利用掃描式電子顯微鏡研究單一及混合硫醇分子於金(111)電極上的吸附

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/76732

Title:	利用掃描式電子顯微鏡研究單一及混合硫醇分子於金(111)電極上的吸附
Authors:	劉珮汝;Liu, Pei-Ju
Contributors:	化學學系
Keywords:	硫醇分子;掃描式電子顯微鏡;thiol;STM
Date:	2018-08-15
Issue Date:	2018-08-31 11:34:42 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究利用循環伏安法(CV)和掃描式電子穿隧顯微鏡(STM)探討單一及混合硫醇分子於金(111)上的吸附。首先，分別對MAA、MPA、MPS添加於0.1M硫酸溶液中並吸附於金(111)進行觀察。在MAA及MPA部分，尾端COOH官能基導致分子間氫鍵及兩層分子吸附於金(111)上。第一層分子以其硫端和金(ad)吸附原子及金載體形成共價鍵，吸附構型為RS-Au(ad)-SR一組，尾端之COOH朝向溶液；第二層分子藉氫鍵來和第一層分子作用。分子中間碳鏈長度不同造成分子間作用力不同，最終表面結構亦不同。相對於MAA分子，MPA分子結構較為複雜，較大的自由度導致較複雜的吸附結構。電位對兩層分子的結構有明顯的影響，特別是較負電位時，第二層分子逐漸脫附，暴露第一層的分子，可能是水合氫離子濃度增加，造成分子間氫鍵的斷裂。與單純浸泡方式製作的分子膜做比較，觀察到分子結構完全不同。在MPS部分，尾端官能基為SO3-，導致只有一層分子吸附於金(111)上，分子間的靜電斥力，造成較MPA及MAA低的覆蓋度，只有在較正電位時，MPS分子尾端帶負官能基會被電場穩定在電極上，而形成規則排列。於混合系統中，分別對MAA+MPA、MPA+MPS吸附於金(111)進行觀察。在MAA及MPA部分，相同官能基導致他們均勻混合吸附於金(111)上，形成的結構和單一分子吸附不同，吸附結構的規則度較差，在分子解析STM圖像中，兩種分子產生不同的亮點，MPA較MAA亮。表面吸附分子MPA:MAA的比例和溶液中成分不成比例，可能和分子吸附的快慢有關，MPA吸附的速率較快。MPA及MPS部分，分子混合有別於單一分子MPA或MPS的吸附結構，觀察到兩種新結構，為(√13  √21)及(3  √13)，推測分子均勻混合。於正電位0.4V觀察到(3  √13)分子結構，覆蓋度為0.21。當電位往負調於0.1V，分子結構轉變為(√13 ×√21)結構，覆蓋度為0.105。覆蓋度變低，推測部分分子脫附造成。 ;In this study,the adsorption of single and mix thiol molecules on Au(111) were investigate by cyclic voltammetry and scanning tunneling microscopy(STM). First,MAA, MPA, and MPS were separately added to a 0.1 M sulfuric acid .Both MPA and MAA molecules are adsorbed in bilayer configurations, indicating the important intermolecular interaction of hydrogen bonds via –COOH groups in these molecules. Lowering potential of Au(111) electrode results in dissolution of these bilayer structures, yielding patches of MAA and MPA monolayer directly bonded to Au(111). Molecular-resolution STM imaging is used to determine the spatial structures of these molecules. Mercaptopropanic sulfonic acid (MPS) is also examined and compared with MAA and MPA. MPS appears to be adsorbed in monolayer on Au(111). The structures seen with MPA and MPS monolayer adsorbed on Au(111) are all different, indicating that the interaction between terminal groups of these thiol molecules plays an important role in their surface organizations. In the mix system, MAA+MPA and MPA+MPS were adsorbed on Au(111). In the MAA and MPA parts, the same functional groups cause them to be uniformly mixed and adsorbed on Au (111). In the STM image, the two molecules are different. MPA is brighter than MAA. The ratio of surface adsorption molecule MPA:MAA is not proportional to the composition of the solution, which may be related to the speed of molecular adsorption, and the rate of MPA adsorption is faster. In the MPA and MPS parts, two new structures are observed, which are(√13×√21) and( 3×√13), and molecules are uniformly mixed.
Appears in Collections:	[Graduate Institute of Chemistry] Electronic Thesis & Dissertation

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