Preparation of silver nanoparticles in hexagonal phase formed by nonionic Triton X-100 surfactant

Silver nanoparticles were prepared by reducing silver ions in the hexagonal phase formed by Triton X-100 in aqueous solution. Triton X-100 molecules have been used to form the hexagonal phase in aqueous solution as well as to reduce the silver ions into silver atoms. The hexagonal phase hindered the growth and aggregation of particles. The microstructure of the hexagonal phase was investigated by polarizing microscopy, H-2 NMR spectroscopy and small-angle X-ray diffraction. At the initial stage of the reaction, silver particles prepared in the hexagonal phase exhibited a size of 1-7 nm. As the reaction proceeded, particles grew up to about 30 nm as determined by transmission electron microscopy (TEM). The formation rate of silver particles was investigated by UV-Visible spectroscopy. It was found that the reaction temperature was an important factor for the rate of particle formation. With TEM, it was confirmed that surfactant aggregates, which have flexible structures, could not absolutely prevent particles from growing and aggregating. But, the results of polarizing microscopy, H-2 NMR spectroscopy and X-ray diffraction exhibited that the growth of particles could not cause a deformation of the original structure (hexagonal phase), which was employed as the reaction medium. (C) 2002 Elsevier Science B.V. All rights reserved.