| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程技術研究所 === 84 ===
The nucleation and growth of electrodeposited gold and electropolymerized pyrrole on highly oriented pyrolytic graphite (HOPG) and gold substrates were investigated via cyclic voltametry, chronoampemietry, atomic force microscopy (AFM), scanning tuimeling microscopy (STM) and lateral force microscopy (LFM). The observation of AFM indicated that many fine nuclei of gold formed on HOPG have a broad distribution in which the particle size is ca. 10-15 nm at high overpotential (E=-1.40 V vs. Ag/AgGl). It implies that the electrodeposited of gold is a progressive nucleation at high overotential. However, the larger and isolated nuclei of gold in which the particle size distribution is narrow were observed at low overpotential (E=-1.00 、 -1.20 V vs. Ag/AgCl). The particle size and height are ca. 400∼500 nm and 15∼35 nm, respectively. It demonstrated that the electrodeposition of gold is am instantaneous nucleation at low overpotential. The more charge passed, the larger particle size. If the deposition proceeds, the nuclei will merge to form a continuous film. The electropolymerization of pyrrole on gold substrate without heat treatment revealed two-dimen-sional growth, as indicated from a comparison of experimental i-t curves as well as the theoretical model. This electropolymerization was shown to proceed by an instantaneous mechanism, as observed from the morphology evolution of AFM, before nuclei combination. However, the nucleation and growth proceeded through an progressive three-dimensional mechanism. The nucleation and growth mechanism of electropolymerization on HOPG substrates is similar to that on gold substrates. For the electropolymerization on gold substrate with heat treatment, the nucleation and growth revealed an instantaneous two-dimensional mechanism before nuclei combination and an progressive three-dimensional mechanism was observed after nuclei combination. Zigzag, rod-like and helix structures were observed during nucleation, as shown by STM and AFM. The nanostructure analysis indicated that the double bond distance is ca. 1.34 A between carbon atoms and the distance is 1.434 A between carbon and nitrogen atoms in pyrrole monomer. Moreover, the configuration of pyrrole oligomer was suggested to be anti-form according to the atom resolution of AFM. On the nucleation and growth of gold on polypyrrole film, the optimum nucleation potential was found to be-1.25V vs. Ag/AgCl from the relationship between pyrrole electropolymerization charge and gold deposition overpotential. The friction force difference between gold and polypyrrole film surface could be characterized via surface morphology evolution of LFM and thus the distribution of gold on polypyrrole was observed.
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