Attractions between charged colloids at water interfaces

TL;DR

This paper analyzes the effective potential between charged colloids at water interfaces, revealing the interplay of electrostatic repulsion and capillary attraction, with conditions for potential minima based on colloid charge and screening length.

Contribution

It provides a detailed analysis of the combined electrostatic and capillary interactions, highlighting conditions for attractive minima in colloid interactions at water interfaces.

Findings

Capillary attraction can dominate electrostatic repulsion at large distances for high charges.

The effective potential shows a minimum at intermediate separations under specific size and screening conditions.

Both electrostatic and capillary parts exhibit dipole-like asymptotic behavior.

Abstract

The effective potential between charged colloids trapped at water interfaces is analyzed. It consists of a repulsive electrostatic and an attractive capillary part which asymptotically both show dipole--like behavior. For sufficiently large colloid charges, the capillary attraction dominates at large separations. The total effective potential exhibits a minimum at intermediate separations if the Debye screening length of water and the colloid radius are of comparable size.