Induced Charge Anisotropy: A Hidden Variable Affecting Ion Transport through Membranes
Induced Charge Anisotropy: A Hidden Variable Affecting Ion Transport through Membranes
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DOI：
10.1016/j.matt.2019.12.022
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发表时间：
2019-06
期刊：
影响因子：
18.9
通讯作者：
Hessam Malmir;Razi Epsztein;M. Elimelech;A. Haji-Akbari
中科院分区：
文献类型：
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作者：
Hessam Malmir;Razi Epsztein;M. Elimelech;A. Haji-Akbari
半透膜选择性地阻止不需要的溶质运输的能力是许多应用的关键。然而，由于现有实验技术的时空分辨率不足，以及传统分子模拟无法获得相关的溶质输运时间尺度，因此对膜结构如何影响选择性的系统理解仍然难以实现。在这里，我们利用跳跃前向通量采样来探测钠离子和氯离子通过具有亚纳米孔的石墨膜的传输。我们发现氯化物通过孔隙的速度比钠离子快两个数量级。我们还确定了两种离子类型运输的两个主要障碍。除了前导离子的部分脱水外，前导离子的穿越引起其后方的电荷各向异性，这对离子施加了净约束力。因此，电荷各向异性是控制离子通过纳米孔传输动力学的关键隐藏变量。
The ability of semipermeable membranes to selectively impede the transport of undesirable solutes is key to many applications. Yet obtaining a systematic understanding of how membrane structure affects selectivity remains elusive due to the insufficient spatiotemporal resolution of existing experimental techniques and the inaccessibility of relevant solute transport timescales to conventional molecular simulations. Here, we utilize jumpy forward-flux sampling to probe the transport of sodium and chloride ions through a graphitic membrane with sub-nanometer pores. We find chlorides to traverse the pore at rates over two orders of magnitude faster than sodiums. We also identify two major impediments to the transport of both ion types. In addition to the partial dehydration of the leading ion, its traversal induces charge anisotropy at its rear, which exerts a net restraining force on the ion. Charge anisotropy is therefore a crucial hidden variable controlling the kinetics of ion transport through nanopores.