Materials Research Group, Department of Mechanical Engineering & Material and Molecular Modelling, King's College London, London, WC2R 2LS, UK.
Phys Chem Chem Phys. 2012 May 7;14(17):5935-44. doi: 10.1039/c2cp00013j. Epub 2012 Mar 22.
Silica nanopores are the focus of significant scientific interest due to their potential in a wide variety of applications including desalination membranes. In this paper, the results of extensive all-atom molecular dynamics simulations of the electro-osmotic flow of 0.5 M monovalent (NaCl) and divalent (CaCl(2)) ionic solutions through cylindrical charged silica nanopores are presented. The silica nanopores are produced such that they capture the experimentally observed interfacial properties. The results provide an atomistic description of the ion transport through pores of diameters of 1.5 nm, 2.0 nm, 2.5 nm and 3.0 nm. In doing so, the effect of pore size on ion pairing, ion hydration, and water orientation for each ionic solution was investigated. Also, the transport of the ions through the nanopores is studied, and it is found that in the monovalent solutions the Cl(-) ions are excluded from the nanopores of all sizes. Whereas in the divalent solutions, there is no such preferential exclusion of either ion. This is due to the fact that the interfacial charge is fully compensated for by the Ca(2+) ions while it is not the case for the Na(+) ions.
由于纳米孔在各种应用中的潜力，如脱盐膜，因此硅纳米孔是当前科学研究的热点。在本文中，我们对 0.5M 单价（NaCl）和二价（CaCl2）离子溶液通过圆柱形带电硅纳米孔的电渗流进行了广泛的全原子分子动力学模拟。硅纳米孔的产生方式使其能够捕捉到实验观察到的界面特性。结果提供了对直径为 1.5nm、2.0nm、2.5nm 和 3.0nm 的孔中离子传输的原子描述。通过这种方式，研究了孔径对每种离子溶液中离子配对、离子水合和水取向的影响。此外，还研究了离子通过纳米孔的传输，发现单价溶液中的 Cl-离子被所有尺寸的纳米孔排斥。而在二价溶液中，则不存在这种对任何离子的优先排斥现象。这是由于界面电荷被 Ca2+离子完全补偿，而 Na+离子则不是这样。
