Li Jingyuan, Liu Ting, Li Xin, Ye Lei, Chen Huajun, Fang Haiping, Wu Zhaohui, Zhou Ruhong
Department of Physics, Zhejiang University, Hangzhou 310027, China.
J Phys Chem B. 2005 Jul 21;109(28):13639-48. doi: 10.1021/jp044090w.
The dynamics of water near the nanoscale hydrophobic (graphite-CH(3)) and hydrophilic (graphite-COOH) plates has been studied in detail with molecular dynamics simulations in this paper. It is shown that these designed surfaces (by growing a layer of methyl or carboxyl groups on top of graphite) can have a significant impact on the neighboring water dynamics, with the hydrophilic carboxyl surface having even more profound effects. The water hydrogen bond lifetime is much longer near both types of surfaces than that in the bulk, while on the other hand the water diffusion constant is much smaller than that in the bulk. The difference in the diffusion constant can be as large as a factor of 8 and the difference in the hydrogen bond lifetime can be as large as a factor of 2, depending on the distance from the surface. Furthermore, the water molecules in the first solvation shell of surface atoms show a strong bias in hydroxyl group orientation near the surface, confirming some of the previous findings. Finally, the possible water dewetting transition between two graphite-CH(3) plates and the effect of the strength of the solute-solvent attractions on the water drying transition are investigated. The relationship among the dewetting transition critical distance, van der Waals potential well depth, and water contact angle on the graphite-CH(3) surface is also analyzed on the basis of a simple macroscopic theory, which can be used to predict the dewetting transition critical distance.
本文通过分子动力学模拟详细研究了纳米级疏水（石墨 - CH(3)）和亲水（石墨 - COOH）板附近水的动力学。结果表明，这些设计的表面（通过在石墨顶部生长一层甲基或羧基）会对相邻水的动力学产生显著影响，其中亲水的羧基表面影响更为深远。在这两种类型的表面附近，水的氢键寿命都比在本体中长得多，而另一方面，水的扩散常数比在本体中小得多。扩散常数的差异可能高达8倍，氢键寿命的差异可能高达2倍，这取决于与表面的距离。此外，表面原子第一溶剂化壳层中的水分子在靠近表面处的羟基取向表现出强烈的偏向性，证实了先前的一些发现。最后，研究了两个石墨 - CH(3)板之间可能的水脱湿转变以及溶质 - 溶剂吸引力强度对水干燥转变的影响。还基于一个简单的宏观理论分析了石墨 - CH(3)表面上脱湿转变临界距离、范德华势阱深度和水接触角之间的关系，该理论可用于预测脱湿转变临界距离。
