Controllable preparation and mechanism of nano-silver mediated by the microemulsion system of the clove oil

A clove oil microemulsion system was proposed for preparing silver nanoparticles (Ag-NPs). The effects of the clove oil concentration and the reaction time on the formation of Ag-NPs were investigated. The synthesized Ag-NPs was characterized by UV–Vis, X-ray diffraction and high resolution transmission electron microscopy. It was found that the clove oil acted as a reducing agent and a stabilizer in the formation of silver nanoparticles. The mechanism was that Ag+ was adsorbed on the oil–water interface by the active groups of the clove oil in the microemulsion in which it was then reduced to nano-Ag. Furthermore, microspheres were formed on the surface of nano-Ag through complexation of macromolecular substances. Alkyl and aromatic hydrophobic groups that were distributed on the surface of nano-Ag were driven into the clove oil phase under the promotion of Gibbs free energy. Thus, Ag nano-particles with good dispersibility and stability were obtained. The infrared spectrum shows that the outer layer of the nanoparticles coated with active groups of clove oil, which can give the silver nanoparticles better antibacterial. Ag nano-particles of spherical, polygonal, and rod-like shapes were achieved by controlling the initial clove oil concentration and the reaction time.