Rapid and Visual Detection of Bipyridylium Herbicides Based on Polyelectrolyte-Induced Nanoassemblies of Pyrenyl Probes

In this work, we report a novel fluorimetric sensing system for the visual and rapid detection of bipyridylium herbicides (paraquat and diquat) using a polyelectrolyte-induced nanoassembly strategy in 100% aqueous media. This approach relies on the formation of supramolecular assemblies between a pyrenyl probe (N,N,N-trimethyl-4-(pyren-1-yl)­butan-1-aminium bromide, PyBTA) and a polyelectrolyte (poly­(4-styrenesulfonic acid), PSS), which could promote paraquat complexation by the synergy of noncovalent forces such as electrostatic and π–π stacking interactions. Compared with the traditional direct recognition method, the proposed method shows a 500-fold higher sensitivity, and the detection limit is as low as 40 nM. This assay can be performed within 15 s and can be observed by the naked eye with a visual detection limit of 0.5 μM. Excellent selectivity for paraquat and diquat is demonstrated by a comparison with other pesticides and common ions. This method can be applied to monitor paraquat concentrations in vegetable and soil samples. This approach was validated by paraquat spiking experiments at multiple levels (recovery: 101.2%–104.1%; relative standard deviation (RSD): 2.3%–6.1%; uncertainty: 0.014–0.035). To the best of our knowledge, this is the first pyrenyl nanoassembly system constructed for detecting bipyridylium herbicides in aqueous solution. We believe the present work will not only broaden the scope of polyelectrolyte-induced nanoassembly based sensors but also provide important information for the design of novel synergistic methods for rapid detection technology.