Self-assembled monolayers of long-chain xanthic acids on gold studied by voltammetry

A new method for the formation of xanthic acids H(CH2)nCS2H (n=8, 10, 12) in a non-polar solvent from the corresponding potassium salts was developed. It was found that the xanthic acids spontaneously adsorb onto gold electrodes, via a mechanism that is proposed to be similar to the adsorption of thiols on gold surfaces. The xanthate modified gold electrodes were studied by cyclic voltammetry. It was found that the xanthate layers efficiently block the current from a ferro/ferri redox couple in aqueous solution. Studies of the electrochemical desorption of the xanthate layer supported the fact that xanthic acids spontaneously form a self-assembled monolayer on the electrode.