Electrostatic interaction between dissimilar colloids at fluid interfaces

TL;DR

This study analytically investigates the electrostatic interactions between dissimilar charged colloids at fluid interfaces, revealing complex behaviors that challenge superposition approximations and providing insights relevant for emulsion stabilization.

Contribution

The paper introduces an analytical solution for electrostatic interactions between non-identical colloids at fluid interfaces using linearized Poisson-Boltzmann theory, highlighting non-monotonic behaviors.

Findings

Interaction exhibits both monotonic and non-monotonic variations.

Superposition approximation often fails to capture the behavior.

Expressions for surface, line, and interfacial tensions are derived.

Abstract

The electrostatic interaction between two non-identical, moderately charged colloids situated in close proximity of each other at a fluid interface is studied. By resorting to a well-justified model system, this problem is analytically solved within the framework of linearized Poisson-Boltzmann (PB) density functional theory (DFT). The resulting interaction comprises a surface and a line part, both of which, as functions of the inter-particle separation, show a rich behavior including monotonic as well as non-monotonic variations. In almost all cases, these variations cannot be captured correctly by using the superposition approximation. Moreover, expressions for the surface tensions, the line tensions and the fluid-fluid interfacial tension, which are all independent of the inter-particle separation, are obtained. Our results are expected to be particularly useful for emulsions stabilized by oppositely charged particles.