A new two-phase system for the preparation of nearly monodisperse silver nanoparticles

Nearly monodisperse silver nanoparticles were prepared in a two-phase water–cyclohexane system. Aqueous silver nitrate was reduced by the product of the reaction of aqueous hydrazine with benzyl aldehyde in cyclohexane to form, in the presence of oleic acid, cyclohexane-soluble silver nanoparticles. The silver nanoparticles were examined by transmission electron microscopy (TEM), UV–visible spectroscopy (UV–vis), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The nanoparticles are relatively monodisperse (diameter less than 6 nm) and have good stability in cyclohexane due to the oleic acid adsorbed on their surfaces. These silver nanoparticles were successfully assembled into a powder with a face-centered-cubic structure by slow evaporation of the solvent. With some change in particle size, these silver nanoparticles could be transferred from cyclohexane to water by the addition of cetyltrimethylammonium bromide.