Jean-Claude Bunzli - Europium and terbium tris(dipicolinates) as secondary standards for quantum yield determination

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      Publication Details (including relevant citation   information):

      Chauvin,A.S., Gumy,F., Imbert,D., Bunzli,J.C.G. Spectroscopy   Letters 2004 37 (5) 517-

      Abstract: Aqueous. solutions of europium(III)   and terbium(III) tris(dipicolinates), around physiological pH are   shown to be convenient secondary standards in the determination   of quantum yields of lanthanide complexes containing these ions.   Conditions for which a strict linearity is observed between the   concentration of the solutions and the emission intensity are   established. The speciation in these solutions, which contain a   non-negligible amount of bis species is presented and discussed   on the basis of both stability con stants and lifetime   determinations of the Eu(D-5(0)) level. The Q(L)(Eu) quantum   yield Q(L)(Eu) displays a strong pH-dependence: for a solution   with an absorbance of 0.30, it increases sharply from about 2% at   pH 2.5 to reach 11.5-12.5% in the pH range of 6-9. The proposed   standard for Eu-III is a solution Of Cs-3[Eu(dpa)(3)] 7.5 x   10(-5) M in tris buffer 0.1 M (absorbance = 0.20) with a quantum   yield of 13.5% +/- 1.5% under excitation at 279 nm. For Tb-III,   we propose a standard solution of Cs-3[Tb(dpa)(3)] 6.5 x 10(-5) M   in tris buffer 0.1 M (absorbance = 0. 18) with a quantum yield of   26.5% +/- 2% under excitation at 279nm. Despite the speciation   between his and tris complexes, these two standard buffered   solutions present a constant quantum yield within a reasonably   large range of concentration and they are easy to handle, which   makes them adequate for laboratory use

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