A red-emitting Europium(III) complex as a luminescent probe with large Stokes shift for the sequential determination of Cu2+ and biothiols in real samples

In this work, a novel Eu3+-DTPA-bis(AMC) complex with red luminescence was designed and synthesized for sequential detection of Cu(2+ )and biothiols (Cys/Hcy/GSH) based on the displacement strategy with the good selectivity, high sensitivity, and large Stokes shift (288 nm). The possible detection mechanism was verified by UV-vis, the high-resolution mass spectrometry, and the fluorescence decay curve. The experimental parameters, including the solution pH, the incubation time, the concentration ratio of Eu3+-DTPA-bis(AMC) to Cu2+ and biothiols concentration, were optimized. Under the optimal conditions, it shows a good linear relationship be-tween the concentration (0-10 mu M) of Cu2+ and the fluorescence intensity of Eu3+-DTPA-bis(AMC), with a low detection limit of 0.065 mu M. The linear range and the limit of detection of the Eu3+-DTPA-bis(AMC)/Cu2+ system for Cys/Hcy/GSH were 2.5-22.5/5-45/5-50 mu M and 0.11/0.07/0.05 mu M, respectively. Surprisingly, the high or low concentration of Eu3+-DTPA-bis(AMC)/Cu(2+ )can significantly affect the selectivity of the sensing system to biothiols (Cys/GSH/Hcy). When the concentration of the Eu3+-DTPA-bis(AMC)/Cu2+ system is 10.0 mu\M, it could recognize biothiols (Cys/GSH/Hcy) from other substances, but when the concentration is as low as 3.3 mu M, it could further specifically distinguished Cys from Hcy/GSH. Owing to the high anti-interference characteristics, accuracy and specificity, the sensing system was well applied to the cascade detection of Cu(2+ )in actual environmental samples and Cys in biological and food samples, including FBS, urine, milk, beverage, fresh juice with the satisfactory recoveries from 96.20 to 106.80 %.

Automated summary

A novel luminescent complex with red color was synthesized for sequential detection of Cu2+ and biothiols. The sensing system showed good selectivity, high sensitivity, and a large Stokes shift.