Modelling the Growth and Aggregation of Gold Nanoparticles Using Liquid-Phase Transmission Electron Microscopy

The ability to synthesize nanoparticles of desired shape, size and composition relies heavily on our understanding on how to finely control various factors influencing the formation, such as the kinetics of growth. Fundamental study on the nucleation and growth of nanoparticles found itself at the forefront with the application of liquid-phase transmission electron microscopy (LTEM) in the investigation of dynamic growth and assembly processes. Since early study using LTEM to observe and quantify the nucleation and growth of single colloidal platinum nanoparticles, several theoretical models have been developed. More complex mode of formation was also revealed based on a hybrid growth process of gold on platinum icosahedral nanoparticles to form core-shell structures. These studies have been carried out by focusing on single or a small number of nanoparticles. Herewith, we present a study on the establishment of an analytical method to quantify the particle formation using in situ LTEM technique. This approach is based on the analysis of median particle size and focused on main events accounted for the formation of nanoparticles at a given time. We found that unlike the cases for single particle analysis, the observed formation rate could not be explained by any single formation mode, such as diffusion- and/or reaction-controlled growth described by the Liftshitz-Slyosov-Wagner theory or formation through coalescence as described by the Smoluchowski aggregative kinetics. A global fit was used to describe the entire formation of nanoparticles in an ensemble.