Intermolecular energy transfer from coumarin-120 to rare earth ions (Eu3+, Tb3+) in silica xerogels

Co-doped with coumarin-120 (C120) and rare earth ions (Eu3+and Tb3+) in silica xerogels via sol–gel technique, the fluorescence properties of rare earth ions and the energy transfer process between C120 and rare earth ions were studied. The characteristic fluorescence intensities of Eu3+and Tb3+ions can be increased by a factor of 35 and 8, respectively, as a result of the sensitization of C120 absorption at about 344 nm. The sensitized emission of rare earth ions is through intermolecularly resonant exchange interaction. Because of fluorescence enhancement accompanied by concentration quenching of C120, the fluorescence intensities of Eu3+and Tb3+increase to maximum when the C120 doping concentration is of 0.1 mol%.