INTERMOLECULAR ENERGY-TRANSFER FROM COUMARIN-120 TO RARE-EARTH IONS (EU3+, TB3+) IN SILICA XEROGELS

Go-doped with coumarin-120 (C120) and rare earth ions (Eu3+ and Tb3+) in silica xerogels via sor-gel technique, the fluorescence properties of rare earth ions and the energy transfer process between C120 and ra re earth ions were studied. The characteristic fluorescence intensitie s of Eu3+ and Tb3+ ions can be increased by a factor of 35 and 8, resp ectively, as a result of the sensitization of C120 absorption at about 334 nm. The sensitized emission of rare earth ions is through intermo lecularly resonant exchange interaction. Because of fluorescence enhan cement accompanied by concentration quenching of C120, the fluorescenc e intensities of Eu3+ and Tb3+ increase to maximum when the C120 dopin g concentration is of 0.1 mol%. (C) 1998 Elsevier Science S.A. All rig hts reserved.