Advances of Nonclassical Crystallization toward Self-Purification of Precious Metal Nanoparticle Mixtures

Abstract

Crystallization is a common procedure used for the purification of compounds. In this work, we use particle-mediated crystallization (i.e., “nonclassical crystallization”) to separate mixtures of core–shell (Au@Ag) nanocrystals of different size and shape into “ordered” phases (i.e., crystalline domains) with nanocrystals of similar morphology and size. The self-assembly process of the drying “coffee ring” effect and of depletion forces and the resulting superstructures are investigated. A “depletion” based technique efficiently separates nanoparticle mixtures with small differences in size (12–22%) within isolated colloidal crystals, while the “coffee ring” technique works better for nanoparticles with a bigger difference in size and shape. Besides the development of a successful approach for the self-purification of nanoparticle mixtures, this study additionally deepens our understanding on particle mediated crystallization under various conditions.