Study On Synthesis Of Gold Nanoparticles And Their Self-Assembled Films On The Surface Of Electrode

This thesis mainly focused on the synthesis of gold nanoparticles. Well dispersed gold nanoparticles and those with special shapes were synthesized through electrochemical and thermochemical methods. TEM, HRTEM, UV-Vis, IR, SEM, XRD were employed to characterize the synthesized nanoparticles. Attempts were made to assemble the gold nanoparticles to the iron surfaces. And electrochemistry measurements such as EIS, polarization curves were used to characterize the assembled films. The main research results are as following:1. Well dispersed gold nanoparticles were synthesized in aqueous solution through electrochemical reduction under the protection of PVP. The absorption plasma of the result solution centered at 520nm after the reaction, demonstrating the formation of gold nanoparticles. The effects of reaction time and AuCl₄^2- concentration on the formation of the Au nanoparticles were studied. The protection mechanism of PVP during the Au nanoparticles formation was also discussed. TEM, IR, UV-Vis were used to characterize the products. Results indicated that PVP plays an important role in the formation of gold nanoparticles. Well-dispersed Au nanoparticles were obtained when the concentration of PVP was increased.2. In the second part of this thesis, We demonstrates a one-step thermal process route to the synthesis of non-spherical gold colloids. By regulating the concentrations of PVP and HAuCl₄ or the reductants, various shapes of gold nanoparticles including the shapes of triangular, dodecahedron, aubergine, and network nanocrystals were obtained. The products were well dispersed and the HRTEM images of the triangular Au nanoparticles presented clear lattice fringes with the interfringe distance measured to be 0.23nm, which well corresponds to the lattice spacing of the {111} plane.The reduction kinetics of HAuCl₄ by the hydroxyl end group of PVP was discussed.3. We find that those gold nanocrystals with unique geometrical shapes have a strong tendency to be immobilized spontaneously on the ITO glass substrate. SEM was employed to characterize the film. Attempts were made to assemble the gold nanoparticles to the iron surfaces. And electrochemistry measurements such as EIS, polarization curves were used to characterize the assembled films. The inhibition efficiency of this film for iron in 0.5 mol·dm^-3 H₂SO₄ solutions were 68.8% respectively after two hours immersing time.