Fabrication and photoluminescence properties of core-shell structured spherical SiO 2 @Gd 2 Ti 2 O 7 :Eu 3+ phosphors
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n Yu and Rongshun Wanga) Department of Chemistry, Northeast Normal University, Changchun 130024, People’s Republic of China
Zhenling Wang, Zewei Quan, and Jun Linb) Key Laboratory of Rare Earth Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People’s Republic of China (Received 26 November 2005; accepted 9 March 2006)
A sol-gel technique was used to prepare Gd2Ti2O7:Eu3+-coated submicron silica spheres (SiO2@Gd2Ti2O7:Eu3+). The resulted SiO2@Gd2Ti2O7:Eu3+ core-shell particles were characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive x-ray spectra (EDS), transmission electron microscopy (TEM), photoluminescence (PL) spectra, as well as kinetic decays. The XRD results demonstrate that the Gd2Ti2O7:Eu3+ layers begin to crystallize on the SiO2 spheres after annealing at 800 °C and the crystallinity increases with raising the annealing temperature. The obtained core-shell phosphors have perfect spherical shape with narrow size distribution (average size ∼620 nm), non-agglomeration, and smooth surface. The thickness of the Gd2Ti2O7:Eu3+ shells on the SiO2 cores could be easily tailored by varying the number of deposition cycles (60 nm for four deposition cycles). Under the irradiation of 310 nm ultraviolet, the SiO2@Gd2Ti2O7:Eu3+ samples show strong emission of Eu3+. For the samples annealed from 600 to 800 °C, the emission is dominated by 613 nm red emission ascribed to 5D0–7F2 transition of Eu3+, while for those annealed from 900 to 1000 °C, the emission is dominated by 588 nm orange emission due to 5D0–7F1 transition of Eu3+. The PL intensity of Eu3+ increases with increasing the annealing temperature and the number of coating cycles. I. INTRODUCTION
The study of core-shell particles has generated much interest in recent years due to their fantastic properties different from those of single-component materials, and their synthesis has opened new directions for material research.1,2 Coating the particles with a thin shell of a compatible material makes it possible to control the interparticle and particle-matrix interactions, thereby further improving functional properties and expanding a broader range of potential application. The structure, size, and composition of these particles can be easily altered in a controllable way to tailor their magnetic, mechanical, thermal, electrical, electro-optical, and catalytic properties.3–6 In addition, the cost of materials can Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/JMR.2006.0297 2232 J. Mater. Res., Vol. 21, No. 9, Sep 2006 http://journals.cambridge.org Downloaded: 23 Aug 2014
be lowered by coating inexpensive cores with the expensive shell materials.7 Core-shell materials can also be used to act as fluorescent diagnostic labels,8 avoid photodegradation,9 enhance photoluminescence,10 create photonic crystals,11,12 and obtain novel optical effects
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