SiO₂:Tb³⁺@Lu₂O₃:Eu³⁺ Core–Shell Phosphors: Interfacial Energy Transfer for Enhanced Multicolor Luminescence

Abstract

Uniform and well-dispersed SiO₂:<i>x</i>%Tb³⁺@Lu₂O₃:<i>y</i>%Eu³⁺ core-shell spherical phosphors were synthesized via a solvothermal method followed by a subsequent calcination process. The structure, phase composition, and morphology of the samples were studied by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed that the Lu₂O₃:Eu³⁺ layer was evenly coated on the surface of SiO₂:Tb³⁺ spheres and the shell thickness was about 45-65 nm. The PL spectra and fluorescence lifetimes of the samples were further studied. It was proved that the multicolor luminescence of the samples could be realized by changing the doping concentration ratio of Eu³⁺ or by changing the excitation wavelengths. Compared with SiO₂@Lu₂O₃:3%Tb³⁺,6%Eu³⁺, SiO₂:3%Tb³⁺@Lu₂O₃:6%Eu³⁺ showed stronger luminescence intensity, longer fluorescence lifetime, and higher energy transfer efficiency, which was attributed to the effective interfacial energy transfer, and the interfacial energy transfer mechanism from Tb³⁺ to Eu³⁺ was a dipole-dipole interaction mechanism. The XPS results indicated that the sample contained a high content of Si-O-Lu bonds, which proved that there was a strong interaction between the SiO₂ core and the Lu₂O₃ shell, making the interfacial energy transfer possible. These results provided a new idea for luminescence enhancement and multicolor luminescence.