Preparation Of The Morphology Of Nano-silver And Its Controllability

Nanoscaled silver have received considerable attention due to their unique chemical and physical properties, and have widely potential applications in catalyst, optics, electronics, surface-enhanced Raman scattering (SERS), biomedicine, and biological sensing. These peculiar and fascinating properties of nanomaterials strongly depend on the size and the shape of the nanoparticles. Thereby morphology-controlled preparation of nanomaterials is very important and significative. Nowadays a great variety of methods have been used to obtain metal nanostructures, the shape-controllable synthesis is still a challenge for materials researchers, and finding a new synthesis method for the preparation of adjustable size and morphology of the silver nanostruetures has very important significance and broad application prospects. Based on the development of metallic silver nanoparticles in the world, in this paper, we sucsessfuly synthesized zero-dimensional spheric silver nanoparticles, one-dimensional silver nanowires and two-dimensional flower-like silver nanoplate micro-assemblies by hydrothermal route. The obtained silver products were characterized and tested, and the growth mechanism of former silver naostructures was dicussed. this dissertation presents a facile chemical solution-method to prepare silver nanoparticles with various morphologies and obtain novel silver nanostructures.Colloidal silver nanoparticles were prepared by decomposing silver carbonate with hydrothermal method in the presence of polyvinyl pyrrolidone as protecting agents and without any reducing agent. By changing the reaction temperature, time, surfactants concentration, category and the reagents concentration, silver nanoparticles were obtained and investigated by the XRD (X-ray diffraction), SEM (scanning electron microscope) and EDS (energy-dispersive spectroscopy). The optimum preparation conditions was 180℃,5 h, 0.1mol/L AgNO3,0.05mol/L NaHCO3 and 1.7 g PVP(polyvinyl pyrrolidone), and under this condition, the results show that the nanometer silver powder were spherical shape, single dispersion and about 40 nm in particle size with a narrow size distribution.We have prepared large scale silver nanowires with lengths of several hundred micrometers by using glucose as reducing agent, PVP as crystal growth control agent at 180℃for 3 h, and Fe3+ as etching agents under hydrothermal process. The influential factors such as reaction temperature, reaction time, and concentration of the reagents were studied. The diameter of synthesized silver nanowires changed from 90 nm to 300 nm with the increase of Fe3+. The results showed that the concentration of Fe3+ and PVP is the key role for controllable size and morphology for silver nanowires.We demonstrated the fabrication of the novel flower-like silver nanoplate micro-assemblies in high yields by a facile hydrothermal method. This nanostructure was synthesized in the presence of poly (vinyl pyrrolidone) and ascorbic acid at 150℃for 10h. The micro-assemblies with average size of 1-2μm are consisted of several uniform nanorods and show face centered cubic structure. The effects of the concentration of reactants, molar ratio of silver nitrate to ascorbic acid on the formation of the flower-like silver micro-assemblies were also presented. The results suggest that PVP with relative low concentration is favorable to synthesize the flower-like nanoplate micro-assemblies, and the shapes of the consisted particles in the micro-assemblies are largely modified by altering the concentration of PVP. Additionally, the concentrations and the molar ratio of AgNO3 to AsA are significant parameters for the formation of the flower-like silver nanoplate micro-assemblies. This novel silver structure is expected to behave fascinating properties of chemistry, physics and electronics.