Synthesis, Formation Mechanism And Optical Properties Of Gold And Silver Nanoparticles And Nanoshells

Gold/silver nanoparticles and nanoshells exhibited unique physicochemical properties in electrics, optics, catalyzer and sensor, making them potential candidates for a wide variety of applications, such as dielectric materials, electrodes, optical labels, light-sensitive materials, biosensors and surface-enhanced Raman scattering (SERS) substrates. This dissertation reported the preparation of triangular silver, trangular gold nanoplates, spindle silver, gold and gold-silver bimetallic nanoshells by using a solution -reduction method and a seed-mediated surface growing technique, respectively. By means of characterization methods with transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Ultraviolet-Visible (UV-Vis) spectroscopy and laser Raman spectroscopy (LRS), the sizes, morphologies, structures, formation mechanism and related optical properties of these metal nanoparticles and nanoshells were investigated.A new non-light chemical method was reported to prepare triangular silver nanoplates. In the presence of polyoxyethylene (23) lauryl ether (BRIJ35) molecules, nitrate silver was reduced by sodium borohydride and sodium citrate, and the produced spherical silver nanoparticles transformed into triangular nanoplates by two growth modes at different reaction temperatures. When the solution was heated at 80℃, small triangle-like silver nanoparticles formed and then grew up into the triangular nanoplates directly. However, when the solution was heated at 60℃, small spherical silver nanparticles lined up with each other to form triangular nanoframes, and then transformed into the triangular nanoplates by filling with small silver cystals into their inners. The border size of the triangular silver nanoplates increased with the decreases in reaction temperature and effective concentration of the BRIJ35 molecules or sodium borohydride. The completeness of their triangular shape decreased as the low concentration of BRIJ35 molecules became too high or too, and the concentration of sodium borohydride increased, and meanwhile it was sensitive to the PH values of the reactive solution. The triangular silver nanoplates had three characteristic absorption...