Step by step resolving the formation of dendritic crystal in solution: an observation against the classical model of one-by-one addition

Abstract

During crystallization, one-by-one addition of atomic species or nucleation-generated nanoparticles is widely considered to be the fundamental mode to construct advanced morphologies. However, due to a lack of approaches with high resolution and real-time tracing ability, the correctness of this conventional concept has never been verified in a complicated crystallization process, even including the simplest species--the formation of dendritic crystals. In this work, we successfully resolved the growth mechanism of dendritic KCl crystals in a thin water film by terminating the continuous crystallization at different stages. The results were quite against the conventional concept. For example, one-by-one aggregation of individual ions was unable to directly form a dendritic morphology, and nucleation-generated nanoparticles had been prearranged into dendritic configuration before they could attach one another. In summary, the crystallization was precisely self-controlled to follow several specific steps rather than the simple addition of building blocks.