Monitoring the rapid nanocrystal transformation via trapped intermediates of silica encapsulation

Abstract

In transmission electron microscopy (TEM), encapsulation is an important tool to preserve the nanoparticles from aggregation, weathering, and destructive highenergy 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.

Liquid-on-solid heterogeneous nucleation for a general synthesis of yolk–shell nanostructures

“…Previously, we have shown that adding TEOS at the beginning could capture very early stage intermediates. 13 However, we failed to capture the “naked” AuNPs and “empty” syrup droplets (the nanoshells) before their collision (Fig. 3b), indicating that collision is only a minor pathway.…”