Chemically synthesized gold nanoparticles embedded in a SiO2 matrix: A model system to give insights into nucleation and growth under irradiation

The control over the size and the dispersion of the ion beam-synthesized nanoparticles is generally poor. This is partially due to the scarce knowledge of the behavior of the precipitate phase in the first stages of the nucleation and growth processes. To overcome this difficulty, we explore the formation and growth under MeV ion irradiation of satellites clusters around chemically synthesized Au particles embedded in a silica matrix. Our results show that the satellites evolve in an Ostwald ripening regime limited by the diffusion in an open system. In addition, the complete evolution of the gold supersaturation is obtained and the temporal window for the nucleation regime is determined. It allows us to give a guideline method to improve the control of the particles monodispersity during the ion beam synthesis. Moreover, an estimation of the threshold concentration for nucleation, an effective value for the surface tension of the Au nanoparticles and the gold diffusivity under irradiation are given.