Fluorescent polymeric thin films for selective and sensitive paraquat detection and removal from contaminated...

Paraquat, a widely used herbicide, remains a major concern due to its lethal effects on human health, food safety, and environmental sustainability. Achieving a rapid, selective, and sensitive on-site detection and removal continues to pose a difficulty. This study proposes a fluorescent polymeric probe (P1) for paraquat detection via a fluorescence "turn-off" method facilitated by photo-induced electron transfer mechanism. P1 was synthesized by Free Radical Polymerization, comprises the hydrophilic monomer N,N'-dimethylacrylamide, the paraquat recognition unit pyren-1-ylmethyl methacrylate, and the substrate cross-linking unit benzophenone acrylamide. P1 demonstrated remarkable selectivity for paraquat, effectively distinguishing it from structurally analogous herbicides and metal ions present in real samples. When utilized as a polymeric thin film (F1) on a glass substrate, the probe exhibited significantly improved sensitivity, achieving a detection limit of 0.011 mM and a Stern-Volmer constant of 1.05 × 10⁴ M⁻¹ . The portable F1 device demonstrated reliable and accurate paraquat detection across a range of real-world contaminated samples, including water sources, soil, apples, and lettuce. In addition to its exceptional sensing capabilities, F1 effectively removed paraquat from a complex herbicide mixture with 100 % efficiency. Its remarkable reusability over four consecutive cycles underscores its practicality, cost-effectiveness, and strong potential for large-scale environmental remediation applications.