表面增强拉曼光谱研究吸附态的变化

Study on Adsorbed States by Surface Enhanced Raman Spectroscopy

测量了吡啶分子在电化学处理的银表面和亚甲基蓝分子在硝酸刻蚀银表面的表面增强拉曼光谱（ＳＥＲＳ）．对ＳＥＲＳ谱线的分析结果表明，吡啶分子在较低的表面吸附分子密度时倾向于平躺方式；而在较高的表面分子密度时，则倾向于向垂直吸附态转化．亚甲基蓝分子在较低浓度时主要是平躺吸附，随Ｃｌ－浓度的增加，亚甲基蓝从“平躺”吸附态转向“站立”吸附态．

SERS has been used as a state resolved probe to study the adsorbed states. In the case of pyridine adsorption on Ag electrode surface, the equilibrium and transitions between two adsorbed states, the perpendicular mode adsorbed through the nitrogen lone pair electrons and the flat mode through the π electrons of the aromatic ring, were studied. It was found that in the low pyridine concentration or the initial stage of adsorption, the flat mode was favored. While the concentration became higher and the adsorption tended to equilibrium, the adsorbate molecules would transit to the perpendicular mode. The effects of other factors such as the electrical potential and the pH value of the solution were also investigated. In the case of the adsorption of methylene blue on the HNO 3 etched silver surface, adding Cl - ions could promote a transition of adsorbed MB molecules from “lying down' state to “end on' state.