Insights into Initial Kinetic Nucleation of Gold Nanocrystals

摘要

Abstract: Understanding the initial nucleation mechanism of monodisperse nanocrystals (NCs) duringnsynthesis process is an important prerequisite to control the desired sizes and to manipulate the propertiesnof nanoscale materials. The acquisition of information for the small nanocluster nucleation process, however,nstill remains challenging. Here, using a continuous-flow in situ X-ray absorption fine structure (XAFS)nspectroscopy for time-resolved studies, we have clarified the initial kinetic nucleation of Au clusters undernthe grain size of 1 nm for the classical Au NCs synthesis via the reduction of AuCl4 in aqueous solution.nThe in situ XAFS results present the experimental revelation of the formation of intermediate Cl3 Au AuCl3ndimer and the subsequent higher complexes ‘AunCln x’ in the initial nucleation stage. We propose a kineticnthree-step mechanism involving the initial nucleation, slow growth, and eventual coalescence for the AunNCs formation, which may be helpful for the synthesis of metallic nanomaterials.