Synthesis, characterization and luminescence of europium perchlorate with MABA-Si complex and coating structure SiO₂...

This article reports a novel category of coating structure SiO₂ @Eu(MABA-Si) luminescence nanoparticles (NPs) consisting of a unique organic shell, composed of perchlorate europium(III) complex, and an inorganic core, composed of silica. The binary complex Eu(MABA-Si)₃ ·(ClO₄ )₃ ·5H₂ O was synthesized using HOOCC₆ H₄ N(CONH(CH₂ )₃ Si(OCH₂ CH₃ )₃ )₂ (MABA-Si) and was used as a ligand. Furthermore, the as-prepared silica NPs were successfully coated with the -Si(OCH₂ CH₃ )₃ group of MABA-Si to form Si-O-Si chemical bonds by means of the hydrolyzation of MABA-Si. The binary complexes were characterized by elemental analysis, molar conductivity and coordination titration analysis. The results indicated that the composition of the binary complex was Eu(MABA-Si)₃ ·(ClO₄ )₃ ·5H₂ O. Coating structure SiO₂ @Eu(MABA-Si) NPs were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and infrared (IR) spectra. Based on the SEM and TEM measurements, the diameter of core-SiO₂ particles was ~400 and 600 nm, and the thickness of the cladding layer Eu(MABA-Si) was ~20 nm. In the binary complex Eu(MABA-Si)₃ ·(ClO₄ )₃ ·5H₂ O, the fluorescence spectra illustrated that the energy of the ligand MABA-Si transferred to the energy level for the excitation state of europium(III) ion. Coating structure SiO₂ @Eu(MABA-Si) NPs exhibited intense red luminescence compared with the binary complex. The fluorescence lifetime and fluorescence quantum efficiency of the binary complex and of the coating structure NPs were also calculated. The way in which the size of core-SiO₂ spheres influences the luminescence was also studied. Moreover, the luminescent mechanisms of the complex were studied and explained.