Fabrication and characterization of molecular hybrid materials with lanthanides covalently bonded in silica via sol–gel process

Tetraethoxysilane (abbreviated as TEOS) and a kind of monomer (abbreviated as PMA–APES) derived from modifying phenylmalonic acid with double carboxylate groups (abbreviated as PMA) with (3-aminopropyl)triethoxysilane (abbreviated as APES) were used as the inorganic and organic compounds respectively. Coordination reaction between lanthanides and the two –CO groups of the monomer happened simultaneously. The resulting material exhibits strong red-colored fluorescence (Eu3+) and green-colored fluorescence (Tb3+), suggesting the intramolecular energy transfer caused by coordination effect of the organic counterpart. IR, NMR, UV/vis absorption, low-temperature phosphorescence and fluorescence spectroscopy were applied for characterization of the material and the above spectroscopic data revealed that the triplet state energy of organic ligand matches with the emissive energy level of europium and terbium ions and effective intramolecular energy transfer process in these molecular hybrid systems.