Department of Physics, Zhejiang Normal University, Jinhua 321004, China.
J Chem Phys. 2013 May 28;138(20):204710. doi: 10.1063/1.4807383.
Using molecular dynamics simulations, we have investigated the impact of the ice-like water monolayer inside the tube and nearest to the tube wall on the diffusion properties of other inner water shells confined within a charged nanotube. We find that the axial diffusion coefficient of the first water monolayer near the wall monotonously decreases with the charge size on the nanotube, indicating a tighter control of the first monolayer from the larger sized charge. However, for the other water shells, the diffusion coefficients increase when the charge is larger than a critical value qc (~1.0 e). This unexpected phenomenon is attributed to the decreased number of hydrogen bonds between the first monolayer and other inner water shells caused by the very unique hydrogen-bond network patterns in the first ice-like monolayer, which makes it behave like a "hydrophobic water layer." Our findings may have implications for water treatment, non-fouling surfaces, catalysis engine, and biological sensor.
使用分子动力学模拟，我们研究了管内和管壁附近冰状单水分子层对受限在带电纳米管内的其他内层水分子壳扩散性质的影响。我们发现，靠近管壁的第一层水的轴向扩散系数随纳米管上电荷的大小单调减小，表明从较大尺寸的电荷对第一层的控制更紧密。然而，对于其他水壳层，当电荷大于临界值 qc（约 1.0 e）时，扩散系数增加。这种出乎意料的现象归因于由于第一层非常独特的冰状单分子层中氢键网络模式，第一层与其他内层水分子之间氢键的数量减少，使它表现得像一个“疏水水层”。我们的发现可能对水处理、防污表面、催化引擎和生物传感器有影响。
