Fast and Eco–friendly Microwave‐Assisted Synthesis of Silver Nanoparticles using Rosemary Essential Oil as Renewable Reducing Agent

A green and fast methodology was developed to synthesize silver nanoparticles using rosemary essential oil (EO) as a renewable reducing agent. The synthesis process was microwave (MW) assisted, using a coaxial dipole antenna immersed into the reaction medium. This configuration was used to promote both: i) rosemary EO extraction by hydrodistillation, and ii) silver nanoparticle synthesis in an aqueous solution at atmospheric pressure. The effect of two different silver salt substrates and the time reaction on the morphology of the silver nanoparticles was explored. The coaxial microwave‐assisted hydrodistillation of rosemary yields 0.4 % (w/w) in 30 min and contains ethers (17 %), ketones (50 %) and alcohols (15 %). Silver nanoparticles with a tuneable particle size (from 7 to 18 nm) and morphology (from spherical to round‐like shapes) were obtained in reaction times ranging from 2 to 30 min. The nanoparticle formation was followed by UV‐vis spectroscopy and SEM imaging. An ultrafast green synthesis of silver nanoparticles with a tuneable size and morphology, using a combined system of silver salts, rosemary EO and MW is shown. The new reduction agent is available worldwide, non‐expensive and it poses intrinsic antibacterial and antioxidant activities that it may act in synergy to improve the performance of silver nanoparticles as antibacterial agents.