Unfolding diffusion-based Ag nanoparticle growth in SiO₂ nanofilms heat-treated in air via in situ optical microspectroscopy

In situ optical microspectroscopy has been demonstrated effective in resolving diffusion-based growth from oxidation processes for Ag nanoparticles (NPs) embedded in silica nanofilms during thermal processing in air atmosphere. The choice of an elevated heating rate for achieving the desired terminal temperatures at which optical properties are monitored allows for increasing the sensitivity of the technique for the elucidation of NP growth. Silver NPs have been indicated to grow via Ag diffusion in an early stage of thermal treatment up to 10 min in the 570-600 °C temperature range. The isothermal time variation in Ag NP size was monitored by fitting the experimentally obtained surface plasmon resonance profiles with spectra calculated by Mie theory. The spectroscopic data was then analyzed in the context of crystal growth theory. The analysis of the time-dependent isotherms has allowed for estimating the activation energy for the process at 3.2 eV.