Monitoring the rapid nanocrystal transformation via trapped intermediates of silica encapsulation

In transmission electron microscopy (TEM), encapsulation is an important tool to preserve the nanoparticles from aggregation, weathering, and destructive high-energy electron beam. Traditionally, encapsulation can only be used to trap end products. This study pushes the limit of in situ encapsulation so that intermediates of short time scale can be trapped. Nanocrystals of water-soluble salts were generated from a solute-induced phase separation (SIPS) process. By performing a modified Stöber encapsulation on different time points of the process, a series of intermediates can be trapped by silica shells. By arranging and comparing the intermediates, it is possible to reconstruct the growing process of those water-soluble salt nanocrystals. Moreover, an example of the transition from nanocrystal to liquid droplet was discovered, unveiling a potentially alternative route of the SIPS process. The reported technique could capture more snapshots for TEM imaging, providing crucial information on the study of nanoscale growth mechanism.