Synthesis and luminescent properties of monodisperse SiO ₂ @SiO₂:Eu(DBM)₃phen microspheres with core-shell structure by sol–gel method

Monodisperse core-shell structured SiO₂@SiO₂:Eu(DBM)₃phen microspheres, as a new kind of fluorescent particles, were fabricated by a seeded growth method in the presence of surfactant CTAB (DBM = dibenzoylmethane, phen = 1,10-phenanthroline, CTAB = cetyltrimethyl ammonium bromide). In this way, a thin mesoporous silica shell doped with Eu(DBM)₃phen was grown on the prepared monodisperse silica colloids. The structures of the as-prepared phosphors were characterized by means of X-ray diffraction, Fourier transform infrared spectrum, thermal gravimetric analysis–differential scanning calorimetry, field emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectrometry, nitrogen adsorption-desorption techniques, and photoluminescence spectra. The experimental results show that the microshpere has a typical core-shell structure with a diameter of about 370 nm, consisting of the silica colloids core with about 340 nm in diameter and mesoporous silica shell doped with europium complexes with an average thickness of about 15 nm. The as-obtained core-shell microspheres exhibit a strong red emission peak originating from electric-dipole transition ⁵D₀ → ⁷F₂ (610 nm) of Eu³⁺ ions under the excitation of 405 nm. Additionally, the photoluminescence intensity increases with the increasing of europium complexes concentration in mesoporous silica shell, and concentration quenching occurs when europium complexes concentration exceeds 7.0 mol%. The prepared microspheres may present potential applications in the fields of optoelectronic devices, bio-imaging, medical diagnosis, and the packing structural functional composites.

Monodisperse core-shell structured SiO₂@SiO₂: Eu(DBM)₃phen microspheres with high lumious performance were fabricated by a seeded growth method by means of surfactant CTAB.