Green Synthesis of Silver Nanoparticles Using Aqueous Extract of Brucea javanica Residue: Enhanced Herbicidal Activity Against Paddy Weeds and Alleviated Phytotoxicity to Rice

The negative impacts caused by synthetic herbicides have necessitated research on environment-friendly and sustainable alternatives. In this study, a novel botanical nanoherbicide was developed through green synthesis of silver nanoparticles (Ag NPs) assisted by aqueous extract of Brucea javanica (BJ) residue. The BJ-Ag NPs were characterized using ultraviolet–visible (UV–Vis) absorption spectroscopy, dynamic light scattering (DLS), zeta potential analysis, X-ray diffraction (XRD), and transmission electron microscopy (TEM) attached with energy dispersive X-ray spectroscopy (EDX). TEM images indicated that the BJ-Ag NPs were spherical with an average particle size of 12.75 nm. Meanwhile, the herbicidal activity against two paddy weeds (Echinochloa crusgalli and Bidens pilosa L.) and phytotoxicity to rice (Oryza sativa L.) were evaluated using the Petri dish method. Compared to the BJ residue extract, the BJ-Ag NPs exhibited enhanced inhibitory activity on the seed germination and seedling growth of two target weeds, while showing alleviated phytotoxicity and partially restored seedling vigor in rice. Obviously, positive impacts on both the weed and crop were obtained after synthesizing Ag NPs using the BJ residue extract. The results in this study demonstrated the potential of the BJ-Ag NPs as a sustainable, crop-friendly nanoherbicide for weed management in paddy fields.