In situ TEM observation of liquid-state Sn nanoparticles vanishing in SiO2 structure: a potential synthetic tool for controllable morphologies 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 SnO2@SiO2 hollow nanostructures, for the first time, by interaction between liquid state Sn cores and SiO2 shell structures inside Sn@SiO2 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@SiO2 to yolk–shell Sn@SiO2 and hollow SnO2@SiO2 is demonstrated, showing the controllable structure of core–shell Sn@SiO2 nanoparticles via fixing liquid-state Sn inside a SiO2 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.