Size-dependent luminescence of Sm³⁺ doped SnO₂ nano-particles dispersed in sol-gel silica glass

Abstract

Sol-gel glasses with composition (100−x)SiO₂–xSnO₂ doped with 0.4 mol% of Sm³⁺, with x ranging from 1 to 10, have been successfully synthesized. Transparent doped nano-glass-ceramics were prepared by thermal treatment of the precursor glasses at 900°C during 4 hours, leading to nanocomposites comprising SnO₂ nanocrystals embedded into an amorphous SiO₂ phase. A structural analysis in terms of X-ray Diffraction and High Resolution Transmission Electron Microscopy confirms the precipitation of SnO₂ nanocrystals within the glassy matrix. The mean radius of the obtained SnO₂ nanocrystals, ranging from 2.1 to 4.7 nm calculated by the Scherrer and Brus equations, similar to the Bohr’s exciton radius, constitutes a wide band-gap semiconductor quantum-dot system. Energy transfer from SnO₂ nanocrystal host to Sm³⁺ ions is confirmed by luminescence spectra and analyzed as a function of SnO₂ concentration, showing an evolution that could be ascribed to selective excitation of nanocrystal sets with predetermined size. Besides, a study of the luminescence as a function of temperature helps to clarify the involved energy transfer mechanisms.