<i>Cordia macleodii</i> -Mediated Silver Nanoparticles: A Sustainable and Green Solution for Agricultural Phytopathogen Management

The silver nanoparticles were synthesized utilizing the <i>Cordia macleodii</i> (Griff.) Hook.F. & Thamos plant extract. The synthesis of nanoparticles was confirmed through UV-visible spectroscopy, exhibiting a distinct surface plasmon resonance (SPR) absorbance peak at 425 nm. Fourier-transform infrared spectroscopy (FTIR) analysis results revealed the different characteristic peaks corresponding to functional groups responsible for the reduction and stabilization of the silver nanoparticles. The X-ray diffraction (XRD) analysis confirmed a crystalline cubic structure with an average crystalline size of 13.31 nm. Dynamic light scattering (DLS) analysis revealed a hydrodynamic diameter of 114.50 nm with a polydispersity index (PDI) of 22% and a ζ-potential of -10.7 ± 0.8 mV. Field emission electron microscopy (FE-SEM) analysis of nanoparticles displayed a distinct spherical and oval-like shape with uniform morphology, and Engergy dispersive X-ray (EDX) mapping analysis confirmed the presence of Ag (93.39%), C (2.56%), and O (4.05%) by weight percentage. The High-resolution transmission electron microscopy (HR-TEM) exposed the silver nanoparticles as nearly spherical, with some aggregation, and an average diameter of 24.30 ± 11.13 nm. Inhibition in the growth of phytopathogenic bacteria <i>Erwinia carotovora</i> and <i>Ralstonia solanacearum</i> occurred at a 1000 μg/mL concentration of nanoparticles. Nanoparticles were found to accelerate the formation of reactive oxygen species (ROS). The antifungal activity of silver nanoparticles was observed at different concentrations of the nanoparticles. At a 1500 μg/mL concentration of nanoparticles, inhibition of growth was observed: 53.72% for <i>Alternaria alternata</i>, 59.00% for <i>Aspergillus flavus</i>, 53.23% for <i>Botrytis cinerea,</i> and 56.11% for <i>Fusarium oxysporum</i>. The antioxidant activity of silver nanoparticles showed 18.46% free radical scavenging through DPPH assay and 51.99% through ABTS assay at an 80 μg/mL concentration. This study provides an easy, eco-friendly method to fabricate silver nanoparticles for agricultural and other various applications.