Phytotoxicity of Green-Synthesized Ag-Zn Nanoparticles in Maize Seedlings Using Response Surface Method

The use of nanoparticles (NPs) synthesized from plant extracts is an alternative to conventional pesticides for the control of agricultural pests. This study aimed to optimize the conditions of synthesis of silver–zinc nanoparticles (Ag-ZnNPs) using extracts of Ocimum basilicum L. and Crotalaria longirostrata Hook. & Arn. and to evaluate their phytotoxic impact on maize seedlings. The Ag-ZnNPs (Ag-Zn nanoparticles) were synthesized by redox reaction between metal ions and reducing metabolites present in the extracts. A response surface methodology (RSM) with three factors (extract concentration, heating time and pressure) was applied to determine the optimal synthesis conditions. The phytotoxicity of nanoparticles (NPs) on maize seedlings was subsequently evaluated on root growth, oxidative stress enzymes (CAT, POD, and APX), and physiology of seedlings. Nanoparticles synthesized from C. longirostrata extract demonstrated superior properties, with an optimization of synthesis (R2 = 95.3%) where the extract concentration (1:4 v/v; p < 0.01) was the critical factor influencing the reduction of metallic ions to nanoparticles. These NPs exhibited superior stability, smaller size (