On the nature of long-range contributions to pair interactions between charged colloids in two dimensions

TL;DR

This study analyzes the effective pair interactions in highly charged 2D colloids, revealing that long-range attractions can appear but are limited by particle spacing, and purely repulsive potentials can explain observed distributions.

Contribution

It provides a detailed inverse analysis of experimental data, showing the conditions under which long-range attractions occur and are limited in charged colloids.

Findings

Long-range attractive potentials are observed at high densities.

Stable solutions are limited by nearest neighbor distances.

Purely repulsive potentials can explain the measured distributions.

Abstract

We perform a detailed analysis of solutions of the inverse problem applied to experimentally measured two-dimensional radial distribution functions for highly charged latex dispersions. The experiments are carried out at high colloidal densities and under low-salt conditions. At the highest studied densities, the extracted effective pair potentials contain long-range attractive part. At the same time, we find that for the best distribution functions available the range of stability of the solutions is limited by the nearest neighbour distance between the colloidal particles. Moreover, the measured pair distribution functions can be explained by purely repulsive pair potentials contained in the stable part of the solution.