Stokes and Anti-Stokes Luminescent Rare-Earth-Doped Tantalum Oxide Nanoparticles

Doping of nano- and microparticles of oxides with rareearth elements(REEs) is used to fine-tune their structural, optical, and electrochemicalproperties. On the way to establish the structure-propertyrelationship, we dope tantalum oxide (Ta2O5)particles with REEs to study their effect on the oxide structure andluminescence. Ta2O5 is highly perspective inmedicine, catalysis, and optics, but its crystal structure is insufficientlystudied. Two synthesis approaches (sol-gel and solvothermal)were used to obtain powders with different textures. Experimentaland theoretical studies of amorphous and crystallized tantalum oxideNPs by means of X-ray powder diffraction, Rietveld analysis, EXAFS/XANESspectroscopy, and density functional theory calculations were performed.All samples (doped and undoped) crystallized in orthorhombic phasewith no admixtures. It was demonstrated that Ta2O5 is a promising wide-spectrum luminescent material: by combiningREEs, both Stokes and anti-Stokes luminescence in the visible regionwere obtained. By means of optical absorption spectroscopy, it wasshown that the prepared samples could be classified as wide band gapsemiconductors. Onthe way to establish the structure-property relationship,tantalum oxide (Ta2O5) particles were dopedwith REE to study their effect on the oxide structure and luminescence.The experimental and theoretical studies of amorphous and crystallizedtantalum oxide NPs by means of X-ray powder diffraction, Rietveldanalysis, EXAFS/XANES spectroscopy, and density functional theorycalculations were performed.