Autoclave mediated one-pot-one-minute synthesis of AgNPs and Au-Ag nanocomposite from Melia azedarach bark extract with antimicrobial activity against food pathogens

Background: The increasing use of nanoparticles and nanocomposite in pharmaceutical and processed food industry have increased the demand for nontoxic and inert metallic nanostructures. Chemical and physical method of synthesis of nanostructures is most popular in industrial production, despite the fact that these methods are labor intensive and/or generate toxic effluents. There has been an increasing demand for rapid, ecofriendly and relatively cheaper synthesis of nanostructures. Methods: Here, we propose a strategy, for one-minute green synthesis of AgNPs and a one-pot one-minute green synthesis of Au-Ag nanocomposite, using Melia azedarach bark aqueous extract as reducing agent. The hydrothermal mechanism of the autoclave technology has been successfully used in this study to accelerate the nucleation and growth of nano-crystals. Results: The study also presents high antimicrobial potential of the synthesized nano solutions against common food and water born pathogens. The multistep characterization and analysis of the synthesized nanomaterial samples, using UV-visible spectroscopy, ICP-MS, FT-IR, EDX, XRD, HR-TEM and FE-SEM, also reveal the reaction dynamics of AgNO3, AuCl3 and plant extract in synthesis of the nanoparticles and nanocomposite. Conclusions: The antimicrobial effectiveness of the synthesized Au-Ag nanocomposite, with high gold to silver ratio, reduces the dependency on the AgNPs, which is considered to be environmentally more toxic than the gold counterpart. We hope that this new strategy will change the present course of green synthesis. The rapidity of synthesis will also help in industrial scale green production of nanostructures using Melia azedarach.