Preparation And Properties Of Metal Nanoparticles

Metal nanometer material is an important kind of nanometer materials, and it is the basis key material of preparing many kinds of new functional materials. In recent years, metal nanometer material has received extensive attention. With the development of metal nanometer material research, the preparation technology becomes increasingly important. Due to the small size of metal nanoparticles and high surface energy, metal nanoparticles are extremely unstable, leading to the fact that metal nanoparticles are easy to be aggregated and oxidized. It seems difficult to prepare metallic nanoparticles with uniform dispersion, narrow size distribution, and good stability from traditional preparation methods. In our study, several metal nanoparticles, including Ni, Cu, Ag and Pt, were prepared through sol-gel process. The aim of this study is to find a new way of preparation of typical metallic nanoparticles and extending the application field of conventional sol-gel process. To the best of our knowledge, this is the first report of preparation of Ag and Pd noble metallic nanoparticles. The main results in our work are summarized as follows:(1) Ni nanoparticles with small size, narrow size distribution have been successfully obtained through the aqueous solution based sol-gel process where typical polysaccharide(glucose, starch), carboxylic acids(lactic acid, citric acid), poly alcohols(ethylene glycol, glycerine), amines(N,N-dimethylacetamide) or aldehydes(glutaraldehyde) were used as coordination agent, PVP or hexadecylamine was used as surfactant; Ag and Pd nanoparticles have been synthesized where lactic acid, starch were used as coordination agent; the spherical Cu nanoparticles with diameters about 20nm can be obtained where lactose was used as coordination agent.(2) The crystal structure, morphology, chemical composition, magnetic properties of prepared Ni, Ag, Pd, Cu nanoparticles were characterized by X-ray diffraction(XRD), selected area electron diffraction(SAED), transmission electron microscope(TEM), high-resolution transmission electron microscopy(HRTEM), X-ray energy dispersive spectrometer(EDS), vibrating sample magnetometer(VSM). It was observed that the obtained metal nanoparticles have good crystallinity, most of the particles are spherical, and uniformly.(3) The results show that the grain size of metal nanoparticles increases with the increasing of the heat treatment temperature. At the same heat treatment temperature, the size of the nanoparticles gradually decreases with the increase of pH value. Hcp nickel tends to generate at low temperature, when the heating treatments are performed at higher temperatures, diffraction peaks of fcc nickel appear, showing the transformation from hcp phase to fcc phase,(4) The catalysis of as-synthesized Cu nanoparticles on thermal decomposition of AP was investigated by TG-DSC. The results show that, Cu nanoparticles have obvious catalysis on the thermal decomposition of AP.