| Summary: | 碩士 === 國立中央大學 === 化學學系 === 103 === This thesis is divided into three parts. Part I describes results of cyclic voltammetry (CV) and scanning tunneling microscopy (STM) obtained with the adsorption and oxidative polymerization of aniline on Au(111) electrode in sulfuric acid containing three isomers of benzenediol (BOH) – hydroquinone (HQ), resorcinol (RS), catechol (CA). Molecular resolution STM revealed highly ordered aniline adlattices of Au(111) - (√19 × √21) at 0.7 V with all BOHs. Aniline molecules in (√19 × √21) structure were adsorbed in zigzagged chains along the √3 direction of Au(111), which induced polyaniline to grow along the same direction. BOHs slowed down polymerization of aniline on Au(111), and the effect decreased in the order of RS > HQ > CA, due to their solubility in sulfuric acid.
Part II shows in situ STM study of the molecular structures of polyaniline (PAN) supported by Au(111) electrode when BOHs were introduced in supporting electrolyte of sulfuric acid, perchloric acid, hydrochloric acid and nitric acid. HQ would accelerate the decomposition of PAN. RS changed the electrochemical features of PAN, resulting from an increase quinone moieties in PAN molecules. CA produced 1,2,4-benzenetriol in PAN film. Although BOHs all interacted with PAN, they were not incorporated in the PANI films prepared by electrochemical means. PAN films supported by Au(111) resulted in higher currents of HQ and CA than those found with bare Au(111) in sulfuric acid. In situ STM revealed network PAN structures modified by BOHs. The potentials for formation of network structure were at 0.6, 0.4, and 0.6V for HQ, RS, and CA. The network structures identified as(4×√19) and (√39×√21) consisting of regular winding PAN chains and embedded HQ and RS via hydrogen bonds.
Part III focused on cyanide – accelerated polymerization of aniline. Potassium ferrocyanide was found to accelerate the growth of PAN, and induce the movements of gold surface. In situ STM revealed that aniline molecules were adsorbed in Au(111) - (2√3 × 2√3) structure in the presence of Fe(CN)62-, as opposed to in pure sulfuric acid. Au(111) dissolved fast in acidic solution containing CN-. In situ STM showed (2 × 2) structure of cyanide and gold atom at 0.7 V in 0.5 M H2SO4 + 0.1 mM KCN + 30 mM aniline, which transformed to uncharacterized ordered aniline structure at 0.8 V.
|
|---|
