Test-strip and smartphone-assisted Eu-TCPE-based ratiometric fluorescence sensor for the ultrasensitive detection of tetracycline

Excessive use of tetracycline (TC) exacerbates environmental pollution and seriously threatens human health. Therefore, it is of great significance to explore an effective approach for detecting TC. In this work, a water-stable and ratiometric luminescent sensor based on a dual-emitting Eu-based metal–organic framework (Eu-TCPE, H4TCPE = tetrakis(4-carboxyphenyl)ethylene) was established through a solvothermal method. Benefiting from the luminescence quenching behavior of H4TCPE linkers through the inner filter effect (IFE) and the enhanced fluorescence emission of Eu3+via the antenna effect, supported by the results of UV-vis absorption spectra and density functional theory (DFT) calculations, the Eu-TCPE sensor exhibited a fast and selective response towards TC detection with a low detection limit of 14 nM in a linear range of 0–50 µM. Application of the Eu-TCPE sensor in real samples of tap water and milk was also investigated. Furthermore, a test-strip-based sensor with the Eu-TCPE probe fixed on the surface was developed for the real-time selective detection of TC in aqueous solution, and the fluorescence color changes of the test strip under UV-light excitation can be captured using the portable online analyzer of a smartphone-color detector App, which showed a handheld platform for the rapid and visual detection of TC in practical applications.