Voltage-gated multilayer graphene nanochannel for K+/Na+ separation: A molecular dynamics study

Abstract

Biological protein channels have a series of remarkable properties such as selective ion or water transport. In this work, using molecular dynamics simulations, a bioinspired flexible graphene nanochannel were designed based on the structures and mechanisms of biological K+ channel. The results show that the graphene nanochannel stacked from six graphene nanopores with four carbonyl groups attached at the edges of each pore presents a voltage-gated K+/Na+ separation. As the increase of voltage bias, the separation performance first increases and then decreases. The potential of mean force curves for K+ and Na+ indicate that the energy barrier for K+ transport is smaller due to the easier dehydration of K+, which results in its higher ion current. Meanwhile, the hydration structures of the passing ions under different electric field intensities show that the transport of K+ through dihydrate is more efficient, which leads to the higher separation ratio. In addition, self-driven and Coulomb knock-on ion transport mechanisms are revealed. These findings provided here deepen our understanding about the mechanism of selectively ion transport in biological ion channels, and also give a general scheme for the design of flexible nanochannels that can be used in ion sensors, nanofiltration, and other related voltage-gated nanofluidic devices.