In situ TEM observation of liquid-state Sn nanoparticles vanishing in a SiO 2 structure: a potential synthetic tool for controllable morphology evolution from core-shell to yolk-shell and hollow structures.

Precise design of hollow nanostructures can be realized via various approaches developed in the last two decades, endowing nanomaterials with unique structures and outstanding performances, showing their usefulness in a broad range of fields. Herein, we demonstrate the formation of SnO 2 @SiO 2 hollow nanostructures, for the first time, by interaction between liquid state Sn cores and SiO 2 shell structures inside Sn@SiO 2 core-shell nanoparticles with real-time observation via in situ transmission electron microscopy (TEM). Based on the in situ results, designed transformation of the nanoparticle structure from core-shell Sn@SiO 2 to yolk-shell Sn@SiO 2 and hollow SnO 2 @SiO 2 is demonstrated, showing the controllable structure of core-shell Sn@SiO 2 nanoparticles via fixing liquid-state Sn inside a SiO 2 shell which has a certain Sn containing capacity. The present approach expands the toolbox for the design and preparation of yolk-shell and hollow nanostructures, thus providing us with a new strategy for fabrication of more complicated nanostructures.