Preparation and luminescence properties of core–shell structure composites SiO2@ANA-Si–Eu and SiO2@ANA-Si–Eu–L and core–shell–shell structure composites SiO2@ANA-Si–Eu@SiO2 and SiO2@ANA-Si–Eu–L@SiO2

Abstract

In this paper, novel core–shell (CS) structure composites SiO₂@ANA-Si–Eu and SiO₂@ANA-Si–Eu–L (L = phen, TTA) were prepared by the condensation of 5-N-bis(amidopropyltriethoxysilyl) nicotinic acid (HOOCC₅H₄NN(CONH(CH₂)₃Si(OCH₂CH₃)₃)₂, abbreviated as ANA-Si) and a SiO₂ microsphere with a diameter of 200 nm in the absence of surfactants. The as-synthesized CS structure composites possess good dispersion, uniform size and excellent luminescence properties. Furthermore, silica modified core–shell–shell (CSS) structure composites SiO₂@ANA-Si–Eu@SiO₂ and SiO₂@ANA-Si–Eu–L@SiO₂ were successfully prepared by a sol–gel method using CS structure composites as the core and amorphous silica as the shell. Compared with the CS structure composites, CSS structure composites exhibited a stronger luminescence intensity in the solid state. Furthermore, an improved luminescence stability property of the CSS structure composites was found in aqueous medium. CSS structure composites exhibited improved luminescence, high stability and good solubility, which provided potential for their wide use in advanced phosphors, molecular biomarkers and luminescent tracers.