In Situ Electron Microscopy of Transformations of Copper Nanoparticles under Plasmonic Excitation

Metal nanoparticles are attractinginterest for their light-absorptionproperties, but such materials are known to dynamically evolve underthe action of chemical and physical perturbations, resulting in changesin their structure and composition. Using a transmission electronmicroscope equipped for optical excitation of the specimen, the structuralevolution of Cu-based nanoparticles under simultaneous electron beamirradiation and plasmonic excitation was investigated with high spatiotemporalresolution. These nanoparticles initially have a Cu core-Cu2O oxide shell structure, but over the course of imaging, theyundergo hollowing via the nanoscale Kirkendall effect. We capturedthe nucleation of a void within the core, which then rapidly growsalong specific crystallographic directions until the core is hollowedout. Hollowing is triggered by electron-beam irradiation; plasmonicexcitation enhances the kinetics of the transformation likely by theeffect of photothermal heating.