Experimental study on the coalescence process of SiO2 supported colloidal Au nanoparticles

Abstract

We report on an experimental study of the coalescence-driven grow process of colloidal Au nanoparticles on SiO2 surface. Nanoparticles with 30, 50, 80, 100nm nominal diameters on a SiO2 substrate were deposited, from solutions, by the drop-casting method. Then, annealing processes, in the 573–1173K temperature range and 900–3600s time range, were performed. Using scanning electron microscopy analyses, the temporal evolution of the nanoparticles sizes has been studied. In particular, for all classes of nanoparticles, the experimental-obtained diameters distributions evidenced double-peak shapes (i. e. bimodal distributions): a first peak centered (and unchanged changing the annealing temperature and/or time) at the nominal diameter of the as-deposited nanoparticles, 〈D0〉, and a second peak shifting at higher mean diameters, 〈DC〉, increasing the annealing temperature and/or time. This observation suggested us a coalescence-driven growth process of a nanoparticles sub-population. As a consequence, the temporal evolution of 〈DC〉 (for each class of nanoparticles and each annealing temperature), within the well-established particles coalescence theoretical framework, has been analyzed. In particular, by the analyses of the experimental data using relations as prescribed by the theoretical model, a characteristic size-dependent activation energy for the Au nanoparticles coalescence process has been evaluated.