A new and efficient luminescence enhancement system of Eu–N-(3,5-dibromosalicylidene)-2-aminopyridine–1,10-phenanthroline and its application in the determination of trace amounts of europium

A sensitive luminescence enhancement system has been developed for the determination of trace amounts of trivalent europium. The luminescence intensity of europium complex with N-(3,5-dibromosalicylidene)-2-aminopyridine (HL) was greatly enhanced after the addition of 1,10-phenanthroline (Phen) in acetonitrile solution. The excitation and emission wavelengths were 274 and 617 nm respectively. Under optimal conditions, the luminescence intensities varied linearly with Eu3+ concentration in the range of 4.0 × 10−6 ∼ 2.4 × 10−5 mol L−1 with a detection limit of 4.3 × 10−10 mol L−1. This method was successfully applied to determine the trace amounts of Eu3+ in a high purity Gd2O3 matrix and in a mixed lanthanide sample. Energy transfer mechanism and luminescence enhancement of HL–Phen–Eu ternary system were studied. The results indicate that both HL and Phen are good sensitizers for the luminescence of Eu3+ ions, as energy gap between the lowest triplet level of HL/Phen and the resonant level of Eu3+ (5D1) exists around the optimal value (3000 ± 500 cm−1). The interference by some other lanthanide ions and common ions were also studied.

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► A new ternary system composed of Schiff base, phenanthroline and Eu is estabilished.
► A simple yet sensitive method is built to determine trace amounts of Eu3+.
► The energy transfer mechanism of the system is studied.
► The luminescence enhancement is explained.