Sung Jaeho, Park Kyungsu, Kim Doseok
Department of Physics and Interdisciplinary Program of Integrated Biotechnology, Sogang University, Seoul 121-742, Korea.
J Phys Chem B. 2005 Oct 6;109(39):18507-14. doi: 10.1021/jp051959h.
Sum-frequency generation vibrational spectroscopy was used to investigate the surface molecular structure of binary mixtures of water and alcohol (methanol, ethanol, and propanol) at the air/liquid interface. In this study, it is shown that the sum-frequency signal from the alcohol molecules in the CH-stretch vibration region is always larger for mixtures than that from pure alcohol. For example, the sum-frequency signal from a propanol mixture surface at a 0.1 bulk mole fraction was approximately 3 times larger than that from a pure propanol surface. However, the ratio between the sum-frequency signals taken at different polarization combinations was found to be constant within experimental errors as the bulk alcohol concentration was changed. This suggested that the orientation of surface alcohol molecules does not vary appreciably with the change of concentration and that the origin of the signal enhancement is mainly due to the increase in the surface number density of alcohol molecules contributing to the sum-frequency signal for the alcohol/water mixture as compared to the pure alcohol surface.
利用和频振动光谱研究了空气/液体界面处水与醇（甲醇、乙醇和丙醇）二元混合物的表面分子结构。本研究表明，在CH伸缩振动区域，混合物中醇分子的和频信号总是大于纯醇的和频信号。例如，在本体摩尔分数为0.1时，丙醇混合物表面的和频信号约为纯丙醇表面的3倍。然而，随着本体醇浓度的变化，在不同偏振组合下测得的和频信号之间的比值在实验误差范围内保持恒定。这表明表面醇分子的取向不会随浓度变化而明显改变，信号增强的原因主要是与纯醇表面相比，醇/水混合物中对和频信号有贡献的醇分子表面数密度增加。
