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Effects of tert-Butyl Alcohol on Water at the Liquid–Vapor Interface: Structurally Bulk-like but Dynamically Slow Interfacial Water
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2018-04-06 00:00:00 , DOI: 10.1021/acs.jpcc.7b10219
Banshi Das 1 , Bikramjit Sharma 1 , Amalendu Chandra 1
Affiliation  

We have investigated the effects of tert-butyl alcohol (TBA) on the structure and dynamics of water at the liquid–vapor interface. The structure of interfacial water has been studied by calculating the structural correlations and vibrational sum frequency generation (VSFG) spectrum from molecular dynamics simulations. It is found that the dangling peak of the VSFG spectrum of the air–water interface near ∼3700 cm–1 almost disappears in presence of TBA at the chosen concentration which means that the interfacial region is covered by the solute molecules. The hydrogen-bonded peak in the VSFG spectrum is found to be red-shifted by ∼100 cm–1 as compared to that of pure the air–water interface despite the fact that the strength of hydrogen bonds in the interfacial region is found to be similar to that of the bulk. This red shift in the VSFG spectrum is found to be a consequence of the cancellation of the nonlinear responses from “up-” and “down”-oriented O–H modes of water in that region. The local structure around the interfacial water is found to be similar to that of bulk water where the oxygen of TBA provides an environment similar to the oxygen of water in the bulk. However, the dynamical properties like the orientational relaxation and vibrational spectral diffusion are found to slow down when one moves from bulk toward the TBA layer at the surface. The effects of intra- and inter-molecular coupling and third-order susceptibility on the VSFG spectrum are also discussed.

中文翻译:

丁基醇对液-汽界面处水的影响:结构类似体积但动态缓慢的界面水

我们已经研究了丁醇(TBA)对液-气界面处水的结构和动力学的影响。通过从分子动力学模拟计算结构相关性和振动和频率生成(VSFG)谱,研究了界面水的结构。发现在选定浓度的TBA存在下,空气-水界面的VSFG谱的悬空峰在〜3700 cm –1附近几乎消失了,这意味着界面区域被溶质分子覆盖。发现VSFG光谱中的氢键峰出现了红移约100 cm –1与纯空气-水界面相比,尽管发现界面区域中的氢键强度与整体中的氢键强度相似。发现VSFG光谱中的这种红移是由于该区域中水的“上”和“下”取向的O–H模式的非线性响应被抵消的结果。发现界面水周围的局部结构与散装水的局部结构相似,其中TBA的氧气提供的环境类似于散装中的水的氧气。然而,当人们从表面上的本体向TBA层移动时,诸如定向弛豫和振动谱扩散的动力学特性会减慢。还讨论了分子内和分子间的偶联以及三阶磁化率对VSFG光谱的影响。
更新日期:2018-04-06
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