Multicolor tunable luminescence and energy transfer of core–shell structured SiO2@Gd2O3 microspheres co-activated with Dy3+/Eu3+ under single UV excitation

Abstract

Optimizing structure and varying doped ions are two main strategies to obtain excellent luminescence performance. Spherical morphology is considered to be the most ideal phosphor structure due to the least surface defects. Herein, a series of spherical and monodispersed Dy³⁺/Eu³⁺ co-activated SiO₂@Gd₂O₃ core–shell phosphors with multicolor tunable luminescence were successfully prepared via a facile urea assisted precipitation method. Related chemical reactions and the possible growth mechanism of Gd₂O₃:Ln³⁺ directional deposition on the surface of SiO₂ microspheres were put forward. Upon 273 nm UV radiation excitation, SiO₂@Gd₂O₃:Dy³⁺ and SiO₂@Gd₂O₃:Eu³⁺ samples exhibited characteristic yellow (⁴F_9/2–⁶H_13/2) and blue (⁴F_9/2–⁶H_15/2) emissions of Dy³⁺ and red (⁵D₀–⁷F₂) emission of Eu³⁺, respectively. Meanwhile, multicolor emissions (warm white, yellow and orange) could be easily obtained by modulating the relative content of Dy³⁺ and Eu³⁺ in SiO₂@Gd₂O₃:Ln³⁺ samples under a single excitation wavelength. Moreover, it was confirmed that Dy³⁺ could transfer energy to Eu³⁺ in the form of quadrupole–quadrupole interaction and further improved the luminescence intensity of Eu³⁺ by comparing experimental data with theoretical calculations. These results imply that tunable luminescence Dy³⁺,Eu³⁺ co-doped SiO₂@Gd₂O₃ microspheres have great potential applications in multicolor displays and biolabeling fields.