School of Mechanical Engineering, Shanghai Jiao Tong University, 800 Dong Chuan Road, Shanghai, 200240, China.
J Phys Chem B. 2012 Nov 15;116(45):13459-66. doi: 10.1021/jp3076595. Epub 2012 Nov 6.
Understanding the behavior of osmotic transport across nanoporous membranes at molecular level is critical to their design and applications, and it is also beneficial to the comprehension of the mechanism of biological transmembrane transport processes. Pore density is an important parameter for nanoporous membranes. To better understand the influence of pore density on osmotic transport, we have performed systematic molecular dynamics simulations on water osmosis across nanoporous membranes with different pore densities (i.e., number of pores per unit area of membrane). The simulation results reveal that significant size effects occur when the pore density is so high that the center-to-center distance between neighboring nanopores is comparable to the solute size. The size effects are independent of the pore diameter and solute concentration. A simple quantitative correlation between pore density, solute size, and osmotic flux has been established. The results are excellently consistent with the theoretical predictions. It is also shown that solute hydration plays an important role in real osmotic processes. Solute hydration strengthens the size effects of pore density on osmotic processes due to the enlarged effective solute size induced by hydration. The influence of pore density, solute size, and solute hydration on water osmosis through nanoporous membranes can be introduced to eliminate the deviations of real osmotic processes from ideal behavior.
理解纳米多孔膜中渗透传输的分子水平行为对于其设计和应用至关重要，也有助于理解生物跨膜传输过程的机制。孔径密度是纳米多孔膜的一个重要参数。为了更好地理解孔径密度对渗透传输的影响，我们对具有不同孔径密度（即膜单位面积上的孔数）的纳米多孔膜中的水渗透进行了系统的分子动力学模拟。模拟结果表明，当孔径密度非常高，以至于相邻纳米孔的中心到中心距离与溶质尺寸相当时，会出现显著的尺寸效应。这种尺寸效应与孔径和溶质浓度无关。建立了孔径密度、溶质尺寸和渗透通量之间的简单定量关系。结果与理论预测非常吻合。还表明，溶质水合作用在实际渗透过程中起着重要作用。由于水合作用导致有效溶质尺寸增大，溶质水合作用增强了孔径密度对渗透过程的尺寸效应。可以引入孔径密度、溶质尺寸和溶质水合作用对纳米多孔膜中水渗透的影响，以消除实际渗透过程对理想行为的偏离。
