User safety and herbicidal efficacy of innovative paraquat nanoherbicides based on MIL-101(Cr)@MoS2@Fe3O4 nanomaterials

The widespread global use of paraquat (PQ) is attributed to its high herbicidal efficacy and low cost, however, the unresolved issue of its fatal toxicity to humans after ingestion remains a major challenge. The nanocarriers MIL-101(Cr)@MoS 2 @Fe 3 O 4 (MMF) are synthesized to load PQ through the strong π–p electron coupling between the delocalized π electrons of PQ and the localized p electrons of S atoms of MoS 2 at the interface, and then encapsulated with chitosan to construct magnetically recyclable PQ nanoherbicides with excellent stability and biosafety. The release of PQ from the nanoherbicides in simulated human gastrointestinal environments is inhibited (“PASS0” logic gate) from the source, thereby enhancing user safety. Under natural sunlight conditions, the near-infrared photothermal effect of MMF weakens the strong interfacial π–p electron coupling between PQ and MMF, resulting in the release of PQ (“YES” logic gate). The PQ nanoherbicides maintain the herbicidal efficacy of bare PQ in practical applications. The residual nanoherbicides can be easily recovered using magnets, with the collection ratios of 97.8 % and 91.1 % in water and soil, respectively, at a magnetic field strength of 0.5 T. Seed dressing, cytotoxicity, and mouse models demonstrate that the nanoherbicides have excellent biosafety for both plant growth and PQ-ingesting users. The creative PQ nanoherbicides simultaneously address the challenging issues of user safety, herbicidal efficacy, and environmental friendliness from the source.