Photothermal controlled‐release microcapsule pesticide delivery systems constructed with sodium lignosulfonate and transition metal ions: construction, efficacy and on‐demand pesticide delivery

BACKGROUND Widespread application of controlled‐release pesticide delivery systems is a feasible and effective method to improve the utilization efficiency of pesticides. However, owing to the high cost and complicated preparation technologies of controlled‐release pesticide delivery systems, their applications in agricultural production have been seriously hindered. RESULTS This study aimed to construct inexpensive photothermally controlled‐release pesticide delivery systems using chitosan (CS) and sodium lignosulfonate (LS) as the wall materials, and a coordination assembly strategy of LS with transition metal ions to encapsulate a model pesticide, avermectin (AVM). The resulting complex or nanoparticle photothermal layers in these systems effectively achieved photothermal conversions, and replaced the use of common photothermal agents. In the prepared pesticide‐delivery systems, two systems had remarkable photothermal conversion performance and photothermal stabilities with a photothermal conversion efficiency (η) of 24.03% and 28.82%, respectively, under 808 nm, 2 W near‐infrared irradiation. The slow‐release and ultraviolet‐shielding performance of these two systems were markedly enhanced compared with other formulations. The insecticidal activities of these two systems against Plutella xylostella under irradiation with light‐emitting diode (LED)‐simulated sunlight were also enhanced by 5.20‐ and 5.06‐fold, respectively, compared with that without irradiation of LED‐simulated sunlight. CONCLUSION Because of their convenient preparations, inexpensive and renewable raw materials, and excellent photothermally controlled‐release performance, these on‐demand pesticide delivery systems might have significant potential in improving the utilization efficiency of pesticides in modern agriculture. © 2024 Society of Chemical Industry. Fabrication process and photothermally controlled‐release of the prepared AVM@CS@LS‐M microcapsule pesticide‐delivery systems. Sodium lignosulfonate–Fe complex or a silver nanoparticle photothermal layer was formed on the surface of the microcapsule. These two on‐demand pesticide‐delivery systems might have significant potential in improving the utilization efficiency of pesticides in modern agriculture.