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.
Amine derivatives of alkoxides such as (3-aminopropyl)trimethoxysilane and (3-(2-aminoethyl)aminopropyl)trimethoxysilane are reagents in the sol−gel process and, at the same time, versatile ligands forming
complexes with transition metal ions (e.g., Cu(II)). One of the major advantages of the sol−gel process is
the possibility of preparing Cu(II) complexes in the interior of and on the surface of organically modified
silicate xerogels. This paper compares Cu(II) complexes prepared in the interior of silica xerogels with
those grafted and anchored onto the surface of such xerogels. Grafting and anchoring require prior
preparation of supports with functionalized surfaces. In the former process Cu(II) ions are chemisorbed,
and in the latter Cu(II) complexes are immobilized by a condensation reaction. The following spectroscopic
results are presented: FT-IR, optical absorption in the visible region, and electron paramagnetic resonance
(EPR). The EPR studies are summarized in three identified models of the coordination sites on the modified
silica xerogel surfaces. The materials studied are put forward as catalyst precursors.
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