Eu-polyaspartic acid based ratiometric fluorescent probes for ultrasensitive and visual detection of tetracycline and copper ions in food samples

The visualization and accurate on-site detection of tetracycline and Cu2+ residues in food are essential for maintaining food safety and public health. A novel poly (aspartic acid) Ratiometric fluorescent probe was designed for the sensitive visual detection of tetracycline (Tc) and Cu2+ using the EDTA-Eu3+ complex as the sensing unit and fluorescein dye as the internal standard. The fluorescence of Eu3+ at 617 nm was turned on significantly by Tc via the “antenna effect” and can be quenched by Cu2+ owing to the inner filter effect. The probes selectively detected Tc and Cu2+ over a wide linear range, low LODs of 10 nM and 333 nM, respectively, were obtained. A smartphone APP and probe-loaded test paper were also assembled into a biomass-based portable sensor for visual point-of-use analysis. The fabricated sensors successfully monitored the Tc and Cu2+ levels in milk, honey, and tap water samples, suggesting their broad applications in food safety monitoring and environmental analysis. •First design of a poly(aspartic acid) ratiometric fluorescent probe for the detection of tetracycline and Cu2+.•Low LODs of 10 nM and 333 nM for tetracycline and Cu2+, respectively.•Smartphone-based portable platform for the real-time and on-site detection of tetracycline and Cu2+ in food samples.