Chitosan–Citral Imine Hydrogels With Self-Ordered Nanostructures as Sustained-Release and Eco-Friendly Agricultural Fungicide

This study developed chitosan-based hydrogels as field-deployable carriers for sustained fungicide delivery to enhance crop disease resistance and yield. Citral and chitosan were reacted at three molar ratios (N1, N1.5, N2) via acid-catalyzed Schiff-base condensation, and the resulting hydrogels were characterized by FTIR, 1 H NMR, SEM and WXRD. Structural analyses confirmed the formation of self-ordered imine clusters with a d -spacing of 20.5 Å stabilized by non-covalent interactions. N1, the highest-cross-linked hydrogel, showed the best thermal stability ( T 10 = 160°C) and the lowest swelling, releasing 7.0% slower than N1.5 and 37.9% slower than N2. Antifungal assays demonstrated that N1 provided the strongest inhibition against five phytopathogens ( Rhizoctonia solani , Fusarium graminearum , Botrytis cinerea , Rhizoctonia cerealis , and Phytophthora capsici ), improving inhibition of B. cinerea , P. capsici , and F. graminearum by 56.8%, 82.9%, and 181.3%, respectively, compared with free citral. These hydrogels combine antifungal activity, water retention, thermal stability and controlled release, providing a promising strategy for green fungicide delivery in agriculture.