Low swelling Alginate/Lignin network gels with redox responsiveness for sustained release of agricultural fungicide and Pb2+ complexation

Fungicides are among the most essential agrochemicals for controlling crop diseases. However, the increased consumption of fungicides has resulted in environmental pollution and adversely affected human health. The slow-release technology can improve the efficacy and reduce the required amount of fungicide. Here, we developed a low-swelling redox-responsive alginate/lignin network bearing covalently conjugated fungicide thymol-Cl. Natural reductants in the environment caused the selective cleavage of disulfide bonds and release of thymol-Cl and thiazolidin-2-one (a by-product), which both could inhibit the phytopathogenic fungus (F. oxysporum). At the same time, metal chelating groups in the gel endow strong interactions with heavy metal ions for improving soil remediation and preventing the adsorption of toxic metals by the plant roots. The fungicide-loaded carrier could alleviate the poisonous effect of fungi on maize seeds. Indeed, the secretion of natural reducing agents by fungi and maize led to the cleavage of disulfide bonds and the release of fungicides.