Formation and novel functions of self-assembled monolayers of thiol derivatives

A self-assembly (SA) technique has been very widely used to construct ordered molecular layers of various functionalities on a solid substrate and self-assembled monolayers (SAMs) of alkylthiols on gold have been the most well studied system. In this article, the SA process and typical functionalities of the SAMs of thiol derivatives are described mainly based on the results obtained in our group over the last 10 years. The structure and mass transport during the self-assembly process of the thiol derivatives on Au(111) were investigated by quartz crystal microbalance (QCM) measurement, polarization modulation Fourier transform infrared spectroscopy (PM-FTIR) and scanning tunneling microscopy (STM). The electrochemical characteristics and related mass transport and structural changes of the SAMs were carefully examined. The SAMs with novel functions such as uni-directional electron transfer, electrochemically generated chemiluminescence (ECL), visible light induced uphill electron transfer, and electrochemically controllable SHG activity were constructed. Finally, future prospects are presented.