Improved photoluminescence properties of a novel europium(III) complex covalently grafted to organically modified silicates

A series of novel organic-inorganic hybrid materials with a Eu(III)complex [(C2H5)(4)N][Eu(DBM)(3)(DBM-OH)] (DBM = dibenzoylmethanate, DBM-OH = p-hydroxydibenzoylmethanate) covalently bonded into vinyl-modified silica networks have been successfully assembled through a sol-gel process. DBM-OH was grafted to the coupling agent 3-(triethoxysilyl)propylisocyanate (TESPIC), and the as-obtained molecular precursor DBM-Si was used as a bridge molecule both coordinate to Eu3+ and forming an inorganic Si-O network with tetraethoxysilane (TEOS) and vinyltriethoxysilane (VTES) after cohydrolysis and co-condensation processes. The luminescence properties of VTES/TEOS composite hybrid materials were systematically studied in comparison to those of TEOS-derived hybrid material and pure [(C2H5)(4)N][Eu(DBM)(4)], respectively. The results indicate that the luminescent quantum efficiencies of VTES/TEOS composite hybrid materials are greatly improved. And it is interesting to find that the luminescent intensity of VTES/TEOS composite hybrid material is enhanced by optimizing the molar ratio of VTES to TEOS (VTES:TEOS = 4:6) by 3.3 and 2.4 times compared with TEOS-derived hybrid material and pure [(C2H5)(4)N][Eu(DBM)(4)], respectively. In addition, the thermal stability of the emission was also improved considerably. The results presented in this paper indicate that the use of vinyl-modified silicates as a matrix opens the door to improving the photoluminescence properties of Eu(III) complexes. (C) 2010 Elsevier Inc. All rights reserved.