Luminescence properties of materials with Eu(III) complexes: Role of ligand, coligand, anion, and matrix

This study focuses on luminescent materials based on the antenna effect and prepared by the sol-gel method. These materials are composed of a Eu(III) complex (luminescence center) entrapped in a xerogel matrix. Luminescence properties of the lanthanide-based emitting materials depend on the efficiency of energy transfer from the absorption center (ligand) to the emission center (central ion) and on the concentration of quenchers (O-H oscillators) surrounding the central ion. In this study, such luminescence properties as * lifetime and quantum yield were improved by modifying the coordination environment of the central ion and changing anion groups and matrixes. The results of the experiments on the composition of the coordination sphere show that a cryptand ligand with aromatic groups and an aromatic coligand efficiently initiate the antenna effect, thus isolating the central ion from every efficient quencher, e.g., water molecules. Luminescence properties also depend on the anion in the Eu(III) complex salt, the type of matrix material, and the concentration of water and OH groups in the matrix. These luminescent materials have been tested for their photochemical stability under continuous UV irradiation.