Structure Evolution of Aromatic-Derivatized Thiol Monolayers on Evaporated Gold

Abstract

The structure of self-assembled monolayers of thiophenols ( I ), benzyl mercaptans ( II ), biphenylthiols ( III ), and 4-biphenylmethanethiols ( IV ) on the surface of Au(111) are compared using cyclic voltammetry, reflection absorption infrared spectroscopy, scanning tunneling microscopy, ellipsometry and contact angle measurement. The results suggest that benyzyl mercaptans and 4-biphenylmethanethiols form closely packed and ordered monolayer, irrespective of the length of a p -alkoxy substituent. For thiophenol and biphenylthiol, a film of lower surface coverage was formed. A long p -alkoxy chain ( n -C 16 H 33 O) increases the intermolecular interaction and leads to a closer packing within the monolayer film. The difference is attributed to the interplay between intermolecular interaction and the bond angle preference at the thiolate head group.