Tuning electrostatic interactions in amine-functionalized lignin-stabilized pickering emulsions for enhanced foliar retention and plant protection

Lignin-based materials show great potential for sustainable pesticide delivery, yet improving foliar retention through electrostatic tuning remains challenging. Here, aminated alkali lignin (AAL) was synthesized via the Mannich reaction to prepare positively charged nanoparticles, which served as stabilizers for Pickering emulsions (PE) to encapsulate pesticide difenoconazole (Dif), achieving over 90 % encapsulation efficiency. Compared to unmodified lignin, the AAL-stabilized PE exhibited enhanced stability, prolonged release performance and improved anti-photolysis effects. Moreover, the introduction of positive charges through amination enabled the tuning the electrostatic interactions between the emulsion droplets and the negatively charged leaf surface. This precise control over electrostatic properties led to enhanced foliar adhesion and reduced pesticide loss. Among them, Pickering emulsions stabilized by triethylenetetramine-modified alkali lignin particles (AL-TETA PE) achieved the highest retention on strawberry leaves, approximately twice that of AL PE. Additionally, Dif@AL-TETA PE exhibited a threefold increase in in vitro fungicidal activity against Colletotrichum gloeosporioides compared to the Dif emulsifiable concentrate (Dif EC), along with improved control efficacy. This study, by tuning electrostatic interactions in amine-functionalized lignin-stabilized Pickering emulsions, provides a promising strategy to enhance foliar retention and improve plant protection, contributing to the development of eco-friendly and efficient pesticide delivery systems for sustainable agriculture.