Controlled Synthesis, Surface Modification And SERS Of Monodisperse Gold Nanoparticles

Owing to the special optical and electrical properties, favorable biocompatibility and good catalytic activity, gold nanoparticles have extensive application prospects in fabricating nonlinear optical and microelectronic devices, catalyzing, analytical science and so on. The new preparation method and applications in spectral analysis of gold nanoparticles were studied in this dissertation. The major results of the thesis are outlined as follows:1. Controlled synthesis of gold nanoparticles:Au nanoparticles with controlled size were synthesized by the seed method. Au nanocages were synthesized by two-step polyol process. UV-visible absorption spectra and SEM were used to charaterize the Au nanoparticles and nanocages. UV-visible absorption spectra indicate that when the size of Au nanoparticles increased, peaks of the plasmon absorption spectra were broadened, accompanied with obvious red shift. Moreover, the SEM confirms the nanoparticles possess monodispersity and uniform size. UV-visible absorption spectra indicate that when more HAuCl4 was added, the cavities in Au nanocubes were larger, and the absorption peaks present red shift. SEM shows that the shape of the Au nanocages is controlled by adjusting the content of added HAuCl4.2. To solve the aggregating problem of the large size gold nanoparticles, we investigated the surface modification of the gold nanoparticles. PVP was added as protecting agents in the growth process of gold nanoparticles by seed-growth method. Results showed that PVP should be added after the synthesis, or the seed would not grow. In addition, PVP can effectively protect the gold nanoparticles against aggregation.Without PVP, the large size nanoparticles would aggregate easily.3. The toxicity of gold nanoparticles with three different shapes and different sizes to Hela and Tca 8113 cells was investigated by MTT analysis. Results indicated that the cytotoxicity on Hela cells and Tca 8113 cells was similar. At too high and too low concentration, no significant difference was observed among four different sizes. At the concentration of 4×109 particles/mL, the toxicity turned large with the size increased.4. The SERS activity of these nanoparticles was investigated in detail by using sulfhydryl pyridine as the probe molecules. SERS study shows that the potential dependent SERS intensity of sulfhydryl pyrifine as probe molecule depends greatly on the nanoparticle sizes. The 64nm nanoparticle has the highest Raman intensity and then the Raman intensity decreases in the sequence of 32nm,96nm,16nm. And PVP can increase the density of SERS.