关键词: 和频振动光谱, 取向反转, 金电极, 乙腈

Abstract: The electrochemical interface between liquid acetonitrile and polycrystal gold electrode is investigated by in situ infrared visible sum frequency generation spectroscopy (SFG-VS). The structure of acetonitrile adsorbed at polycrystal gold electrode surface is studied as a function of electrode potential. The SFG spectra of CH3 group indicate acetonitrile orients in response to the electrode potential. The SFG signal of CH3 group turns lower as the electrode potential changes from -700mV to 300mV, and vanishes around the 300mV(pzc), then becomes a negative signal above 500mV, which indicates that the orientation is predominately with the CH3 group toward the metal between -700 and 300mV and with the CN group toward the metal above 300 mV. It is the first time to observe the flip-flop behavior of acetonitrile dipole at the polycrystal gold electrode surface, from which we may infer that the flip-flop behavior of acetonitrile is a common phenomenon.

Key words: sum frequency generation vibrational spectroscopy, flip-flop, gold electrode, acetonitrile