Fluorescent Nanoprobe Based on 2D Al₂O₃ Nanosheets for Clioquinol Detection

We have developed fluorescent two-dimensional Al₂O₃ (2D Al₂O₃) nanosheets based on a highly sensitive and selective sensing of clioquinol (CQ), which is utilized to treat neurodegenerative diseases in potential fluorescence sensor application. The fluorescent 2D probe was developed via the synthesis methods of combining the hydrothermal method with the probe ultrasonication method. It is obviously owing to potassium sulfate and urea, which serve to regulate the morphology of the nanosheets and to produce the intensive fluorescence. As obtained, 2D Al₂O₃ nanosheets exhibit high-intensity blue-green fluorescence with excitation/emission wavelengths of 340 nm and maximum intensity at 450 nm, which were optimized by fluorescence and UV instruments. The fluorescence of the 2D Al₂O₃ nanosheets can be linearly quenched by the increasing concentrations of CQ, and the concentration linear range was observed from 11 nM to 7.6 μM, and a detection limit of 0.7 nM was found. Quenching of fluorescence was caused by the CQ reaction with 2D Al₂O₃ nanosheets through the inner filter effect. Furthermore, the selectivity results demonstrate that the fluorescence of the 2D Al₂O₃ nanosheets is significantly quenched compared to that of other biomolecules. In order to demonstrate that the applicability of the current approach can be applied to real-world analysis, different concentrations of CQ were spiked into human urine and pharmaceutical CQ cream samples, and satisfactory results were achieved.