Fluorescence enhancement by gadolinium of the europium or samarium-dibenzoylmethane-diethylamine system

A fluorescence enhancement produced by adding Gd³⁺, Y³⁺, Tb³⁺, La³⁺ or Lu³⁺ to europium or samarium-dibenzoylmethane-diethylamine was observed. Gd³⁺ enhanced the fluorescence intensity by 2–3 orders of magnitude compared with the system without Gd³⁺. The new system was used for the simultaneous determination of traces of Sm³⁺ and Eu³⁺ in the ranges 1.0 × 10^?9?8.0 × 10^?8 M and 1.0 × 10^?11?4.0 × 10^?9 M, respectively, and the detection limits were 5 × 10^?13 M for Sm³⁺ and 8 × 10^?14 M for Eu³⁺. The luminescence mechanism of the system is discussed.