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.

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The aim of the present study was to utilize the sol-gel method to synthesize different forms of xerogel matrices for drugs and to investigate how the synthesis conditions and solubility of drugs influence the change of the profile of drug release and the structure of the matrices. Silica xerogels doped with drugs were prepared by the sol-gel method from a hydrolyzed tetraethoxysilane (TEOS) solution containing two model compounds: diclofenac diethylamine, (DD)-a water-soluble drug or ibuprofen, (IB)-a water insoluble drug. Two procedures were used for the synthesis of sol-gel derived materials: one-step procedure (the sol-gel reaction was carried out under acidic or basic conditions) and the two-step procedure (first, hydrolysis of TEOS was carried out under acidic conditions, and then condensation of silanol groups was carried out under basic conditions) in order to obtain samples with altered microstructures. In vitro release studies of drugs revealed a similar release profile in two steps: an initial diffusion-controlled release followed by a slower release rate. In all the cases studied, the released amount of DD was higher and the released time was shorter compared with IB for the same type of matrices. The released amount of drugs from two-step prepared xerogels was always lower than that from one-step base-catalyzed xerogels. One-step acid-catalyzed xerogels proved unsuitable as the carriers for the examined drugs.