A facile one-pot hydrothermal method to prepare europium-doped titania hollow phosphors and their sensitized luminescence properties

Monodisperse europium-activated titania hollow phosphors had been synthesized by a facile one-pot hydrothermal method using carbon spheres as hard templates. Samples were characterized by X-ray powder diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, energy dispersive spectrometer and photoluminescence spectrum. The strongest emission intensity was observed with TiO2:Eu-0.2 hollow spheres and TiO2: Eu-0.2 hollow spheres calcining at 550 degrees C. Moreover, the strongest excitation of TiO2:Eu-0.2 hollow spheres transferred from 400 to 500 degrees C and the effective nonradiative energy transfer from the TiO2 hollow spheres host matrix to Eu3+ ions crystal field states was realized due to changes of crystalline field in the environment around Eu3+ ions occupying Ti4+ sites. The proposed energy transfer mechanism was that UV light is absorbed in the band of TiO2 hollow spheres crystal and then the energy is relaxed to the defect states of TiO2 host. The energy can transfer to the crystal states of Eu3+ ions (F-7(j), j = 0, 1, 2, 3 and 4), which results in efficient photoluminescence. The fluorescent intensity of TiO2:Eu-0.2 hollow spheres was 2.2 times as strong as that of TiO2:Eu-0.2 bulk material. Crown Copyright (c) 2010 Published by Elsevier B.V. All rights reserved.