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    题名: 掃描式電子穿隧顯微鏡對五環素及?吩衍生物在金(111)上的吸附結構;The structures of novel organic molecule consisting of pentacene and thiophene on Au(111)
    作者: 彭貽芬;Yi-Fen Peng
    贡献者: 化學研究所
    关键词: 五環素;有機薄膜電晶體;掃描式穿隧電子顯微鏡;OTFT;STM;pentacene
    日期: 2009-07-07
    上传时间: 2009-09-22 10:21:36 (UTC+8)
    出版者: 國立中央大學圖書館
    摘要: 利用掃描式電子穿隧顯微鏡和循環伏安法探討五環素和其衍生物在單晶金(111)和金(100)電極上的排列結構。 0.1 M過氯酸中STM分子解像圖顯示五環素吸附金(111)上的結構會隨著分子濃度( 16 – 400 μM )而有不同的排列,包括(?31 ? ?31)、(3 ? 10)、(?31 ? 10)和(?7 ? 2?7)這四種平躺的結構,結構的覆蓋度範圍從0.065 – 0.071,當五環素吸附時會提供電子給載體,因此五環素的吸附有利於重排結構的發生。在0.2 – 0.8 V(vs. RHE)的電位區間內五環素穩定吸附於電極表面,當電位小於0.2 V後溶液中的氫離子開始和五環素競爭電極上的位置,五環素離開電極表面而進入溶液中,電位大於0.8 V則重排消失,規則的五環素結構轉變為不規則,當電位又回到0.5 V後五環素重新整齊的排列在電極上,因此電位對五環素的結構變化是可逆的。增加金(111)在五環素溶液中的浸泡時間至5分鐘,五環素轉為edge-on吸附在電極上,此時五環素有側面的π-stacking作用力,形成(4Ö3 ´ Ö19)和(6 ´ Ö21)兩種結構,覆蓋度增加至0.1。金(100)由於載體表面金原子排列不同,五環素同時有平躺和垂直兩種吸附方式,平躺結構以鋸齒狀排列為(8√2 × 2√2),覆蓋度0.63,另外兩種垂直結構為(6 × 7)、(3√2 × 4√2),覆蓋度0.095和0.083。 噻吩衍生物2,6-Dibenzoyl dithieno[2,3-b:3’,2’-d]thiophene (DB-DTT)在金(111)電極上的吸附層有兩種結構(√13 × 2√19)和(9 × √3),這兩種結構不隨著溶液濃度的提高和浸泡時間的增加而有所變動。2,6-Bis(benzothiazol-2-yl) dithieno[2,3-b:3’,2’-d] thiophene (DNS-DTT)在金(111)電極上的吸附層有(15 × √3)和(12 × 2√3)兩種,DNS-DTT在載體上的分子列會朝不同方向排列,當電位從0.25 V增加至0.1 V時,DNS-DTT的結構會從表面上消失,當電位重回0.25 V後,DNS-DTT又重新吸附,重新排列後的分子結構具較少的缺陷而形成更好的吸附層。 In situ scanning tunneling microscope (STM) was used to examine the spatial structures of pentacene molecules adsorbed onto a Au(111) electrode from a benzene dosing solution containing 16 - 400 μM pentacene. Molecular-resolution STM imaging conducted in 0.1 M HClO4 revealed highly ordered pentacene structures of (?31 ? ?31), (3 ? 10), (?31 ? 10), and (?7 ? 2?7) adsorbed on the reconstructed Au(111) electrode dosed with different pentacene solutions. These pentacene structures were stable between 0.2 and 0.8 V [vs. RHE]. Increasing the potential to E > 0.8 V lifted the reconstructed Au(111) surface and disrupted the ordered pentacene adlattices simultaneously. Ordered pentacene structures could be restored by applying potentials negative enough to reinforce the reconstructed Au(111). At potentials negative of 0.2 V the adsorption of protons became increasingly important to displace adsorbed pentacene admolecules. Although the reconstructed Au(111) structure was not essential to produce ordered pentacene adlayers, it seemed to help the adsorption of pentacene molecules in a long-range ordered pattern. At room temperature (25?C), ~ one hundred pentacene molecules seen in STM images could rotate and align themselves to a neighboring domain in 10 s, suggesting that pentacene admolecules could be mobile on Au(111) under the STM imaging conditions of -150 mV in bias voltage and 1 nA in feedback current. The thiophene derivatives DB-DTT and DNS-DTT on Au(111) electrode were examined with in situ STM and CV in 0.1 M HClO4.While DB-DTT arranges in well-ordered (√13 × 2√19) and (9 × √3) structures. These two structures did not change by higher dosage.The adlayer of DNS-DTT have two well-order structures, (15 × √3) and (12 × 2√3) as coverages 0.067 and 0.042.
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