SiO2@TiO2:Eu3+ and Its Derivatives: Design, Synthesis, and Properties

SiO2@TiO2:Eu3+ core–shell structure was synthesized by a surfactant-free solvothermal method, and its luminescence intensities were increased through a coating SiO2 layer. Furthermore, SiO2@TiO2:Eu3+@SiO2 core double-shell structures with different coating thicknesses have been prepared to examine the relationship between luminescence intensity and thickness. In addition, luminescence enhancement mechanisms including the surface repair effect and excitation/emitted light absorption effect were proposed. Moreover, the luminescence properties and photocatalytic behaviors of SiO2@TiO2:Eu3+ core–shell structure and its derivatives SiO2@TiO2:Eu3+ yolk–shell structure and TiO2:Eu3+ hollow structure have been investigated in detail. It is worth mentioning that yolk–shell and hollow structures could be obtained by changing the order of the calcination and etching process of the SiO2@TiO2:Eu3+ core–shell structure. Herein, the hollow structure showed the highest luminescence intensity, and the core–shell structure exhibited excellent photocatalytic efficiency for the degradation of methyl orange.