Electrochemical properties of alkanethiol self-assembled monolayer on gold

Abstract

This work utilized the advantages of Electrochemical Impedance Spectroscopy (EIS) and other analytical techniques to study topics related to self-assembled monolayer (SAM) of alkanethiol on gold. Electron transfer kinetics across alkanethiol SAM was studied. Electron transfer coefficient and electron tunneling coefficient values were obtained using EIS measurement and the Marcus theory was verified. The potential profile across the interface of SAM covered electrodes was studied. Carboxylate terminated SAM was studied with EIS and the pKa value was obtained. An unknown feature in the Cyclic Voltammogram of alkanethiol SAM in inert electrolyte was observed and studied. Possible causes were proposed, namely the flow of charge through defects in the SAM or an oxygen reduction reaction. Electrochemical STM study shows mild dc potential does not affect the properties of the SAM. Mixed alkanethiol SAM was studied with EIS and accurate quantitative information of the composition were obtained. This facilitated the study of the adsorption thermodynamics and kinetics of the mixed SAM. It was found that alkanethiol adsorbed on gold can be replaced at the early stages of SAM formation.