ANTENNA EFFECT IN AN OXIDE XEROGEL

Silica xerogel doped with [Eu subset of cryptand](3+) was prepared by the sol-gel method from a hydrolyzed tetramethoxysilane solution conta ining [Eu subset of cryptand](CF3SO3)(2)Br. UV-visible optical absorpt ion spectra, fluorescence excitation and emission spectra, fluorescenc e lifetime as well as luminescence quantum yield were measured. Experi ments were carried out in aqueous solution and in rigid silica xerogel at room temperature. It is shown that the excitation is centred on th e ligand, but the metal ion takes part in the emission process. In oth er words, the antenna effect was observed in the Eu(III) cryptate stud ied in the solution and xerogel. The cryptate entrapped in the xerogel showed higher emission efficiency and longer lifetime than in solutio n. (C) 1998 Elsevier Science B.V. All rights reserved.