多层石墨烯纳米孔中碎片脱水的离子选择性和过滤
Ionic selectivity and filtration from fragmented dehydration in multilayer graphene nanopores
摘要：
选择性离子转运是生物离子通道行为的标志，但对人工膜的工程设计是一个重大挑战。在这里，我们证明，与全原子分子动力学模拟，裸露的石墨烯纳米孔产生可测量的离子选择性，变化超过一至两个数量级，简单地通过改变孔半径和石墨烯层的数量。单层石墨烯不显示脱水诱导的选择性，直到孔半径小到足以将第一水合层从孔内部排除。然而，双层和三层石墨烯对于几乎不侵入第一水合层的孔径已经显示出这种选择性，这是由于来自第二水合层的更显著的水损失。从第一和第二水化层屏障测量选择性和活化屏障将有助于阐明生物离子通道的行为。此外，负责选择性的能垒-虽然在水合能的尺度上很小-已经相对较大，即，许多$k_B$。因此，为了从水中分离离子，可以将较长、较大半径的孔交换为较短、较小半径的孔，从而提供了一种用于保持排阻效率同时增强其他性能（例如，水通量）。
英文摘要：
Selective ion transport is a hallmark of biological ion channel behavior but is a major challenge to engineer into artificial membranes. Here, we demonstrate, with all-atom molecular dynamics simulations, that bare graphene nanopores yield measurable ion selectivity that varies over one to two orders of magnitude simply by changing the pore radius and number of graphene layers. Monolayer graphene does not display dehydration-induced selectivity until the pore radius is small enough to exclude the first hydration layer from inside the pore. Bi- and tri-layer graphene, though, display such selectivity already for a pore size that barely encroaches on the first hydration layer, which is due to the more significant water loss from the second hydration layer. Measurement of selectivity and activation barriers from both first and second hydration layer barriers will help elucidate the behavior of biological ion channels. Moreover, the energy barriers responsible for selectivity -- while small on the scale of hydration energies -- are already relatively large, i.e., many $k_B$. For separation of ions from water, therefore, one can exchange longer, larger radius pores for shorter, smaller radius pores, giving a practical method for maintaining exclusion efficiency while enhancing other properties (e.g., water throughput).
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