Structural Change in 4-Pyridineethanethiolate Self-Assembled Monolayers on Au(111) Induced by Protonation of Pyridine Ring in Electrolyte Solutions

摘要

Self-assembled monolayers (SAMs) of 4-pyridineethanethiol (4-PyEtS) formed on a Au surface was investigated by cyclic voltammetry (CV), surface enhanced infrared spectroscopy (SEIRAS), and in situ scanning tunneling microscopy (STM). On the basis of reductive desorption for 4-PyEtS on Au(111), the peak potential was observed at -0.86V vs. Ag/AgCl (sat. KCl). The surface excess was calculated to be 5.4×10{sup}(-10)mol cm{sup}(-2) from the CV, High-resolution STM images revealed that p(5×3{sup}(1/2) R-30°) lattice including two molecules was found in 0.1M NaClO{sub}4, whereas the 4-PyEtS-SAMs formed p(10×3{sup}(1/2) R-30°) lattice constituted from four molecules in 0.05 M HClO{sub}4. By the analysis of SEIRA spectra, the b axis of pyridine ring of 4-PyEtS-SAMs formed on an evaporated Au film electrode in 0.1M NaClO{sub}4 was tilted to the electrode. In contrast, that in 0.1M HCl was parallel to the surface.