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

摘要

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 TiO_2:Eu_(0.2) hollow spheres and TiO_2:Eu_(0.2) hollow spheres calcining at 550 ℃. Moreover, the strongest excitation of TiO_2:Eu_(0.2) hollow spheres transferred from 400 to 500 ℃ and the effective nonradiative energy transfer from the TiO2 hollow spheres host matrix to Eu~(3+) ions crystal field states was realized due to changes of crystalline field in the environment around Eu~(3+) ions occupying Ti~(4+) sites. The proposed energy transfer mechanism was that UV light is absorbed in the band of TiO_2 hollow spheres crystal and then the energy is relaxed to the defect states of TiO_2 host. The energy can transfer to the crystal states of Eu~(3+) ions (7F_j, j = 0, 1, 2, 3 and 4), which results in efficient photoluminescence. The fluorescent intensity of TiO_2:Eu_(0.2) hollow spheres was 2.2 times as strong as that of TiO2:Eu0.2 bulk material.