Ion Transport in Tapered Nanoslits

Abstract

Over the last two decades, extensive research has been conducted in the field of nanofluidics, which focuses on the transport of water and ions in nanochannels. Recent advances have allowed the fabrication of quasi two-dimensional nanoslits, which have already been shown to exhibit many fascinating properties. In this thesis, we investigate the transport phenomena inside uncharged asymmetric, tapered nanoslits. We performed extensive molecular dynamics simulations with different geometry parameters, electric field strengths and salts, all with an explicit water model. In these systems we find a slight rectification of the ionic currents. More interestingly, we observe a strong ion selectivity, and hence a nearly diodic ion flux. We attribute this to a divergence in the polarization of the water, in combination with a high water flux. We describe the interaction between the water structure, ion fluxes and water fluxes, which acts as a novel mechanism for ion selectivity in nanoslits.