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    题名: 利用掃描式電子穿隧顯微鏡觀察 修飾於鉑(111)/金(111)電極表面的聚乙二醇和對鍍鈷的影響;See all › 12 ReferencesShare Access full-text In situ STM imaging of polyethylene glycol adsorbed on an Au(111) electrode in pH3
    作者: 李來漢;Li,Lai-Han
    贡献者: 化學學系
    关键词: 聚乙二醇;鉑(111)/金(111);;掃描式電子穿隧顯微鏡;Polyethylene glycol (PEG) adsorbed on Au(111) in pH 3 sulfate media is imaged by STM.;PEG6000 admolecules appear as winding linear segments spanning ~ 40 nm.;A smooth PEG film completely covers the Au(111) electrode before hydrogen evolves;PEG film dissolves and leaves a high density of clusters on Au(111) at positive potential.;In situ STM;Polyethylene glycol
    日期: 2016-07-29
    上传时间: 2016-10-13 12:46:34 (UTC+8)
    出版者: 國立中央大學
    摘要: 利用掃描式電子穿隧顯微鏡(in situ scanning tunneling microscopy,STM)和循環伏安法(cyclic voltammetry,CV)研究金(111)及鉑(111)電極上聚乙二醇(PEG)的吸附結構,以及PEG對鈷沉積於金/鉑(111)電極的影響。在pH3 H2SO4 + 0.1 mM PEG 6000溶液中,在0.25 V時,金(111)表面形成(3  22)重排的結構,高解像掃描確認電極表面沒有吸附分子或離子,但將電位調降至- 0.2 V時,金(111)電極上出現整齊的(2 × 2√3)吸附結構,這個高規則的結構無聚乙二醇的鏈狀特徵,因此推斷是PEG樣品內汙染物,此小分子吸附導致在循環伏安圖中在- 0.35 V有一對很尖的波峰。持續將電位降至- 0.4 V時,STM顯示長鏈狀的吸附特徵,這是PEG的分子,此過程導致在- 0.38 V 有一尖銳的波峰,此為緩慢的反應,吸附一層PEG大約需要十分鐘。PEG 6000分子長度在STM中測量為大約30奈米,推論可能是以螺旋結構吸附。
    但因為pH3產氫訊號,無法觀察到這一個PEAK,所以PEG分子吸附的PEAK我們是使用了pH7 的中性溶液才得以觀察的到,而在0.7 V的PEAK是由於硫酸根取代PEG 6000伴隨著金結構轉換所造成的,那如果在含有PEG 6000的溶液中在加入氯,原本的氯的PEAK變得較寬,推測是PEG分子的存在,使得原本氯這種快速的反應轉變成較為緩慢的反應。
    而金(111)電極在pH3硫酸溶液中添加10 mM KCl在加入不同分子量的PEG發現,如果添加PEG,鈷沉積的量就會明顯的減少,如果在配合氯化鉀的添加,鈷的沉積量將會更少。說明了PEG有抑制鈷的沉積效果,但效果和分子量大小無特別關係,在STM的部分,使用的是金(111)電極在pH3硫酸中加入0.1 mM PEG 6000和10 mM CoSO4 ,不論是在0.6 V、0.35 V和0.05 V都可以看到金電極的表面沒有任何分子的吸附,但只要把電位向負調到- 0.1~ - 0.2 V,便可以看到小分子的吸附, CV圖可以看到在負電位- 0.4 V的一對很尖的PEAK,清楚的知道是一個很快的表面反應,應該是小分子的吸附,如果電位hold在- 0.1 V許久或是調至- 0.2 V或- 0.3 V,PEG會開始吸附,表面由小分子結構變成PEG 呈現線條狀,緊接著PEG會將整個電極表面都滿滿的覆蓋,而PEG高度大約為0.2~1.2 Å ,表面可以看出是稍微粗糙的,這時如果將電位往正調,直到0.7 V以上時,可以清楚的看到PEG會被硫酸根所取代,導致PEG剝落,而在STM中可以觀察到添加PEG鍍鈷部分,清楚的看到PEG會把鈷的沉積位置給佔走,讓鈷無法沉積在金(111)表面。
    ;Polyethylene glycol (PEG) together with chloride is known to suppress copper electrodeposition, which is of critical importance in the current process of Cu electroplating. The adsorption of PEG at electrified interfaces of Cu, Ag, and Au has been studied with a variety of techniques, including Raman spectroscopy, quartz microbalance, ellipsometry. It is known that the aforementioned suppressing can arise from the formation of a stable PEG-Cu+-chloride complex during Cu deposition, which holds back the reduction reaction of Cu+. Moreover, the adsorption of PEGs depends greatly on the presence of chloride and electrode potential
    In situ scanning tunneling microscopy (STM) has been used to examine the electrified interface of Au (111) and Pt (111) immersed in pH3 sulfate media containing polyethylene glycol (PEG) with average molecular weights ranging from 400 to 8000. In line with the cyclic voltammetric results showing two sharp peaks at -0.35 and -0.38 V (vs. reversible hydrogen electrode), in situ STM imaging reveals a highly ordered (2  23)rect structure at -0.38 V, ascribed to organic molecules made of carbon and oxygen present in the commercial PEG sample. Adsorption of linear PEG6000 molecules becomes evident at -0.4 V, as STM imaging discerns aggregated linear segments spanning about 27 nm long. PEG6000 islands grow with time and eventually coalesced into a uniform film cloaking the reconstructed Au(111) substrate. Switching the potential from -0.4 to E 0.7 V (or more positive values) results in dissolution of the PEG film, leaving behind a high density of clusters.
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