Precisely shaping the structure of semiconductor inorganic nanocrystal building blocks is crucial for realizing their full potential in applications such as solar concentrators, quantum dot displays and biological imaging. Etching and growth processes have been harnessed to fabricate delicate structures from bulk semiconductors, yet we are still exploring the transformation principles of tiny colloidal nanostructures. To provide mechanistic insights, we seek to directly WATCH the reaction trajectories of individual nanocrystals in the native reaction environment using liquid cell transmission electron microscopy (LCTEM). The ultrathin liquid pocket containing the nanocrystals is encapsulated between two thin carbon layers, allowing the imaging electron beam to pass through without significant losses. I have recently succeeded in extending this technique to capture the elusive etching trajectories of semiconductor nanocrystals with lower imaging contrast. PbSe and CdSe are prototypical groups IV-VI and II-VI semiconductors, respectively. The microscopic trajectories observed here confirm that the etching mechanism of PbSe and CdSe nanocrystals under selective conditions are governed by the reactivity and surface energies of specific crystal facets.

Speaker

A/Prof. Chang Yan

School of Chemistry and Chemical Engineering, SJTU

Time

 2025.10.29 12:00-13:30