Center for Computational Quantum Physics, Flatiron Institute, 162 5th Avenue, New York, New York 10010, USA.
Laboratoire de Physique de l'École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, Paris, France.
J Chem Phys. 2022 Sep 21;157(11):114703. doi: 10.1063/5.0102002.
The transport of fluids at the nanoscale is fundamental to manifold biological and industrial processes, ranging from neurotransmission to ultrafiltration. Yet, it is only recently that well-controlled channels with cross sections as small as a few molecular diameters became an experimental reality. When aqueous electrolytes are confined within such channels, the Coulomb interactions between the dissolved ions are reinforced due to dielectric contrast at the channel walls: We dub this effect "interaction confinement." Yet, no systematic way of computing these confined interactions has been proposed beyond the limiting cases of perfectly metallic or perfectly insulating channel walls. Here, we introduce a new formalism, based on the so-called surface response functions, that expresses the effective Coulomb interactions within a two-dimensional channel in terms of the wall's electronic structure, described to any desired level of precision. We use it to demonstrate that in few-nanometer-wide channels, the ionic interactions can be tuned by the wall material's screening length. We illustrate this approach by implementing these interactions in Brownian dynamics simulations of a strongly confined electrolyte and show that the resulting ionic conduction can be adjusted between Ohm's law and a Wien effect behavior. Our results provide a quantitative approach to tuning nanoscale ion transport through the electronic properties of the channel wall material.
纳米尺度下的流体输运对于从神经传递到超滤等多种生物和工业过程至关重要。然而，直到最近，具有横截面小至几个分子直径的精细控制通道才成为实验现实。当水基电解质被限制在这样的通道中时，由于通道壁的介电对比，溶解离子之间的库仑相互作用得到增强：我们将这种效应称为“相互作用限制”。然而，除了完美金属或完美绝缘通道壁的极限情况之外，还没有提出系统的计算这些受限相互作用的方法。在这里，我们引入了一种新的形式主义，基于所谓的表面响应函数，用壁的电子结构来表示二维通道内的有效库仑相互作用，其描述精度可以任意提高。我们用它来证明，在几纳米宽的通道中，离子相互作用可以通过壁材料的屏蔽长度来调节。我们通过在布朗动力学模拟中实现这些相互作用来展示这种方法，结果表明，由此产生的离子传导可以在欧姆定律和维恩效应行为之间进行调整。我们的结果为通过通道壁材料的电子特性来调整纳米尺度离子输运提供了一种定量方法。
