Soft Matter. 2016 Jun 21;12(23):5199-204. doi: 10.1039/c6sm00620e. Epub 2016 May 19.

Using depletion to control colloidal crystal assemblies of hard cuboctahedra.

Soft matter

Andrew S Karas, Jens Glaser, Sharon C Glotzer

PMID: 27194463 DOI: 10.1039/c6sm00620e

Abstract

Depletion interactions arise from entropic forces, and their ability to induce aggregation and even ordering of colloidal particles through self-assembly is well established, especially for spherical colloids. We vary the size and concentration of penetrable hard sphere depletants in a system of cuboctahedra, and we show how depletion changes the preferential facet alignment of the colloids and thereby selects different crystal structures. Moreover, we explain the cuboctahedra phase behavior using perturbative free energy calculations. We find that cuboctahedra can form a stable simple cubic phase, and, remarkably, that the stability of this phase can be rationalized only by considering the effects of both the colloid and depletant entropy. We corroborate our results by analyzing how the depletant concentration and size affect the emergent directional entropic forces and hence the effective particle shape. We propose the use of depletants as a means of easily changing the effective shape of self-assembling anisotropic colloids.

Publication Types

• Journal Article