Facile sunlight-irradiation mediated green synthesis of highly stable silver nanoparticles using Archidendron bubalinum pods extract for antibacterial activity application

The current study successfully reported biosynthesized silver nanoparticles (bio-AgNPs) using an efficient green route, employing Archidendron bubalinum pods extract as reducing and stabilizing agent under sunlight irradiation. A. bubalinum pod extract contains several fatty acid macromolecules, such as palmitic acid, stearic acid, cinnamic acid, and oleic acid. Those compounds contain hydroxyl and carboxyl groups, which play a crucial role in the reduction process of Ag ions to form Ag nanoparticles. UV–Visible spectrophotometry confirmed the formation of bio-AgNPs. The Energy Dispersive X-ray spectroscopy (EDS) and X-ray Diffraction (XRD) also supported the bio-AgNPs formation, consisting of 67.42 % of Ag in a crystalline form. Meanwhile, the materials size was confirmed by Dynamic Light Scattering (DLS), resulting in an average size of 58.9 ± 7.6 nm. This result aligned with Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM), and was confirmed that the material had spherical AgNPs capped with a thin layer. Moreover, this method resulted in stable bio-AgNPs with a surface charge of −32.4 ± 0.35 mV that were stable for over 3 months. Further, the materials were tested against Staphylococcus aureus ATCC6633 and Gram-negative Escherichia coli ATCC6633 bacteria using inhibition test, MIC, and MBC, demonstrating a good inhibition.