Ion transport through confined ion channels in the presence of immobile charges

TL;DR

This paper investigates how ion transport in nanoscale confined channels is affected by immobile charges and external electric fields, revealing non-monotonic current behavior and supporting experimental observations through analytic and simulation methods.

Contribution

It provides a combined analytic and Monte Carlo simulation approach to explain ion transport behavior in confined channels with immobile charges, aligning with recent experimental results.

Findings

Ion current exhibits non-monotonic dependence on ion concentration.

Analytic models effectively describe ion transport at low electric fields.

Simulation results support experimental measurements of ion flow.

Abstract

We study charge transport in an ionic solution in a confined nanoscale geometry in the presence of an externally applied electric field and immobile background charges. For a range of parameters, the ion current shows non-monotonic behavior as a function of the external ion concentration. For small applied electric field, the ion transport can be understood from simple analytic arguments, which are supported by Monte Carlo simulation. The results qualitatively explain measurements of ion current seen in a recent experiment on ion transport through a DNA-threaded nanopore (D. J. Bonthuis et. al., Phys. Rev. Lett, vol. 97, 128104 (2006)).