RESUMO
Uniform and well-dispersed SiO2:x%Tb3+@Lu2O3:y%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.
