Synthesis Of Nano/micro Silver Crystals And Their Optical Properties

Nanomaterials exhibit novel properties such as quantum size effect, nonlinear optical and electric properties, which are largely differing from the bulk materials. As one of the member of noble metallic nanomaterials family, silver nanoparticles can be used in antibacterial, cryogenic superconducting materials, bio-label materials, and optical materials.In this paper, novel flower-like silver nanoarchitectures were synthesized via a facile and environmentally benign route in the presence of citric acid and ascorbic acid at room temperature; Uniform Ag nanospheres with narrow size distribution were prepared via hydrothermal process and vigorous stirring, using trisodium citrate as reductant; Ag nano-plates were obtained through silver mirror reaction at room temperature. However, nano-spheres yielded by addition of PVP as a protective agent. The Ag crystallites were characterized by X-ray diffraction(XRD), Scanning electron microscopy(SEM), transmission electron microscopy(TEM) and UV-Vis spectrophotometer. The main points can be summarized as followed:(1) Novel flower-like silver nanoarchitectures were synthesized via a facile and environmentally benign route in the presence of citric acid and ascorbic acid at room temperature. The flower-like structures are composed of nano-petals of ca. 20 nm in thickness. A film-fold growth mechanism was proposed and it was in good agreement with the experimental results. UV-Vis curves indated. the a single peak centered at 1485 nm and continuous absorption occurred in NIR region. The influence of citric acid,concentration of ascorbic acid and pH of the initial mixture of solution has been investigated in detail.(2) Uniform Ag nanospheres with narrow size distribution were prepared via hydrothermal process and vigorous stirring, using trisodium citrate as reductant. UV-Vis curves indated that the concentration of trisodium citrate, concentration of silver nitrate and hydrothermal time had effects on UV-vis absorption spectra of the as-synthesized nanoparticles.(3) Ag nano-plates were obtained through silver mirror reaction while the length is about 100nm. The average diameter of micro-spheres is about 0.5μm~1.5μm ,which constructed by randomly stacked nanoplates. Ag nano-spheres were gained by using PVP as a protective agent. UV-Vis curves of the nano-spheres indicated that continuous absorption occurred at 350-750nm.The pH of the initial mixture,reducing agent and PVP play important roles in the formation of Ag nanoparticles.