利用同步輻射X光光電子能譜研究電漿誘導生成官能基對生物單體固定之模式

Synchrotron Radiation XPS Spectroscope Study of Functional Groups for Biomolecular Immobilization Produced by Downstream Microwave plasma

王明誠(Ming-Chen Wang)

指導教授 ： 張恆雄

中原大學/工學院/醫學工程研究所/博士(2003年)

https://doi.org/10.6840/cycu200300759

摘要

本研究利用順流式微波氮氣電漿，對排列在Au（111）、Ag（111）表面的直鏈碳及芳香環自我組裝單分子膜進行表面反應，並以同步輻射光作為高強度X光光源，配合高能量解析度之X光光電子能譜儀進行表面分析，探討電漿內的物種對於單分子膜表面的物理化學作用。再者，以電漿作用後的自我組裝單分子膜隨即與氮氣稀釋之5 %丙烯酸氣體進行氣態接枝反應，在不破壞金屬與單分子膜鍵結的情形下，使單分子膜的碳鏈末端活化位置接上羧基，以利於後續對特定生物單體接著及做為分子診斷之應用。
由於高強度同步輻射光源對自我組裝單分子膜表面可能造成結構之破壞，實驗設計中加以評估與討論。實驗結果顯示：於390 eV的光能量下，隨著掃描次數或光子密度增加，S 2p光譜表示束縛能會由S與金屬鍵結的162.0 eV逐漸位移到163.2 eV左右，說明了S與金屬的鍵結可能受到高強度同步輻射光源破壞而斷鍵。然而，只要在光通量為Ni mesh = 0.6 nA下，掃描次數低於10次以下，則直鏈碳自我組裝單分子膜不受到光源照射的影響。此結果有利於本論文所利用同步輻射光作為X光光源而進行的研究。
於電漿物理特性方面，本論文設計是要產生低離子化密度、但高自由基含量之電漿物種。利用靜電式單探針量測電漿電性參數並計算結果顯示：試片處理端的電漿密度控制在 ，換算電子溫度為0.46 ± 0.04 eV之順流式電漿。以此低離子化密度對直鏈碳及芳香環自我組裝單分子膜作用，其分析結果顯示：電漿物種可使直鏈碳自我組裝單分子膜的表面產生以C、O為主的極性基團，並使處理後的表面由疏水性轉變為親水性，推測為電漿中自由基所引起的化學作用。於相同直鏈碳鏈長下，Ag為基材的自我組裝單分子層表面抵抗此電漿破壞能力比Au為基材的表面要強；而對同質基材而言，直鏈碳鏈長愈長，其抵抗電漿破壞能力就愈強，而芳香環自我組裝單分子膜表面抵抗電漿破壞的能力又比直鏈碳要弱。另一項發現就是於單分子膜受到電漿作用後，可於被處理表面觀察到強的O 1s峰值的存在，表示低壓無氧環境中，行進的反應性電漿物種帶走管壁吸附，極低含量之氧的物種參與電漿的反應，進而成為單分子層表面新的化學組成的一部分。
使用電漿活化處理後的單分子膜與稀釋之丙烯酸氣體進行氣態接枝反應，經表面分析之結果顯示：具有含氧基團之直鏈碳與芳香環自我組裝單分子膜表面可接著丙烯酸，並測得羧基之官能基團。再於真空系統中，利用特製真空濕式反應室，在未曝於空氣環境下，將膠原蛋白與羧基作用而進行醯胺鍵結反應，固定於接著丙烯酸的表面。此結果與原本就具備功能性羧基之單分子膜固定膠原蛋白後比對，兩者在化學結構的定性上無顯著差異，表示利用電漿表面處理與之後丙烯酸氣態接枝之直鏈碳與芳香環自我組裝單分子膜可以創造出羧基官能基團，並可利用此基團成功地固定膠原蛋白。這樣的電漿形成的化學反應模式，可以進一步應用到特定生物單體或其片段的接著，將之固定於直鏈碳與芳香環自我組裝單分子膜的表面，做為具有生物功能性的外露表面並應用於分子診斷等相關的應用。

關鍵字

微波氮氣電漿 ； 自我組裝單分子膜 ； X光光電子能譜術 ； 表面改質 ； 生物分子接著

並列摘要

High-resolution photoelectron spectroscopy was applied to study the modification of alkanethiolate self-assembled monolayers (SAMs) on gold (111) and silver (111) substrates by nitrogen downstream microwave plasma. In addition to the plasma treatment, we exposed the samples to 5 vol % diluted AAc monomers (using 95 vol % high purity N2 as the carrier gas) to create the terminal O=C-OH group for the subsequent attachment of biologically relevant molecules for diagnostic to specific diseases. Because of the SAMs structure is easily destroyed by synchrotron radiation, investigation on damage effect by synchrotron radiation is necessary. Experimental result has indicated that the evolution of the S 2p spectra implies that the synchrotron radiation damage causes the transformation of the pristine binding energy 162.0 eV into 163.2 eV. To avoid X-ray-induced damage, photon flux and scan numbers should be controlled e.g. Ni mesh = 0.6 nA, scan number less then 10. The sample resulted in a low density and energy of the ionizing particles in the afterglow zone. As shown by the plasma characterization using a Langmuir probe, experimental result has indicated that current downstream plasma provides plasma density of ca. or electron temperature of ca. 0.46 eV; it is regarded as low-density plasma. Surface analyses by XPS have revealed that after low density plasma treatment, new chemical bonds such as C-N, C-O, C=O and O=C-OH are formed on the modified surface. These polarizable groups arise a hydrophilic characteristic at surface. The general character of the plasma-induced changes was found to be the same for all investigated films, independent of the substrate and alkyl chain length. The experimental data imply a higher activation barrier for the thiolate-sulfonate transformation in the case of Ag substrate as compared to Au, which suggests a stronger bonding of the thiolate species to the former substrate. At a given substrate, the length of the aliphatic chain noticeably affects the rates and desorption processes. A disordering, extensive oxidation, and partial or total desorption of alkylsulfonate moieties takes place, being mostly mediated by the oxygen radicals and reactive oxygen-derived species in plasma. The oxidation affects both alkyl matrix and the thiolate-substrate interface, where the pristine thiolate species are transformed to sulfonates (predominantly). The AAc(Acrylic Acid) monomer is then introduced through diluted and vaporized phase. We dilute vapor-phase AAc with N2, and the consistency is 5%. Such plasma-induced process is performed in a reduced pressure and the modified alkylthiols SAMs surface is characterized in ultra-high vacuum using sample transferring system. The structures of pAAc-grafted chains are reactive with activated alkyl chains, the presence of C1s at 289.5 eV (O=C-O) are regarded as the evident of coupled grafting. Subsequently, the coupling O=C-O . may react with NH2-tail proteins or enzymes and form O=C-NH bonding, eventually for specific applications such as the sensing surface as biomedical receptors.

並列關鍵字

Biomolecular Immobilization ； self-assembled monolayers ； nitrogen downstream microwave plasma ； X-ray photoelectron spectroscopy ； surface modification

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