Image charges in spherical geometry: Application to colloidal systems

TL;DR

This paper investigates the influence of image charges in spherical geometries on colloidal systems through analytical solutions and Monte Carlo simulations, revealing consistent counterion density maxima across various conditions.

Contribution

It provides an exact analytical study of a microion near a dielectric sphere and extensive simulation results on how image charges affect electrical double layers in colloids.

Findings

Counterion density maxima are consistent across different valences and salt conditions.

Image charges significantly influence the structure of electrical double layers.

The position of counterion density peaks remains similar to single-counterion cases.

Abstract

The effects of image charges (i.e., induced surface charges of polarization) in spherical geometry and their implication for charged colloidal systems are investigated. We study analytically and exactly a single microion interacting with a dielectric sphere and discuss the similarities and discrepancies with the case of a planar interface. By means of extensive Monte Carlo (MC) simulations, we study within the framework of the primitive model the effects of image charges on the structure of the electrical double layer. Salt-free environment as well as salty solutions are considered. A remarkable finding of this study is that the position of the maximum in the counterion density (appearing at moderately surface charge density) remains quasi-identical, regardless of the counterion valence and the salt content, to that obtained within the \textit{single}-counterion system.