Salt effect on molecular orientation at air/liquid methanol interface
Salt effect on molecular orientation at air/liquid methanol interface
复制标题
盐对空气/液体甲醇界面分子取向的影响
DOI：
10.1016/j.cclet.2016.01.004
复制
发表时间：
2016-04-01
影响因子：
9.1
通讯作者：
Guo, Yuan
中科院分区：
文献类型：
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作者：
Li, Xia;Deng, Gang-Hua;Guo, Yuan
采用极化相关和频产生振动谱（SFG-VS）研究了盐对空气/液甲醇界面分子取向的影响。我们澄清了甲基的平均倾斜角为θ = 30度+/- 5度在空气/纯甲醇表面假设一个三角函数取向分布。在加入3mol /L的NaI后，甲基向表面法线进一步倾斜，新的θ = 41°+/- 3°。这种取向变化并不能解释添加NaI时SFG-VS强度的增强，这意味着表面区域净极性有序的甲醇分子的数量密度也随着NaI浓度的变化而变化。这些光谱发现揭示了盐对极性有机溶液表面结构的影响。研究还表明，准确测定不同盐浓度下的体折射率和拉曼退极化比对于定量解释SFG-VS数据至关重要。(C) 2016年中国化学学会，中国医学科学院药物研究所。Elsevier B.V.版权所有。
The salt effects on molecular orientation at air/liquid methanol interface were investigated by the polarization-dependent sum frequency generation vibrational spectroscopy (SFG-VS). We clarified that the average tilting angle of the methyl group to be theta = 30 degrees +/- 5 degrees at the air/pure methanol surface assuming a delta-function orientational distribution. Upon the addition of 3 mol/L NaI, the methyl group tilts further away from the surface normal with a new theta = 41 degrees +/- 3 degrees. This orientational change does not explain the enhancement of the SFG-VS intensities when adding NaI, implying the number density of the methanol molecules with a net polar ordering in the surface region also changed with the NaI concentrations. These spectroscopic findings shed new light on the salt effects on the surfaces structures of the polar organic solutions. It was also shown that the accurate determination of the bulk refractive indices and Raman depolarization ratios for different salt concentrations is crucial to quantitatively interpret the SFG-VS data. (C) 2016 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.