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

Abstract

Europium / Luminescence / Electrolyte / ComplexationSummary. The fluorescence characteristics (lifetime, excitation and emission spectra) of aqueous solutions of Eu(III) containing various supporting electrolytes such as HCl, NaCl, LiCl, CsCl, MgCl 2 , HClO 4 and NaClO 4 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.

EuIII Luminescence in a Hygroscopic Ionic Liquid: Effect of Water and Evidence for a Complexation Process

“…Hence the non-degassed europium solution, which contains approximately 80 H 2 O molecules per Eu III ion, should be better considered as being an emulsion. The emission spectrum of the non-degassed sample (Figure 4, a) is very similar to the one obtained for Eu 3ϩ aq in slightly acidic aqueous solution, [4,10] although the corresponding lifetime is larger (0.159 ms compared with 0.111 ms for Eu 3ϩ aq , see Table 1). The presence of high-energy OϪH oscillators in the inner coordination sphere of Eu III is known to induce a severe quenching of the luminescence.…”

Stability of Divalent Europium in an Ionic Liquid: Spectroscopic Investigations in 1-Methyl-3-butylimidazolium Hexafluorophosphate

“…These results have been attributed to more or less efficient deactivation mechanisms due to the presence of OH bonds in the first solvation sphere of the excited Eu 2+ ions: complexation is said to decrease the efficiency of these energy transfers, because the solvent molecules are not as close to Eu 2+ in the complex as in the case of the free ion, thus allowing luminescence to be detected . The luminescence enhancement of Eu 3+ upon complexation in various solvents was interpreted along similar lines in refs and and was put in question, however, in ref . As is well-known, PF 6 based ionic liquids may contain water, and the BumimPF 6 solutions studied in this work do so (see Table ).…”

Speciation of Eu(iii) hydroxo complexes in aqueous DMSO studied by direct excitation luminescence spectroscopy and their catalytic activity in phosphodiester cleavage

“…Simple neutral electrolytes such as alkali metal chlorides and perchlorates decrease luminescence lifetimes of Eu(III) in water with both anions and cations contributing to the observed effect. 13 It was suggested that the outer-sphere anion binding and long-range interactions between the excited ion and solvent molecules are responsible for the observed variations. Interestingly, perchlorate anions reduce the luminescence lifetime much more strongly than chloride anions.…”