Role of Ceria Nanocrystals on Morphology and Luminescence of Eu3+ doped SiO2 nanopowder

Ceria nanocrystals embedded in Eu3+ doped in silica were prepared by sol-gel method. The evolution of cubic fluorite structure of ceria (CeO2) nanocrystal has been occurred in prepared nanopowder at a relatively low temperature (similar to 300 degrees C). Effect of annealing and role of CeO2 nanocrystals were further confirmed by XRD, FTIR and the elemental compositions were examined by SEM-EDS. It has been observed that the average size of nanocrystallites and their morphology would be tailored by varying the annealing temperature and CeO2 content. The incorporation of Eu3+ ions and CeO2 nanocrystal in silica were revealed by intense PL excitation and emission spectra. We have shown the efficient excitation process of Eu3+ ions through CeO2 nanocrystal in the material. The characteristic emission due to Eu3+ ions has been observed by all direct and indirect excitation wavelengths. It is observed that PL intensity at lambda(ex) = 325 nm has been increased tremendously by heat treatment due to removal of hydroxyl groups and remains almost same at lambda(ex) = 394 nm. The MD transition (D-5(0)-F-7(1)) dominated in as prepared sample by indirect excitation while ED transition (D-5(0)-F-7(2)) was pronounced in annealed samples after the formation of CeO2 nanocrystals. Impressively, enhancement in PL intensity via indirect excitation has been demonstrated via a schematic diagram of energy transfer mechanism from CeO2 nanocrystals to the Eu3+ ions.