Multistep nucleation of nanocrystals in aqueous solution

N. Duane Loh, Soumyo Sen, Michel Bosman, Shu Fen Tan, Jun Zhong, Christian A. Nijhuis, Petr Král, Paul Matsudaira & Utkur Mirsaidov

Nature Chemistry 9, 77–82 (2017) doi:10.1038/nchem.2618
Received 08 May 2016 Accepted 18 August 2016 Published online 03 October 2016

The nucleation and growth of solids from solutions impacts many natural processes and is fundamental to applications in materials engineering and medicine. For a crystalline solid, the nucleus is a nanoscale cluster of ordered atoms that forms through mechanisms still poorly understood. In particular, it is unclear whether a nucleus forms spontaneously from solution via a single- or multiple-step process. Here, using in situ electron microscopy, we show how gold and silver nanocrystals nucleate from supersaturated aqueous solutions in three distinct steps: spinodal decomposition into solute-rich and solute-poor liquid phases, nucleation of amorphous nanoclusters within the metal-rich liquid phase, followed by crystallization of these amorphous clusters. Our ab initio calculations on gold nucleation suggest that these steps might be associated with strong gold–gold atom coupling and water-mediated metastable gold complexes. The understanding of intermediate steps in nuclei formation has important implications for the formation and growth of both crystalline and amorphous materials.

Read online: Nature Chemistry.