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Effects of Surface Trapping and Contact Ion Pairing on Ion Transport in Nanopores
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2019-06-11 , DOI: 10.1021/acs.jpcc.9b02972
Zhongwu Li 1 , Yinghua Qiu 2 , Yan Zhang 1 , Min Yue 1 , Yunfei Chen 1
Affiliation  

Ion transport in highly confined space is important to various applications, such as biosensing and seawater desalination with nanopores. All-atom molecular dynamics simulations are conducted to investigate the transport of Na+ and Cl ions through nanopores with the diameter below 6 nm. It is found that the formation of the contact ion pair plays a critical role in reducing the ion mobility inside a nanopore without surface charges. The mobility for both cations and anions decreases with the reduced pore size because it is easier to form the contact ion pairs inside the neutral nanopore with a smaller diameter. Inside a charged nanopore, besides the contact ion pair formation, the surface charges also play a significant role in reducing the counterion mobility through surface trapping. It is uncovered that the mobility of Na+ ions increases first and then decreases with the surface charge density, while Cl ions have the opposite trend. A modified first-passage time model is proposed to take into account the ion pair formation and the trapped ions inside a nanopore, which provides a clear picture in describing ion transport through a nanopore.

中文翻译:

表面陷阱和接触离子对对纳米孔中离子迁移的影响

高度受限空间中的离子传输对于各种应用至关重要,例如生物传感和纳米孔海水淡化。全原子分子动力学模拟,以调查的Na的运输+和Cl -离子通过直径小于6 nm的纳米孔。发现接触离子对的形成在减小没有表面电荷的纳米孔内部的离子迁移率中起关键作用。阳离子和阴离子的迁移率都随着孔径的减小而降低,因为更容易在直径较小的中性纳米孔内形成接触离子对。在带电荷的纳米孔内部,除了形成接触离子对以外,表面电荷还通过表面捕获在降低抗衡离子迁移率方面起着重要作用。研究发现,Na +离子的迁移率随表面电荷密度的增加先增大,然后减小,而Cl 离子具有相反的趋势。提出了一种经过修改的首次通过时间模型,以考虑离子对的形成和纳米孔内部的被困离子,这为描述离子通过纳米孔的传输提供了清晰的画面。
更新日期:2019-06-11
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