Molecular design of luminescent organic-inorganic hybrid materials activated by europium (III) ions

• Published in: Solid state sciences Vol. 3; no. 1; pp. 211 - 222
• Main Authors: Franville, Anne-Christine, Mahiou, Rachid, Zambon, Daniel, Cousseins, Jean-Claude
• Format: Journal Article
• Language: English
• Published: Paris Elsevier Masson SAS 01.01.2001; Elsevier
• Subjects: Class II hybrid materials; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Local probe; Luminescence; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Phosphor; Photoluminescence; Physics; Rare-earth organic complexes; Sol–gel; Trivalent europium; Class II hybrid materials; Luminescence; Rare-earth organic complexes; Trivalent europium; Local probe; Sol–gel; Phosphor; NMR; Gadolinium complexes; Phosphors; Dicarboxylic acids; Hybrid systems; Experimental study; Sol-gel process; Europium complexes
• ISSN: 1293-2558; 1873-3085
• DOI: 10.1016/S1293-2558(00)01114-6

Luminescent hybrid materials consisting in rare-earth (Eu 3+, Gd 3+) organic complexes covalently attached to a silica-based network have been obtained by a sol–gel process. Four dicarboxylic acids with different aromatic subunits (dipicolinic acid, 4-phenyl-2,6-pyridinedicarboxylic acid, 4-(phenylethynyl)-2,6-pyridinedicarboxylic acid and 2,6-Bis(3-carboxy-1-pyrazolyl)pyridine) have been chosen as ligands for Ln 3+ ions. They were grafted to 3-aminopropyltriethoxysilane (APTES) to give organically modified alkoxysilanes that were used as molecular precursors for the preparation of hybrid materials. Ln 3+ first coordination sphere, composition of the siloxane matrix and connection between the organic and inorganic parts have been characterized by infrared spectroscopy, by 13C 29Si solid-state NMR as well as by elemental analyses. UV excitation in the organic component resulted in strong emission from Eu 3+ ions due to an efficient ligand-to-metal energy transfer. As compared to reference organic molecules, hybrid samples exhibited similar emission properties under UV excitation in addition to mainly unchanged excited states lifetimes. However, by direct excitation of the Eu 3+- 5D 0 energy level, the presence of two different site distributions were evidenced in the four hybrid compounds. Emission features related to each of these site distributions and their respective attribution were investigated. Variations in the relative emission intensities were observed according to the nature of the organic chromophore. These variations were discussed in relation to the ATE (Absorption-Transfer-Emission) mechanism and to the relative energy positions of the ligand and the rare-earth ions respectively.