Multiple voltammetric waves for reductive desorption of cysteine and 4-mercaptobenzoic acid monolayers self-assembled on gold substrates

The reductive desorption of cysteine and 4-mercaptobenzoic acid monolayers formed on polycrystalline and single-crystalline gold substrates has been investigated. Three cathodic waves observed at polycrystalline gold electrodes are correlated with reductive desorption from each small domain of the low index faces, i.e. (111), (100) and (110), over the surface. The stability of the adsorbates differs substantially depending on the surface crystallographic orientation, in the order (111) < (100) < (110). Thus, the reductive desorption occurs at certain potentials, leading to an apparent peak separation on their cyclic voltammograms. Partial desorption of the adsorbate via control of the potential would be a simple and reliable method of fabricating functional electrodes designed for use as electrocatalysts or sensors, on which only the small domains of the (111) face could be selectively exposed to an electrolyte.