Spectral properties of Eu(III) complexes with heteropolyanions immobilised in xerogel matrices

Eu3+ complexes with two heteropolymetalates (HPMs) were entrapped in various xerogel matrices by the sol-gel process. The spectral behaviour of these complexes in the rigid xerogel was studied by means of absorption and emission spectra. The luminescence emission experiments prove that photoexcitation of the HPM lattices (tungstate and molybdate) induced the energy transfer from the oxygen-to-metal charge transfer {O --> M (= W, Mo)} triplet states to Eu3+ (F-7(0.1,2) --> D-5(0.1)). Among the studied matrices with the Eu(III) complexes the best results, i.e. highest relative intensity and longest lifetime, were observed for methylated silicate (SiO2-polydimethylsiloxane) and silica. In both the cases intensity of the emission could be improved by drying at elevated temperature. The studied materials consisting of complexes Eu3+ with the HPMs exhibit in practice stable emission intensity during UV irradiation. (C) 2004 Elsevier B.V. All rights reserved.