Photoexcitation of europium(III) in various electrolytes: dependence of the luminescence lifetime on the type of salts and the ionic strength

The fluorescence characteristics (lifetime, excitation and emission spectra) of aqueous solutions of Eu(III) containing various supporting electrolytes such as HCl, NaCl, LiCl, CsCl, MgCl2, HClO4 and NaClO4 have been measured. The observed lifetime variations cannot be properly described neither through the hydration sphere phenomenological approach nor through a Stern-Volmer relationship. Long-range interactions between the excited ion and solvent molecules, in addition to an outer-sphere complexation with the anions, are proposed to account for the observed variations