Spectroelectrochemical study of the reductive desorption and the oxidative redeposition of a monolayer of 1-hexadecanethiols chemisorbed on gold(111).

Abstract

We present a spectroelectrochemical study of the reductive desorption and the oxidative redeposition of a monolayer of 1-hexadecanethiols on Au(111) in an aqueous alkaline electrolyte solution. The solvent/thiol interactions were found to play an important role in the electrodeposition of self-assembled monolayers of low-solubility thiols. The orientation of the alkane chains in a monolayer remains unchanged after its reductive desorption and oxidative redeposition. The reductive desorption/oxidative redeposition of low-solubility thiols on Au(111) proceed through a two step mechanism. The first step of the reductive desorption is ascribed to the reduction of chemisorbed thiols. The second step of the reductive desorption occurs at a more negative potential and is assigned to the reorientation of the monolayer of physisorbed thiolates into micelles. The unblocking of the Au(111) surface caused by this reorientation of the thiolates allows the formation of an electrical double layer. (Abstract shortened by UMI.)