| 摘要: | 本論文分成三部分，第一部分是利用循環伏安儀(cyclic voltammetry，CV)與掃描式電子穿隧顯微鏡(in situ scanning tunneling microscopy，STM)對金(111)單晶電極於含苯二酚與苯胺的硫酸中進行觀察。此部分使用的苯二酚有對苯二酚(hydroquinone，HQ)、間苯二酚(resorcinol，RS)、鄰苯二酚(catechol，CA)。在STM實驗中，加入苯二酚會在電位0.7V觀察到(√19×√21)的吸附結構，且此結構中苯胺是以z型方式沿√3方向排列，誘使此條件下的聚苯胺沿√3方向生長。除此之外，苯二酚的加入會降低聚苯胺於金(111)電極上的生長量，影響排序為RS > HQ > CT，原因可能與苯二酚於硫酸中的溶解度有關。
第二部分藉由修飾聚苯胺膜於金(111)電極表面去偵測苯二酚物種。CV實驗中觀察到三種苯二酚對聚苯胺的影響皆不同，對苯二酚使聚苯胺加速分解，間苯二酚使聚苯胺原先特徵消失，變成氧化比例高的聚苯胺，鄰苯二酚則產生1,2,4-苯三酚吸附於聚苯胺膜上，以上特色不管是在硫酸、過氯酸、鹽酸、硝酸中均可見到。雖然苯二酚會與聚苯胺互相作用，卻不會摻入聚苯胺中，另外在硫酸中修飾聚苯胺膜的金(111)電極對於對/鄰苯二酚的氧化還原電流皆有提升的效果。加入苯二酚後，STM觀察到聚苯胺有特殊網狀結構出現，三種苯二酚(HQ、RS、CA)在硫酸中造成的網狀聚苯胺分別出現在電位0.6V、0.4V、0.6V，其中藉由對/間苯二酚形成的網狀聚苯胺結構為(4×√19)與(√39×√21)。網狀結構出現的原因可能為苯二酚吸附於較稀疏的聚苯胺鏈間使其扭曲形成。
第三部分為氰化物的研究，亞鐵氰化鉀會使聚苯胺加速成長，STM觀測到金(111)電極表面苯胺吸附結構為(2√3×2√3)，並且發現其會造成金原子的移動。另外氰化鉀部分，加入電解液後會使金(111)電極表面快速變化，雖然溶液中有苯胺存在，但電位0.7V的結構為氰根離子與金原子組成的結構(2×2)，直至較正電位才觀察到苯胺的吸附。
;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. |
