Energy transfer between uranyl(VI) and europium(III) in aqueous perchlorate solution

Fluorescence measurements on aqueous solutions containing uranyl(VI) and europium(III) perchlorates have shown that energy transfer from uranyl to europium is pH dependent. The uranyl species involved is not the UO/sub 2//sup 2 +/ ion itself but one or more of the hydrolytic species. Emission spectra of the europium ion in the presence of uranyl indicate the formation of a complex between the lanthanide ion and the hydrolyzed uranyl species. The relative intensities of the europium emission lines, the energy-transfer efficiency and the dependence of energy transfer on concentrations are all consistent with a mechanism which involves this complex.