| Abstract
| - Spherical SiO2 particles have been successfully coated with YVO4:Eu3+ phosphor layers through aPechini sol−gel process. The resulted YVO4:Eu3+@SiO2 core−shell phosphors were characterized byX-ray diffraction (XRD), Fourier-transform IR spectroscopy, scanning electron microscopy, X-rayphotoelectron spectra, transmission electron microscopy, UV/vis absorption spectra, general and time-resolved photoluminescence spectra, as well as kinetic decays. The XRD results demonstrate that theYVO4:Eu3+ layers begin to crystallize on the SiO2 particles after annealing at 400 °C, and the crystallinityincreases with raising the annealing temperature. The obtained core−shell phosphors have perfect sphericalshape with narrow size distribution (average size ca. 500 nm), nonagglomeration, and smooth surface.The thickness of the YVO4:Eu3+ shells on SiO2 cores could be easily tailored by varying the number ofdeposition cycles (60 nm for two deposition cycles). The Eu3+ shows a strong photoluminescence (PL)(dominated by 5D0−7F2 red emission at 617 nm) due to an efficient energy transfer from vanadate groupsto Eu3+. The energy transfer process was further studied by the time-resolved emission spectra as wellas kinetic decay curves of Eu3+ upon excitation into the VO43- ion. The PL intensity of Eu3+ increaseswith raising the annealing temperature and the number of coating cycles, and optimum polyethyleneglycol concentration in the precursor solution was determined to be 0.08 g/mL for obtaining the strongestemission of Eu3+.
- An effective and simple sol−gel process has been developed to deposit YVO4:Eu3+ layers on SiO2 spheres. The obtained YVO4:Eu3+@SiO2 core−shell phosphors have spherical morphology, sub-micrometer size, and narrow size distribution. The photoluminescence intensity of the core−shell phosphors can be tuned by the annealing temperature and the number of coatings, etc.
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