Three-dimensional Binary Superlattices of Oppositely-charged Colloids

TL;DR

This paper demonstrates the controlled self-assembly of binary colloidal crystals with tunable structures by adjusting charge, revealing the competition between entropic and Coulombic forces in determining crystal arrangements.

Contribution

It introduces a method to switch between different binary crystal structures of colloids by varying charge, advancing understanding of colloidal self-assembly.

Findings

Binary crystal structures can be switched by charge variation.

Face-centered cubic, cesium chloride, and sodium chloride structures observed.

Structural transformations explained by entropic and Coulombic interactions.

Abstract

We report the equilibrium self-assembly of binary crystals of oppositely-charged colloidal microspheres at high density. By varying the magnitude of the charge on near equal-sized spheres we show that the structure of the binary crystal may be switched between face-centered cubic, cesium chloride and sodium chloride. We interpret these transformations in terms of a competition between entropic and Coulombic forces.