Comparative Study for Displacement of Cyclohexanethiolate and Cyclohaxaneselenolate Self- Assembled Monolayers on Au(111) by Octanethiols

Abstract

To compare the adsorption affinity of S-Au and Se-Au in self-assembled monolayers (SAMs), we examined displacement behaviors of pre-covered cyclohexanethiolate (CHS) and cyclohexaneselenolate (CHSe) SAMs on Au(111) by octanethiol (OT) for 20 min using scanning tunneling microscopy (STM) and cyclic voltammetry (CV) measurements. Molecular-scale STM observation revealed that the surface structure of CHS SAMs with a (5x2 root 3)R35 degrees packing structure on Au(111) was totally changed to a linear molecular row structure after displacement for 20 min, whereas the surface structure of CHSe SAMs with a (2x2 root 10)R27 degrees structure was almost not changed. This STM result are also good consistent with CV result showing reductive desorption behaviors. From STM and CV results, we consider that the strength of Se-Au bond in the SAMs is much stronger than that of S-Au bond.