Luminescence Behavior of Sol−Gel-Derived Hybrid Materials Resulting from Covalent Grafting of a Chromophore Unit to Different Organically Modified Alkoxysilanes

Abstract

The compounds studied in this work are sol-gel-derived organic-inorganic hybrid materials in which the two components are covalently linked via Si-C bonds. The organic part is a chromophore group derived from dipicolinic acid that is functionalized with trialkoxysilyl groups; the as-obtained silylated monomers are afterward submitted to complexation with rare-earth ions (Eu 3+ , Gd 3+ ) and are used as the siloxane network precursors. The preparation of hybrid materials including covalent grafting and the sol-gel process is described, as well as their luminescence properties. Modifications of the ligand structure (mono-or disubstituted amides) lead to different coordinating properties and to variable absorption edges. As a result, the absorption efficiency or the ability of the chelates to transfer the absorbed energy to Ln 3+ and consequently the quantum yield of the emission are changed. The major effect of silica is a broadening of the emission peaks, whereas spectral repartitions and lifetimes are mainly unchanged as compared with the corresponding organic molecules.

Interpretation of europium(III) spectra

“…These ligands can act as an antenna to absorb the excitation light and to transfer the excitation energy to the higher energy levels of the Eu 3+ ion, from which the emitting excited levels can be populated. The photoluminescence of europium(III) complexes has been studied in solutions [1,2], polymer matrices [3,4], sol-gel glasses [5,6], functionalized sol-gel glasses [7][8][9][10][11], ionogels [12,13], liquid crystals [14][15][16], encapsulated into inorganic hosts such as zeolites [17][18][19][20] and in metal-organic frameworks (MOFs) [21,22]. The design of europium(III)-containing inorganic-organic hybrid materials is a popular research field [23][24][25][26].…”

Photonic and nanobiophotonic properties of luminescent lanthanide-doped hybrid organic–inorganic materials

“…Costela et al have published an interesting review of dye-doped polymer laser gain media 43 and photophysical characteristics have been investigated by Holzer et al 44 Most of the recent dye-doped emitting materials for tunable solid-state lasers are Class II organic-inorganic hybrids prepared by conventional sol-gel techniques in which luminescent lanthanide organic complexes are anchored to a siloxane matrix via Si-C linkages. 45,46 The strategy to prepare such materials is to design new organoalkoxysilanes, which combine a chromophore unit that can efficiently absorb the incident light, chelating functions that can bind to the Ln 3+ ions and trialkoxysilyl groups that act as the inorganic network precursors.…”

Synthesis and characterization of bifunctional terbium complex-based nanoparticles

“…The silica precursor TESPPA was prepared by dissolving 0.4000 g (1.96 mmol) of 2,6-pyridinedicarboxylic acid chloride in 40 mL of dry diethyl ether and degassing under argon [31].…”