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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/6219

    Title: 利用同步電化學掃描穿隧顯微技術研究苯胺分子在單晶Au(111)面上的吸附結構及聚合機制;Used in-situ EC-STM to study the absorption structures and electrochemical polymerization mechanism of aniline on single crystal Au (111) face
    Authors: 劉淑華;Shu-hua liu
    Contributors: 化學研究所
    Keywords: 聚苯胺;電化學掃描穿隧顯微技術;EC-STM;Poly(aniline)
    Date: 2006-06-26
    Issue Date: 2009-09-22 10:15:52 (UTC+8)
    Publisher: 國立中央大學圖書館
    Abstract: 探討電化學聚合共軛高分子的聚合條件與機制的文 章不少,因為聚合的條件會改變高分子的聚合機制進而 影響高分子的品質,但過去文章中所提的機制大部分僅 為間接推論,並未能於分子層次下進行探討聚合機制, 本研究利用掃描式穿隧電子顯微鏡(scanning tunneling microscopy, STM)技術在電化學作用下同步觀察在不同 電位下苯胺分子(ani line)在Au (111)電極表面的吸附結 構及聚合時的機制。實驗結果顯示苯胺分子在不同的電 位區間下會呈現不同的吸附結構,分別在電位為0.60V (vs RHE)時,其吸附結構為(√13 × √31),θ(覆蓋度) =0.20 及電位為0.65V (vs RHE)時,其吸附結構為(√13 × 5),θ=0.25;另外在達聚合電位(0.95V)時苯胺分子 是以頭對尾的方式聚合形成鏈狀的聚苯胺,在此同時單 晶金載體也因氧化而生成大小一致且排列整齊的奈米金 粒子。若將電位快速調到聚合電位後,再觀察單晶金電 極的表面,發現在聚合電位下,苯胺單體聚合形成聚苯胺 鏈,且呈現筆直排列狀,每條高分子的寬度約為0.7 nm 且是單層的高分子鏈,隨時間增加也觀察到第二層的聚 II 苯胺鏈形成,且當將電位由聚合電位往低電位調整時,上 一層的聚苯胺鏈會漸漸脫離吸附面,但第一層聚苯胺鏈穩固的 吸附在金(111)表面上。 The mechanism of electrochemical polymerization of conjugated polymers such as polyaniline has been well studied. Nevertheless, the proposed mechanisms were derived from the indirect evidences. As we known, so far no article has reported the polymerization mechanism derived directly from the observation of the reaction for aniline in molecular level. In this study we used in-situ EC-STM to study the absorption structures and electrochemical polymerization mechanism of aniline on single crystal Au (111) face. It was found that two absorption structures were found under different applied potentials: (√13 × √31) with θ (the surface coverage) of 0.20 was formed at the potential of 0.60V (vs RHE) and (√13 × 5) with θ of 0.25 was observed when the applied potential was raised to 0.65V (vs RHE). When the potential was raised to the polymerization potential (0.95V vs RHE) of aniline, the absorbed aniline molecules start to polymerize at the same time some Au nanoparticles which have a similar size and arranged regularly were formed. When the applied potential was raise to the polymerization potential (1.2 V vs RHE) of aniline abruptly, aniline was polymerized and absorbed on the surface of Au (111). The formed polyaniline chains contain straight and curved parts. The width of the polymer chains is about 0.7 nm and it is a monolayer coverage in the beginning but later on double-layer absorption was also observed. When the applied potential was decreased gradually, the second layer of polyaniline chains fell off but the first layer still absorbed tightly on the Au (111) electrode.
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