An innovative probe based on aluminum ion-triggered aggregation induced emission effect for ratiometric fluorescence visual detection of fluoroquinolone

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.