Bifunctional ratiometric fluorescent probe for sensing anthrax spore biomarker and tetracycline at different...

Multifunctional fluorescent probes have received increasing attention for the sake of atom economy and high-density integration. Herein, CdTe quantum dots (QDs) modified with Eu³⁺ were synthesized as the bifunctional ratiometric fluorescent probe for sensing two hazardous substances tetracycline (TC) and anthrax spore biomarker 2,6-dipicolinic acid (DPA) at different excitation channels, based on the discrepant excitation wavelengths of Eu³⁺ and the fluorescence quenching of CdTe QDs after interaction with them. Both DPA and TC enhanced the red emission of Eu³⁺ via antenna effect but caused the green emission of CdTe QDs to quench. Interestingly, the excitation wavelengths of Eu³⁺ after coordinating with DPA and TC were 275 and 386 nm, respectively. On this basis, CdTe QDs-Eu³⁺ achieved the bifunctional ratiometric detection of DPA (λ_ex = 275 nm) and TC (λ_ex = 386 nm) with different excitation channels. Both DPA and TC were selectively detected by CdTe QDs-Eu³⁺ with rapid response (DPA-1 min, TC-1 min) and high sensitivity (DPA-LOD 0.3 μM, TC-LOD 2.2 nM). CdTe QDs-Eu³⁺ were applied to analyzing DPA and TC in food, biological and environmental samples. Satisfactory spiked recoveries (80.0-119.0 %) and relative standard deviations (0.5-8.4 %) were obtained for measuring DPA and TC in these samples.