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Background: Fluoroquinolones (FQs) are widely used in livestock and poultry industry because of their satisfactory effects in preventing and treating bacterial infection. However, due to irrational use and poor biodegradability, FQs can easily remain in food animals and further enter the human body through the food chain. Therefore, accurate and sensitive detection of FQs residues in animal-origin food is significant. The traditional methods commonly used for FQs detection have some limitations. Ratiometric fluorescence detection technology has the advantages of fast, sensitive, self-correcting, and easy visualization. However, the reports on the use of ratiometric fluorescence probes for FQs detection are limited., Results: In this work, a novel probe was proposed for ratiometric fluorescent analysis of FQs. In this probe, the fluorescence of dithioerythritol stabilized copper nanoclusters (DTE-Cu NCs) was significantly enhanced due to the Tb 3+ triggered aggregation-induced emission effect. FQs bound Tb 3+ in Tb 3+ /DTE-Cu NCs through carboxyl and carbonyl groups, so that Tb 3+ was effectively sensitized to emit green fluorescence. However, the red fluorescence of DTE-Cu NCs was not interfered. The fluorescence of the probe transformed from red to green with the increase of FQs concentration. Using norfloxacin (NOR), difloxacin (DIF), and enrofloxacin (ENR) as FQs simulants, this probe showed a sensitive linear response ranged from 0.025 to 22.5 μM, with the limits of detection of 9.6 nM, 9.3 nM, and 7.7 nM. The application potential for FQs detection was verified via a standard addition assay of egg samples with the recovery rate of 90.4 %-114.7 %., Significant: The fluorescence probe based on Tb 3+ /DTE-Cu NCs is expected to realize the ratiometric fluorescence sensitive detection of FQs. The establishment of this simple, effective, and rapid detection platform opens up a new way for the detection of FQs residues in animal-origin foods, and also provides a new idea for the design of rapid detection platforms for other hazard factors., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Based on the aggregation-induced emission effect triggered by Al3+, a novel probe was constructed for the ratiometric fluorescence visualization detection of fluoroquinolones (FQs) residues. In this probe, Al3+ cased the glutathione-modified copper nanoclusters (GSH-CuNCs) to aggregate by the interaction with surface carboxyl groups, restricting the intramolecular vibration and rotation of GSH-CuNCs and reducing the non-radiative relaxation of excited states. Significant enhancement of fluorescence and quantum yield were achieved. In the presence of FQs, Al3+/GSH-CuNCs coordinated with FQs to form a polymer that inhibited intramolecular proton transfer in the excited state of FQs, thereby enhancing the intrinsic fluorescence of FQs, while the fluorescence intensity of Al3+/GSH-CuNCs was not disturbed. The probe solution changed from red to blue (or green) under UV lamp as the concentration of FQs increased, providing the possibility for semi-quantitative visual analysis. It also showed sensitive spectral responses to FQs with detection limits of 7.9 (ciprofloxacin), 6.8 (gatifloxacin), and 9.5 nM (enrofloxacin), respectively. The application potential in the detection of FQs residues in poultry eggs was verified by real sample test. Additionally, the probe has been extended to the development of fluorescent test paper and the smartphone detection platform, contributing to rapid, portable, visual quantitative analysis of FQs. [Display omitted] • A fluorescent probe based on the AIE effect of copper nanocluster triggered by Al3+. • Ratiometric fluorescence detection was realized by the coordination of Al3+ and FQs. • The probe changed color from red to blue (or green) under a 365 nm UV lamp. • Fluorescent test strips and a smartphone-based detection platform were developed. [ABSTRACT FROM AUTHOR]