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Keywords:

  • Organic-inorganic hybrid composites;
  • Europium;
  • Luminescence;
  • Composite xerogels

Abstract

Polysilsesquioxane bridges are obtained through the single modification of 3-(triethoxysilyl)propyl isocyanate (TEPIC) by two β-diketone ligands [thenoyltrifluoroacetylacetone (TTA) and trifluoroacetylacetone (TA)], which behave as linkages between the europium ion and composite host Si–O–M (M = B or Ti) xerogels by controlling the hydrolysis rate of the alkoxy compounds (tetraethyl orthosilicate, titanium butoxide and tributyl borate). Subsequently, luminescent europium hybrid xerogels are assembled and characterized by NMR, Fourier transform infrared (FTIR), ultraviolet absorption and ultraviolet/visible diffuse reflection spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and photoluminescence spectroscopy through which the decay times (τ) and quantum efficiency (η) can be determined. These results reveal that the lanthanide complexes have been covalently immobilized into the composite inorganic xerogels and the obtained hybrids have the excellent ability of light absorption and emission. The hybrids with composite Si–O–B xerogels possess the matched photoluminescent properties (red emission intensity, lifetimes, and quantum efficiency) as the pure silica oxygen network, both of which show a superior luminescence performance than the hybrids with composite Si–O–Ti xerogels. Besides, the single modification of TTA is favorable for the luminescence of the hybrid xerogels.