Ionic Current Rectification through Silica Nanopores

Nanopores immersed in electrolytic solution and under the influence of an electric field can produce ionic current rectification, where ionic currents are higher for one voltage polarity than for the opposite polarity, resulting in an asymmetric current−voltage (I−V) curve. This behavior has been observed in polymer- and silicon-based nanopores as well as in theoretically studied continuum models. By means of atomic level molecular dynamics (MD) simulations, we have performed a systematic investigation of KCl conductance in silica nanopores with a total simulation time of 680 ns. We found that ion-binding spots at the silica surfaces, such as dangling atoms, have effects on the ion concentration and electrostatic potential inside the nanopore, producing asymmetric I−V curves. Conversely, silica surfaces without ion-binding spots produce symmetric I−V curves.

浸没于电解液中且受电场作用的纳米孔（Nanopores）可产生离子电流整流（Ionic current rectification）现象：某一电压极性下的离子电流高于相反极性下的离子电流，进而形成不对称电流-电压（I-V）曲线。该现象已在聚合物基与硅基纳米孔，以及经理论研究的连续介质模型（continuum models）中被观测到。本研究借助原子级分子动力学（MD）模拟，对二氧化硅纳米孔中的氯化钾（KCl）电导开展了系统性研究，总模拟时长达680纳秒。研究发现，二氧化硅表面的离子结合位点（ion-binding spots）——如悬垂原子（dangling atoms）——会对纳米孔内的离子浓度与静电势产生影响，进而生成不对称I-V曲线；反之，无离子结合位点的二氧化硅表面则会形成对称I-V曲线。