Phase separation in binary colloids with charge asymmetry

Abstract

We report that binary dispersions of like-charged colloidal particles with large charge asymmetry but similar size exhibit phase separation into crystal and fluid phases under very low salt conditions. This is unexpected because the effective colloid–colloid pair interactions are accurately described by a Yukawa model which is stable to demixing. We show that colloid–ion interactions provide an energetic driving force for phase separation, which is initiated by crystallization of one species.