Ge Nanocages and Nanoparticles via Microwave-Assisted Galvanic Replacement for Energy Storage Applications

We report a systematic study on the synthesis of highly monodisperse hollow germanium (Ge) nanoparticles (NPs) via galvanic replacement reactions between GeI2 and Ag NPs. By fine-tuning the synthetic parameters such as temperature, precursor molar ratio, ligand concentration, and so forth, the morphology and surface structure of the Ge NPs can be precisely controlled. We also report a method to synthesize solid Ge NPs and Ag@Ge core–shell metal–semiconductor NPs with a controllable uniform shell thickness. An inward diffusion mechanism for galvanic replacement is proposed and supported by imaging the different stages of the reaction and analysis of the products. This mechanism allows the reaction to be self-terminated and achieves nanometer-sized accuracy. The galvanic reaction may be applied to other semiconductors and could serve as a powerful alternative to the classical nucleation-growth mechanism and subsequently advance the scale-up and further energy storage applications.