Model charged cylindrical nanopore in a colloidal dispersion: charge reversal, overcharging and double overcharging

TL;DR

This study uses integral equations to analyze the ionic distributions around a charged cylindrical nanopore, revealing phenomena like overcharging, charge reversal, and introducing the novel concept of double overcharging, with implications for nanotechnology and biology.

Contribution

First prediction of overcharging in a cylindrical double layer and discovery of double overcharging phenomena using HNC/MSA integral equations.

Findings

Overcharging occurs due to ionic correlations outside the nanopore.

Charge reversal is observed inside the nanopore.

Double overcharging is a newly identified phenomenon.

Abstract

Using the hypernetted-chain/mean spherical approximation (HNC/MSA) integral equations we study the electrical double layer inside and outside a model charged cylindrical vesicle (nanopore) immersed into a primitive model macroions solution, so that the macroions are only present outside the nanopore, i.e., the vesicle wall is impermeable only to the external macroions. We calculate the ionic and local linear charge density profiles inside and outside the vesicle, and find that the correlation between the inside and outside ionic distributions causes the phenomena of overcharging (also referred to as surface charge amplification) and/or charge reversal. This is the first time overcharging is predicted in an electrical double layer of cylindrical geometry. We also report the new phenomenon of double overcharging. The present results can be of consequence for relevant systems in physical-chemistry, energy storage and biology, e.g., nanofilters, capacitors and cell membranes.