Synthesis, characterization and formation mechanism of alloy and metal oxide nanoparticles

Abstract

Metal nanoparticles can possess intriguing properties due to their nanoscale dimensions, and are intensively applied in research. With the development of synthetic systems, classic crystal growth theories become limited and cannot explain current conditions very well. The aim of this project is to find out the factors that influence crystal growth at the nanoscale and develop general methods to prepare shape-controlled nanomaterials. The growth process of CuPt nanorods is studied and a ligand mediated mechanism is proposed. It reveals that surface ligands are crucial in guiding the one dimensional growth through their mutual interactions. Solvent effect is discovered to be able to control the nanoparticles morphology, by indirectly tuning the interactions between ligands and the surface of a particle. Based on this mechanism, titanate nanosheets with a monolayer thickness are prepared with the assistance of surface ligands. An effective, one-step method is developed to prepare CuPd nanowire networks, which demonstrates its versatility in the preparation of other alloyed networks. The growth process of CuPt nanoparticles are investigated, and show that the growth pathway can be a reversed, surface-to-core crystallization route. The effect of dealloying, including acid etching and galvanic replacement, is studied and used to fabricate nanoparticles with various morphologies. The findings in this project highlight the influence of surface ligands in the synthesis of nanocrystals, provide new perspectives of crystal growth mechanisms and offer practical knowledge for nanostructuring materials.