INVESTIGATION OF FLUORESCENCE EFFICIENCY IN THE EUROPIUM-THENOYLTRIFLUOROACETONE CHELATE IN AQUEOUS AND ETHANOLIC SOLUTIONS BY LASER-INDUCED FLUORESCENCE AND PHOTOTHERMAL SPECTROSCOPIC METHODS

The photophysical characteristics of the europium (III)-thenoyltrifluo roacetone chelate were studied in a micellar Triton X-100 aqueous solu tion and in ethanol in correlation with the strong europium-sensitized fluorescence observed in these media. The properties of the chelate a nd the resulting ion fluorescence intensity were first compared by ste ady-state absorbance and fluorescence experiments. Fluorescence lifeti mes, fluorescence quantum yields and energy transfer efficiencies were then investigated using time-resolved fluorescence and thermal lens m easurements. In ethanol with 10(-2) M acetate buffer, the strong lumin escence of europium represents only some percent of the energy absorbe d by the chelate and the efficiency of energy transfer from the ligand to the ion is calculated to be 0.165. In the aqueous micellar solutio n, the part of radiative energy is still smaller and cannot be measure d by the thermal lens method. However, the analytical sensitivity is q uite comparable because the absorption spectra of the ligand and the c helate are well separate and the lifetime of the lowest excited state D-5(0) of europium(III) is made longer by the micellar environment.