Luminescent materials consisting of Eu(III) ions complexed with cryptand ligand and coligands entrapped in xerogel matrices

Luminescence properties of Eu(III) complexes (with cryptand ligand and coligands) entrapped in different matrices prepared by sol-gel procedure has been investigated. These luminescent materials are based on antenna effect, i.e., energy transfer from the absorbing [biqO2.bpy.bpy] cryptand (eventually coligand) to the emitting central ion. In this study, such luminescence properties as lifetime and quantum yield were improved by modifying the coordination environment of the central ion changing coligands. The results of the studies on the composition of the coordination sphere show that some aromatic coligands enhance the antenna effect. Luminescence properties depend on the concentration of water molecules and OH groups in the matrix. Concentration of these quenchers was reduced by thermal treatment or a chemical reaction. The most intensive luminescence and the highest luminescence quantum yield were observed in the case of {Eu[biqO2.bpy.bpy]}(CF3SO3)3 with phthalic acid (PA) as a coligand in the SiO2-PDMS matrix. Since the materials are excited by UV radiation to emit, they have been tested for their photochemical stability under continuous UV irradiation.