Pyranine-Grafted Nanoporous Membranes for Sensing Paraquat Derivatives

Toxic agricultural pollutants in the environment, such as paraquats, are harmful to human beings. In this study, we provide a feasible method for sensing three kinds of paraquat derivatives. Anodic aluminum oxide (AAO) membranes are used as substrates to detect paraquat derivatives owing to their properties of highly porous structures and chemical stabilities. After pyranine molecules are chemically modified on the surface of AAO templates, pyranine-grafted AAO (P-AAO) membranes are obtained, which can be used for sensing paraquat derivatives by π–π electron stacking interactions, Coulombic attractions, and charge-transfer interactions. The changes of absorption intensities in ultraviolet–visible (UV–vis) spectra and alternations of impedance in Nyquist plots are observed by sensing the paraquat derivatives with P-AAO membranes. The P-AAO membranes show remarkable sensibility and immediacy during the processes of sensing paraquat derivatives, and the limit of detection (LoD) reaches 0.9 μM. This work successfully demonstrates that P-AAO membranes can be an excellent choice for detecting pollutants in the environment and industry.