Synthesis and luminescence properties of core-shell SiO2/ANA-Si-Dy and core-shell-shell SiO2/ANA-Si-Dy/SiO2 nanocomposites

The bifunctional organic ligand ((HOOCC₅H₄NN(CONH(CH₂)₃Si(OCH₂CH₃)₃)₂ (abbreviated as ANA-Si) was synthesized using 5-aminonicotinic acid (ANA) and the silane coupling agent 3-(triethoxysilyl)-propyl isocyanate (TEPIC). Simultaneously, two novel nanocomposites core-shell SiO₂/ANA-Si-Dy and core-shell-shell SiO₂/ANA-Si-Dy/SiO₂ were successfully prepared. The prepared nanocomposites were characterized by Fourier transform infrared spectroscopy (IR), ultraviolet-visible spectroscopy (UV-Vis), high-resolution transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. SEM and TEM analysis indicate that the prepared nanocomposite SiO₂/ANA-Si-Dy was a core-shell structure, which formed by SiO₂ microspheres core coated with dysprosium organic complex shell. Correspondingly, the core-shell-shell nanocomposite formed by this core-shell nanocomposite coated with a SiO₂ layer. The further analysis can be found that the diameters of the SiO₂ core, core-shell and core-shell-shell nanocomposites were about 200–205 nm, 220–225 nm and 230–235 nm, respectively. The core-shell-shell nanocomposite was found to have better luminescence intensity and longer lifetime than the core-shell nanocomposite. In addition, the core-shell-shell nanocomposite has excellent luminescence stability in aqueous solution. Therefore, the core-shell-shell nanocomposite with bright luminescence, high stability and long lifetime may present potential applications in the field of biology.