O2 Diffusion in Amorphous SiO2 Nanoparticles Probed by Outgassing

An experimental study of the O-2 diffusion process in nanoparticles of amorphous SiO2 in the temperature range from 98 to 157 degrees C was carried out by Raman and photoluminescence techniques. We studied O-2 diffusion in high purity silica nanoparticles with a mean diameter of 14, 20, and 40 nm detecting the outgassing of molecules trapped during the manufacturing. The kinetics of diffusion is well described for all the investigated nanoparticles by the Fick's equation proving its applicability to nanoscale systems. The diffusion coefficient features an Arrhenius law temperature dependence in the explored temperature range, and the diffusion coefficient values are in good agreement with extrapolation of Arrhenius law from higher temperature studies.