Lignin based slow-release system for nanoherbicides: A green and safe strategy with high foliar deposition and stability

Traditional pesticide formulations exhibit low utilization rates due to poor foliar deposition and instability under UV irradiation during application, which limits their efficacy in enhancing agricultural productivity. This study developed a lignin-based nanocarrier system through solvent-antisolvent precipitation and coordination-driven self-assembly of lignin with Fe³ ⁺-tannic acid (TA) complexes to address these challenges. A nanoherbicide (called PMT@AFT) was prepared using prometryn (PMT) as a model drug. Different preparation conditions of the lignin-based nanocarrier system were systematically investigated to regulate the particle size of the microspheres, as well as the four main properties of the nanopesticide: stability, adhesion, slow-release, and efficacy, to assess its effect on non-target crops. The results showed that the chelating coordination of Fe³ ⁺-TA constructed a cross-linking stabilization layer on the surface of lignin microspheres and formed a typical core-shell structure. This endows it with excellent UV resistance, high blade adhesion performance, and good sustained-release performance, with a long duration of effect, releasing only about 60 % after 70 h. Furthermore, PMT@AFT demonstrated excellent herbicidal efficacy against barnyard grass while significantly reducing phytotoxicity to non-target crops. This study establishes a novel strategy for developing eco-friendly and safer nanopesticide formulations.