Luminescence Studies and Judd-Ofelt Analysis on SiO2@LaPO4:Eu@SiO2 Submicro-spheres with Different Size of Intermediate Shells

Xiaowei Zhu; Kuisuo Yang; Anping Wu; He Bai; Jinrong Bao; Yan Qiao; Yunjiang Yang; Wenxian Li; Ying Liu

doi:10.1038/s41598-019-49323-6

Luminescence Studies and Judd-Ofelt Analysis on SiO₂@LaPO₄:Eu@SiO₂ Submicro-spheres with Different Size of Intermediate Shells

Sci Rep. 2019 Sep 10;9(1):13065. doi: 10.1038/s41598-019-49323-6.

Authors

Xiaowei Zhu¹, Kuisuo Yang², Anping Wu², He Bai², Jinrong Bao³, Yan Qiao², Yunjiang Yang², Wenxian Li², Ying Liu²

Affiliations

¹ College of Pharmacology, Inner Mongolia Medical University, Hohhot, 010059, China.
² Inner Mongolia Key Laboratory of Chemistry and Physics of Rare Earth Materials, College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot, 010021, China.
³ Inner Mongolia Key Laboratory of Chemistry and Physics of Rare Earth Materials, College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot, 010021, China. jinrongbao@imu.edu.cn.

Abstract

The novel submicro-spheres SiO₂@LaPO₄:Eu@SiO₂ with core-shell-shell structures were prepared by connecting the SiO₂ submicro-spheres and the rare earth ions through an organosilane HOOCC₆H₄N(CONH(CH₂)₃Si(OCH₂CH₃)₃ (MABA-Si). The as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and infrared spectroscopy (IR). It is found that the intermediate shell of the submicro-spheres was composed by LaPO₄:Eu nanoparticles with the size of about 4, 5-7, or 15-34 nm. A possible formation mechanism for the SiO₂@LaPO₄:Eu@SiO₂ submicro-spheres has been proposed. The dependence of the photoluminescence intensity on the size of the LaPO₄:Eu nanoparticles has been investigated. The intensity ratios of electrical dipole transition ⁵D₀ → ⁷F₂ to magnetic dipole transition ⁵D₀ → ⁷F₁ of Eu³⁺ ions were increased with decreasing the size of LaPO₄:Eu nanoparticles. According to the Judd-Ofelt (J-O) theory, when the size of LaPO₄:Eu nanoparticles was about 4, 5-7 and 15-34 nm, the calculated J-O parameter Ω₂ (optical transition intensity parameter) was 2.30 × 10^-20, 1.80 × 10^-20 and 1.20 × 10^-20, respectively. The increase of Ω₂ indicates that the symmetry of Eu³⁺ in the LaPO₄ lattice was gradually reduced. The photoluminescence intensity of the SiO₂@LaPO₄:Eu@SiO₂ submicro-spheres was unquenched in aqueous solution even after 15 days.