Europium(III) Complex-Functionalized SiO₂@mTiO₂ Nanospheres for Al³⁺-Modulated Multicolor Emission

A europium(III) hybrid material Eu(tta)₃bpdc-SiO₂@mTiO₂ (Htta = 2-thenoyltrifluoroacetone, H₂bpdc = 2,2'-bipyridine-3,3'-dicarboxylic acid) was successfully designed and synthesized by the covalent grafting complex Eu(tta)₃bpdc to SiO₂@mTiO₂ core-shell nanosphere. The FT-IR, PXRD, XPS, TEM, HRTEM, SAED, TGA and PL were performed to characterize these materials. The results indicate that core-shell nanosphere structure and anatase crystallites of SiO₂@mTiO₂ are retained well after grafting the europium complex. Hybrid material Eu(tta)₃bpdc-SiO₂@mTiO₂ displays uniform nanosphere structure, bright red color and long lifetime, which can serve as a multicolor emission material modulated by using Al³⁺ ions via the cation exchange approach under a single-wavelength excitation. To the best of our knowledge, this work is the first multicolor emissive sensor for Al³⁺ ions based on the lanthanide hybrid material.