The Effect of Size and Thermal Treatment on the Photoluminescent Properties of Europium-Doped SiO2 Nanoparticles Prepared in One Pot by Sol-Gel.

Europium (Eu)-doped silica nanoparticles have attracted great interest for different applications, in particular in biomedicine as biosensors or for tissue regeneration. Sol-gel is the most common process used to prepare those particles, with size varying from tens to hundreds of nanometers. In this article, we focus our attention on the comparison between two commonly used sol-gel derived methods: reverse microemulsion (for particles smaller than 100 nm) and Stöber method (for particles larger than 100 nm). Europium concentration was varied between 0.2 and 1 mol%, and the nanoparticle diameters were 10, 50 and 100 nm. The link between the local environment of europium ions and their optical properties was investigated and discussed. Using Transmission Electron Microscopy, nitrogen sorption, X-ray diffraction, Fourier-Transform Infra-Red and pulsed doubled Nd:YAG laser, we confirmed that fluorescence lifetime was improved by thermal treatment at 900 °C due to the elimination of aqueous environment and modification of structure disorder. The size of nanoparticles, the amount of europium and the thermal treatment of obtained materials influence the emission spectra and the decay curves of Eu3+.

Europium-Doped Sol-Gel SiO2-Based Glasses: Effect of the Europium Source and Content, Magnesium Addition and Thermal Treatment on Their Photoluminescence Properties.

Rare-earth doped silica-based glasses lead the optical materials due to their tailorable spectroscopic and optical properties. In this context, we took advantage of the sol-gel process to prepare various Eu-doped silica glasses to study their luminescent properties before and after annealing at 900 °C. The effect of magnesium on these properties was studied in comparison with Mg-free-glass. Using TEM, nitrogen sorption, XRD and FT-IR, we confirmed that the magnesium modifies the glass structure and the thermal treatment eliminates the aqueous environment, modifying the structure ordering. The emission spectra and the decay time curves show the advantages of the Mg addition and the annealing on the photoluminescent properties.

Effect of compositional variation on optical and structure properties of europium-doped SiO(2)-HfO(2) glasses.

Glasses with compositions (100-x)SiO(2)-xHfO(2):0.3Eu(3+) (molar ratio, x=0,10,20,30) for optical applications were prepared using the sol-gel route. The introduction of hafnium into the glass matrix induced the energy splitting of the F27 state of Eu(3+) ions. Furthermore, fluorescence line narrowing (FLN) spectra indicated that Eu(3+) clustering occurred in glasses containing no hafnium. The addition of hafnium promoted better dispersion of Eu(3+) ions in the glass matrix. The role of hafnium on modifying the properties of glasses was discussed with respect to x-ray diffraction and FLN analysis.