Nonclassical Recrystallization

Abstract

Applications in the fields of materials science and nanotechnology increasingly demand for monodisperse nanoparticles in size and shape. Up to now, no general purification procedure exists to thoroughly narrow the size and shape distributions of nanoparticles. Here, we show by analytical ultracentrifugation (AUC) as an absolute and quantitative high-resolution method that multiple recrystallization of nanocrystals to mesocrystals is a very efficient tool to generate nanocrystals with an excellent and so-far unsurpassed size-distribution (PDI = 1.0001) and shape. Similar to the crystallization of molecular building blocks, non-classical recrystallization removes "molecular" and "colloidal" impurities (i.e. nanoparticles, which are different in shape and size from the majority) by assembling them to a mesocrystal. In case of nanocrystals, this assembly can be size- and shape-selective, since mesocrystals show both long-range packing ordering and preferable crystallographic orientation of nanocrystals. Beside the generation of highly monodisperse nanoparticles, these findings provide highly relevant insights into crystallization of mesocrystals.