Partial Clustering in Binary Two-Dimensional Colloidal Suspensions

TL;DR

This study investigates partial clustering phenomena in binary colloidal suspensions at a water-air interface, revealing a general behavior of strongly coupled, negatively non-additive mixtures through theory, simulation, and experiments.

Contribution

It demonstrates the occurrence of partial clustering in binary colloidal mixtures, combining theoretical, computational, and experimental approaches to reveal a new structural phenomenon.

Findings

Partial clustering occurs in equilibrium in binary colloidal suspensions.

Small particles form sponge-like subclusters within voids of larger particles.

A characteristic small-wave vector peak appears in the structure factor.

Abstract

Strongly interacting binary mixtures of superparamagnetic colloidal particles confined to a two-dimensional water-air interface are examined by theory, computer simulation and experiment. The mixture exhibits a partial clustering in equilibrium: in the voids of the matrix of unclustered big particles, the small particles form subclusters with a sponge-like topology which is accompanied by a characteristic small-wave vector peak in the small-small structure factor. This partial clustering is a general phenomenon occurring for strongly coupled negatively non-additive mixtures.