Thermal annealing and laser-induced mechanisms in controlling the size and size-distribution of silver nanoparticles in Ag+-Na+ ion-exchanged silicate glasses

Abstract

Controlled precipitation of metal nanostructures into glassy matrices have demonstrated to be a valid way to synthesize materials suitable for photonics, optoelectronics and telecom purposes. However, the development of strategies for driving nanostructure formation, and then for tailoring the optical response of the metal doped systems, is still a challenge. Aiming at this, the present study focuses on silver state modification including nucleation/growth of Ag nanoparticles (NPs), manipulation of Ag NPs size and size-distribution in Ag+-Na+ ion exchanged silicate glasses undergone post-exchange treatments, such as thermal annealing and laser irradiation with different irradiation parameters. Raman and optical absorption spectroscopy analyses allow to follow the evolution of the Ag NPs precipitation process starting from the early stages of the overall mechanism, where the glassy matrix is permeated by a dense distribution of Ag0, Ag+ and small aggregates, which are the seeds for the formation of the larger particles upon energetic treatments. In these regards, it is observed that a proper choice of laser irradiation conditions, in terms of wavelength and pulse energy, has a direct impact on the occurrence of the overall clustering process, by specifically promoting Ag ion reduction as well as cluster nucleation, growth and fragmentation. This definitely paves the way to efficient strategies for the realization of optical materials based on controlled distribution of metal clusters with finely tuned structural and optical properties.