adsorption of self-assembling sulfur compounds through electrochemical reactions: Effects of potential, acid and oxidizing agents

Abstract

Adsorption of organosulfur compounds forming self-assembled monolayers (SAM) on gold was studied to examine the effects of the electrical potential, added redox couple and acidity of the solution on the rate and extent of adsorption. Also, by comparing behavior of the open-circuit potentials of platinum to those of gold and silver substrates, it was confirmed that no electrochemical reaction takes place for chemisorption of the organic sulfur compounds on a Pt surface whereas anodic (in the case of thiols) or cathodic (in the case of dialkyl disulfides) reactions occur during adsorption on gold and silver. From an acid solution, the oxidative adsorption of a thiol was retarded, whereas the reductive-dissociative adsorption of a disulfide was facilitated. Added ferrocene–ferrocenium redox couple enhanced adsorption of the thiol by maintaining the potential of the substrate high, thus providing a convenient way to help the formation of adsorbed layers.