Molecular orientation of self-assembled monolayer of octadecanethiol on platinum surface studied by femtosecond broad-bandwidth sum frequency generation spectroscopy

Abstract

The molecular orientation in self-assembled monolayer (SAM) of octadecanethiol (ODT) on platinum surface prepared in ethanol solution was examined by broad-bandwidth sum frequency generation (BB-SFG) spectroscopy. The bands attributed to the CH3 symmetric and asymmetric stretching vibrational modes were observed in the SFG spectra. From the analysis of SFG intensity ratio of these two modes, the alkyl chain on platinum was found to be more perpendicular to the substrate than those on gold surface. Copyright © 2005 The Chemical Society of Japan.