The Effects of Asymmetric Salt and a Cylindrical Macroion on Charge Inversion: Electrophoresis by Molecular Dynamics Simulations

TL;DR

This study uses molecular dynamics simulations to explore how asymmetric salts and macroion shape influence charge inversion, revealing key dependencies on ion size, valence, and macroion geometry.

Contribution

It provides new insights into the effects of asymmetric salt properties and macroion shape on charge inversion phenomena through detailed simulation analysis.

Findings

Reversed electrophoretic mobility increases with coion to counterion radius ratio.

Charge inversion is enhanced by monovalent salt at low ionic strength.

Cylindrical macroions are more resistant to salt effects than spherical ones.

Abstract

The charge inversion phenomenon is studied by molecular dynamics simulations, focusing on size and valence asymmetric salts, and a threshold of surface charge density for charge inversion. The charge inversion criteria by the electrophoretic mobility and the radial distribution functions of ions coincide except around the charge inversion threshold. The reversed electrophoretic mobility increases with the ratio of coion to counterion radii, while it decreases with the ratio of coion to counterion valences. The monovalent salt enhances charge inversion of a strongly charged macroion at small ionic strength, but it reduces reversed mobility otherwise. A cylindrical macroion is more persistent to monovalent salt than a spherical macroion of the same radius and surface charge density.