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

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