Visible and near-infrared luminescent mesoporous titania microspheres functionalized with lanthanide complexes: microstructure and luminescence with visible excitation

Abstract

A new type of monodisperse mesoporous titania microspheres possessing visible (Eu3+, Sm3+) and near-infrared (Sm3+, Yb3+, Nd3+) luminescence were synthesized with covalent linking to Ln(dbm)3bpdc complexes (Ln = Eu, Sm, Yb, Nd, dbm = dibenzoylmethanate, bpdc = 2,2′-bipyridine-4,4′-dicarboxylic acid). These lanthanide complex-functionalized titania microspheres can be excited with visible light to extend the practical application in lighting devices and biomedical analysis. The materials were characterized using Fourier-transform infrared (FT-IR) spectroscopy, wide-angle X-ray powder diffraction (WAXD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), nitrogen adsorption/desorption, diffuse reflectance (DR) spectroscopy, fluorescence spectroscopy, and thermogravimetric analysis. The results show that the microsphere morphology composed of single anatase crystallites and mesoporous structure is retained after linking to the lanthanide complexes. To the best of our knowledge, this is the first successful attempt to graft lanthanide complexes onto mesoporous anatase titania microspheres with high crystallinity. The novel combination of lanthanide complexes with NIR luminescence under visible light excitation and mesoporous titania microspheres with high thermal and chemical stabilities as well as anatase crystallinity affords potential applications in the fields of energy conversion, photocatalysis, and biomaterials.