胞嘧啶及鳥嘌呤於金（111）電極上吸附-陰陽離子pH值及電位控制的影響

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研究生：	吳哲愷 Che-Kai Wu
論文名稱：	胞嘧啶及鳥嘌呤於金（111）電極上吸附-陰陽離子pH值及電位控制的影響
指導教授：	姚學麟 Shueh-Lin Yau
口試委員:
學位類別：	碩士 Master
系所名稱：	理學院 - 化學學系 Department of Chemistry
論文出版年：	2021
畢業學年度：	109
語文別：	中文
論文頁數：	150
中文關鍵詞：	胞嘧啶、鳥嘌呤、金（111）、界面電化學、電位控制
相關次數：	點閱：20 下載：0
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文獻指出鳥嘌呤（Guanine, G）具有治療腫瘤的能力，經過修飾的四聚體層狀結構，會影響細胞端粒酶的複製，後續研究也指出添加高濃度的鉀離子可以使G四聚體結構更加穩定，近期對G分子的結構研究大多在超高真空系統中進行。
本研究利用電位控制掃描式穿隧電子顯微鏡（STM）觀察G分子在不同陰陽離子、pH值及電位控制下，於金電極上的吸附結構。本研究皆以Ag/AgCl參考電極為電位標示。在酸性溶液中，陰離子的共吸附會造成不同G的吸附結構。在負電位時，G分子以平躺式物理吸附在金電極上，但隨著電位越正，轉變成直立型的化學吸附。STM結果顯示在物理吸附時，G分子以平躺式的構型吸附並形成整齊的二維結構，而化學吸附時，G分子直立於金電極上形成線性結構，更正的電位會造成吸附量增加，導致線性結構的扭曲，類似指紋形狀。G分子在中性溶液的溶解度下降，只有在負電位剛添加時能夠看到結構外，在較正電位分子的吸附量增加，從單層變為多層，而表面會變得粗糙。在鹼性溶液中G的溶解度明顯提升，在負電位是無序的分子吸附，但在正電位會出現指紋狀的結構。陽離子也會和G分子共吸附，從硫酸與過氯酸中吸附時，鉀離子和G分子形成一整齊的線型結構，從分子解析的STM圖像，可以看到分子與鉀離子以1：1的比例，可能以陰陽離子對的型態共吸附在電極表面。
後續也研究胞嘧啶（Cytosine, C）分子在金上的吸附，在高真空中C分子形成無序的結構，但在有電位控制下，不同電解液中發現數種整齊的C結構。在過氯酸的中，的CV圖在C分子吸附前後圖形變化不大，僅電流有所下降， pH值得測試發現在酸性條件中，C吸附很可能為兩個分子共用一個氫離子的特殊結構。在STM觀察時，C分子會迅速在金電極上吸附形成一整齊的分子結構-（3√3 × √13），此一結構穩定存在於(0~0.4 V)的電位區間，在正電位時，吸附C分子轉換成（3√3 × √19）結構。
在了解C及G分子各別的吸附結構後，將兩者同時配置於同一溶液中觀察，藉此想探討兩分子是否會共同吸附在金電極上，也同時研究電位控制及陰離子影響。在過氯酸條件下，以1：1的比例混合均勻後添加，CV的環境下，結果與單一的G分子吸附相似，在STM的實驗中，負電位的結構和G分子無異，但在正電位載體時，分子吸附量增加而形成二層的結構，位於上層分子形成一鏈狀結構，它的長度為5-20 nm寬度約為0.7 nm，此一分子寡聚體可能是兩種分子以氫鍵結合而成，C和G在STM圖像中明顯有亮度的差異，鏈狀特徵的量和電位有關，在0.1V時形成最多分子鏈條。

Some literature pointed out that guanine (G) can be used as a drug to treat tumors. It is thought that cage-like tetramer structure of G can inhibit the replication of cell telomerase. The G tetramer has been prepared in vacuum after annealing. This is followed by more research to show that co-adsorption of potassium ions can facilitate the formation of G tetramer, which show improved structural stability. But again these studies were performed in ultra-high vacuum systems, which differ markedly from physiological condition.
In this study, a potential-controlled scanning tunneling electron microscope (STM) was used to study the adsorption structure of G molecules on the gold electrode as a function of anion and cation, pH of the media, and electrochemical potentials. In acidic solutions, the co-adsorption of anions resulted in different adsorption structures. G molecules were physically adsorbed on the gold electrode at negative potentials, but transformed to chemisorption as the potential was made more positive. The orientation of G admolecule changed from horizontal to upright and the surface coverage increased with more positive potential. This was the first stage of G adsorption, leading to ordered G adlayers on Au(111) electrode, as revealed by molecular resolution STM imaging. The second stage of G adsorption yielded crooked linear structure, having morphology similar to the shape of a fingerprint. In neutral phosphoric solutions only one ordered structure was seen at negative potential and deposition of G to give multilayer. The solubility of G in alkaline solution is significantly higher, but protracted STM imaging showed that G adlayer was disordered at negative potential, and transformed into a fingerprint-like structure at positive potential. The effect of potassium ions on G admolecules on Au(111) was examined with samples prepared by immersing in sulfuric and perchloric acids containing equal concentration G and K+. In sir STM imaging showed that G and potassium ions were co-adsorbed in an ordered structure with a 1:1 ratio. The degree of ordering deteriorated with solutions with different G/K+ ratios.
The adsorption of cytosine (C) molecule on Au(111) electrode was also examined. In contrast to disordered C structure formed in high vacuum, several C structures were found, depending on the chemical identity of the electrolyte. Aided by the CV results obtained in perchloric acid, partial deprotonation occurred at some positive potential. STM imaging revealed a (3√3 × √13)–C structure in a wide potential range, but transformed into (3√3 × √19) at more positive potential.
Finally, the co-adsorption of C and G molecules on Au(111) was investigated. The obtained STM results are used to understand the hydrogen bond formation within the adlayer potential control and anion co-adsorption. The CV recorded in perchloric acid containing1:1 C/G had the same characteristics as that of pure G. STM imaging showed that ordered structures the same as that of G molecule was formed at negative potential, but a bi-layer film was formed with the upper layer forming molecular chains 5-20 nm long and 0.7 nm wide. This structure is ascribed to mixed C and G adlayer linked by intermolecular hydrogen bonds. C and G admolecules could be differentiated by their STM intensities; C was lower than G by 0.01 nm. The mixed adlayer was most populated at 0.1V.

摘要    VII
Abstract    IX
目錄    XII
圖表目錄    XVI
第一章    緒論    1
1–1    DNA分子概述    1
1 – 1 – 1    去氧核糖核酸分子    1
1 – 1 – 2    DNA分子的發展    1
1 – 1 – 3    DNA分子特性    2
1 – 2    分子自組裝    3
1 – 2 – 1    分子間作用力    4
1 – 2 – 2    氫鍵作用力    4
1 – 2 – 3    分子吸附作用力    6
1–3 相關文獻回顧    7
1–4 研究動機    8
第二章    實驗部分    10
2–1    實驗藥品    10
2–2    實驗用氣體    11
2–3    金屬線材    11
2–4    實驗儀器設備    11
2 – 4 – 1    循環伏安儀 （Cyclic Voltammetry， CV）    11
2 – 4 – 2    循環伏安儀 （Point of Zero Charge， PZC）    11
2 – 4 – 3    掃描式穿隧電子顯微鏡（Scanning Tunneling Microscope，STM）    12
2 – 4 – 4    表面增強紅外光譜儀（Surface Enhanced Infrared Absorption Spectroscopy, SEIRAS）    13
2 – 4 – 5    研磨機（Grinder Polisher）    13
2 – 4 – 6    超音波震盪器（Ultrasonic Vibrator）    13
2–5    實驗步驟    14
2 – 5 – 1    金（111）單晶CV電極置備    14
2 – 5 – 2    金（111）單晶STM電極置備    14
2 – 5 – 3    STM分子薄膜製備    15
2 – 5 – 4    循環伏安法（CV）的前處理    16
2 – 5 – 5    掃描式穿隧電子顯微鏡（STM）的探針製備    16
2 – 5 – 6    電化學掃描式穿隧電子顯微鏡（EC-STM）的前處理    16
2 – 5 – 7    表面增強紅外光譜儀（SEIRAS）操作步驟    17
第三章    Guanine分子於Au（111）電極吸附之結果    21
3–1    電位控制對Guanine在過氯酸中吸附結構之影響    21
3 – 1 – 1    添加50 μM Guanine於0.1 M過氯酸之CV圖    21
3 – 1 – 2    添加50 μM Guanine於0.1 M過氯酸之PZC圖    23
3 – 1 – 3    添加50 μM Guanine於0.1 M過氯酸之IR光譜圖    25
3 – 1 – 4    添加1 μM Guanine於0.1 M過氯酸之STM圖    27
3 – 1 – 4    添加50 μM Guanine於0.1 M過氯酸之STM圖    30
3–2    電位控制對Guanine在硫酸中吸附結構之影響    36
3 – 2 – 1    添加50 μM Guanine於0.1 M硫酸之CV圖    36
3 – 2 – 2     添加50 μM Guanine於0.1 M硫酸之PZC圖    38
3 – 2 – 3     添加50 μM Guanine於0.1 M硫酸之STM圖    40
3–3    Guanine在磷酸緩衝溶液中吸附結構    45
3 – 3 – 1    添加50 μM Guanine於0.1 M磷酸緩衝溶液之CV圖    45
3 – 3 – 2    添加50 μM Guanine於0.1 M PBS之STM圖    47
3–4    Guanine在不同陰離子溶液中吸附結構    50
3 – 4 – 1    添加50 μM Guanine於0.1 M磷酸之CV圖    50
3 – 4 – 2    添加50 μM Guanine於0.1 M磷酸之STM圖    52
3 – 4 – 3    添加50 μM Guanine於0.1 M氫氧化鉀之CV圖    55
3 – 4 – 4    添加50 μM Guanine於0.1 M氫氧化鉀之STM圖    57
3 – 4 – 5    添加50 μM Guanine於0.1 M鹽酸之CV圖    60
3 – 4 – 6    添加50 μM Guanine於0.1 M鹽酸之STM圖    62
3–5    空氣下Guanine吸附結構在受鉀離子之影響    64
3 – 5 – 1    浸泡2 mM Guanine + 2 mM鉀離子於硫酸之CV圖    64
3 – 5 – 2    浸泡2 mM Guanine + 2 mM鉀離子於0.1 M硫酸之STM圖(0.47 V)    66
3 – 5 – 3    浸泡2 mM Guanine + 2 mM鉀離子於過氯酸之CV圖    70
3 – 5 – 4    浸泡2 mM Guanine + 2 mM鉀離子於0.1 M過氯酸之STM圖(0.47 V)    72
3–6    第三章小結    74
第四章    Cytosine分子於Au（111）電極吸附結果    77
4–1    電位控制對Cytosine在過氯酸中吸附結構之影響    77
4 – 1 – 1    添加1 mM Cytosine於0.1 M過氯酸之CV圖    77
4 – 1 – 2    添加1 mM Cytosine於pH=3及pH=6之比較CV圖    79
4 – 1 – 3    添加1 mM Cytosine於0.1 M過氯酸之PZC圖    81
4 – 1 – 4    添加1 mM Cytosine於0.1 M過氯酸之IR圖    83
4 – 1 – 5    添加1 mM Cytosine於0.1 M過氯酸之STM圖    85
4–2    電位控制對Cytosine在硫酸中吸附結構之影響    91
4 – 2 – 1    添加1 mM Cytosine於0.1 M硫酸之CV圖    91
4 – 2 – 2    添加1 mM Cytosine於0.1 M硫酸之STM圖    93
4–3    電位控制對Cytosine在鹽酸中吸附結構之影響    97
4 – 3 – 1    添加1 mM Cytosine於0.1 M鹽酸之CV圖    97
4 – 3 – 2    添加1 mM Cytosine於0.1 M鹽酸之STM圖    99
4–4    第四章小結    101
第五章    Cytosine與Guanine共沉積之結果與討論    104
5–1    電位控制對共沉積在過氯酸中吸附結構之影響    104
5 – 1 – 1    添加0.1 mM 混合溶液於0.1 M過氯酸之CV圖    104
5 – 1 – 2    添加不同比例混合溶液於0.1 M過氯酸之CV圖    107
5 – 1 – 3    添加0.1 mM 混合溶液於0.1 M過氯酸之STM圖    109
5–2    電位控制對共沉積在硫酸中吸附結構之影響    112
5 – 2 – 1    添加0.1 mM 混合溶液於0.1 M硫酸之CV圖    112
5 – 2 – 2    添加不同比例混合溶液於0.1 M硫酸之CV圖    115
5 – 2 – 3    添加0.1 mM 混合溶液於0.1 M硫酸之STM圖    117
5–3    第五章小結    124
第六章    結論    127
第七章    參考文獻    129
第八章    補充資料    131
8–1    浸泡2 mM Guanine + 2 mM鈉離子於硫酸之STM圖    131

                                

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