Confined diffusion of erbium excitations in SnO2 nanoparticles embedded in silica: A time-resolved infrared luminescence study

We have identified, in erbium-doped silica with SnO2 nanocrystals, excitation-diffusion processes restricted to the single nanocrystal. Time-resolved measurements of erbium infrared luminescence excited by energy transfer via nanocrystal excitation, together with the identification and quantification of the nanophase-related Er3+ variety by its electron paramagnetic resonance, have allowed us to analyze the dependence of the excitation decay rate on the number of ions per nanoparticle and to reveal the effects of the discrete spatial domain composed by nanocrystals. Finally, a nonlinear relation is derived to describe the effects of Förster energy transfer in disconnected nanosystems.