Interfacial Water at Hydrophobic and Hydrophilic Surfaces: Slip, Viscosity, and Diffusion
Interfacial Water at Hydrophobic and Hydrophilic Surfaces: Slip, Viscosity, and Diffusion
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DOI：
10.1021/la901314b
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发表时间：
2009-09-15
期刊：
影响因子：
3.9
通讯作者：
Netz, Roland R.
中科院分区：
文献类型：
--
作者：
Sendner, Christian;Horinek, Dominik;Netz, Roland R.
通过非平衡分子动力学模拟研究了疏水和亲水金刚石表面水的动力学和结构。对于处于剪切条件下的疏水表面，一般的水动力边界条件涉及到有限的表面滑移，滑移长度的取值敏感地取决于油、地表水相互作用强度和表面粗糙度；提出了滑动长度、接触角和损耗层厚度之间的启发式标度关系。水相中的惰性气体表现出明显的表面活性，但仅轻微地增加了滑移长度。相反，在极性亲水表面上，滑移是不存在的，但发现在薄的表面层内水的粘度增加了。该表面层的粘度和厚度取决于极性表面基团的密度。表面层中单个水分子的动力学表现出类似的区别：油疏水表面的动力学纯粹是扩散的，而靠近亲水性表面的水分子在数百皮秒的时间内发生短暂的结合或捕获。我们还详细讨论了Lennard-Jones截止长度对界面性质的影响。
The dynamics and structure of water at hydrophobic and hydrophilic diamond surfaces is examined via nonequilibrium Molecular Dynamics simulations. For hydrophobic surfaces under shearing conditions, the general hydrodynamic boundary condition involves a finite surface slip, The value of the slip length depends sensitively oil the surface water interaction strength and the surface roughness; heuristic scaling relations between slip length, contact angle, and depletion layer thickness are proposed. Inert gas in the aqueous phase exhibits pronounced surface activity but only mildly increases the slip length. On polar hydrophilic surfaces, in contrast, slip is absent, but the water viscosity is found to be increased within a thin surface layer. The viscosity and the thickness of this surface layer depend on the density of polar surface groups. The dynamics of single water molecules in the Surface layer exhibits a similar distinction: oil hydrophobic surfaces the dynamics is purely diffusive, while close to a hydrophilic surface transient binding or trapping of water molecules over times of the order of hundreds of picoseconds occurs. We also discuss in detail the effect of the Lennard-Jones cutoff length on the interfacial properties.