Surface effects on ionic Coulomb blockade in nanometer-size pores

TL;DR

This study uses all-atom molecular dynamics to explore how atomic-scale pore wall structure affects ionic Coulomb blockade in nanopores, revealing effects of pore size, position, and length on ionic transport and resistance.

Contribution

It provides new insights into atomic-level influences on ionic Coulomb blockade and introduces an effective kinetic model to describe this phenomenon.

Findings

Pore selectivity varies with diameter and position.

Ionic transport occurs via hopping over discretized states.

Pore resistance depends on length but not on ion molarity.

Abstract

Ionic Coulomb blockade in nanopores is a phenomenon that shares some similarities but also differences with its electronic counterpart. Here, we investigate extensively this phenomenon using all-atom molecular dynamics of ionic transport through nanopores of about one nanometer in diameter and up to several nanometers in length. Our goal is to better understand the role of atomic roughness and structure of the pore walls in the ionic Coulomb blockade. Our numerical results reveal the following general trends. First, the nanopore selectivity changes with its diameter, and the nanopore position in the membrane influences the current strength. Second, the ionic transport through the nanopore takes place in a hopping-like fashion over a set of discretized states caused by local electric fields due to membrane atoms. In some cases, this creates a slow-varying "crystal-like" structure of ions inside the nanopore. Third, while at a given voltage, the resistance of the nanopore depends on its length, the slope of this dependence appears to be independent of the molarity of ions. An effective kinetic model that captures the ionic Coulomb blockade behavior observed in MD simulations is formulated.