Electrostatic Interactions between Janus Particles

TL;DR

This study investigates the electrostatic interactions of Janus particles with asymmetric charge distributions, comparing simulation results with mean-field theories to evaluate the validity of DLVO-like models for such complex colloids.

Contribution

It introduces a method to compare Monte Carlo simulations with Poisson-Boltzmann theory and derives practical expressions for Janus-particle interactions, extending the understanding of their electrostatic behavior.

Findings

Poisson-Boltzmann approximation is valid within a specific parameter range.

DLVO-like theories accurately describe Janus-particle interactions within this range.

The techniques developed can be applied to other charged-patterned particles.

Abstract

In this paper we study the electrostatic properties of `Janus' spheres with unequal charge densities on both hemispheres. We introduce a method to compare primitive-model Monte Carlo simulations of the ionic double layer with predictions of (mean-field) nonlinear Poisson-Boltzmann theory. We also derive practical DLVO-like expressions that describe the Janus-particle pair interactions by mean-field theory. Using a large set of parameters, we are able to probe the range of validity of the Poisson-Boltzmann approximation, and thus of DLVO-like theories, for such particles. For homogeneously charged spheres this range corresponds well to the range that was predicted by field-theoretical studies of homogeneously charged flat surfaces. Moreover, we find similar ranges for colloids with a Janus-type charge distribution. The techniques and parameters we introduce show promise for future studies of an even wider class of charged-patterned particles.