臺灣博碩士論文加值系統

石墨烯(graphene)因為其優異的電子傳導性質，被廣泛的應用於混成催化劑(hybrid catalyst)上。石墨烯能夠有效地加強催化劑的電子傳遞速率。石墨烯和催化劑的混成比例對於催化活性有很大的影響，加入過多的石墨烯反而使得催化活性下降，而且關於石墨烯混成催化劑的電子傳導機制一直沒有一個系統性的解釋。我們以化學氣相沉積法(chemical vapor deposition)製作並得到單層的高品質石墨烯。再以層數堆疊(layer by layer stacking)的方式堆疊於光敏半導體薄膜上，製作成混成催化劑GSHF (graphene stacking hybrid film)，藉由改變GSHF上石墨烯的層數探討對有機染料的光降解反應。我們得到GSHF的光降解反應速率常數序列：3L-GSHF > 5L-GSHF > 1L-GSHF > 7L-GSHF > 金屬氧化物 (如TiO2或 ZnO)。藉由測量GSHF反應界面性質，如表面導電度、石墨烯表面能、石墨烯薄膜穿透度，我們證實了實際影響GSHF催化活性因素為石墨烯的厚度變化。利用GSHF以光催化反應於表面合成奈米金粒子(Au-GSHF)來標記在進行光催化反應時表面反應活性點的密度與數量。經由掃描式電子顯微鏡鑑定金粒子密度由高至低為：Au-3L-GSHF > Au-1L-GSHF > Au-7L-GSHF，表示反應時3L-GSHF表面光電子密度最高，但厚度達7L-GSHF時反而減少了表面的光電子密度。因此，我們推測真正的影響因素為石墨烯的能階不連續狀態，石墨烯厚度變化造成的能階不連續狀態影響了金屬氧化物上光電子電荷轉移機制。三層石墨烯能階狀態能夠使電子和電洞經由石墨烯能階快速的傳導，故3L-GSHF的反應活性會大於1L-GSHF。七層石墨烯時能階不連續的能階變多，光電子容易發生震動緩解並和電洞產生再結合反應，所以7L-GSHF反應活性低於1L-GSHF和3L-GSHF。
我們也發現以GSHF合成金奈米粒子(Au-GSHF)對於表面增強拉曼光譜上有很好的應用性，目前測量了Au-1L-GSHF、Au-3L-GSHF、Au-7L-GSHF對於染料分子R6G拉曼訊號的增強效果。透過計算增強因子(enhancement factor, EF)，Au-3L-GSHF的EF值(108)為Au-7L-GSHF(106)的100倍，而Au-1L-GSHF的EF值則為107。實驗結果以三層石墨烯為反應條件所合成的Au-GSHF有最強的表面增強訊號，此基板對於表面增強拉曼光譜能夠成為有潛力研究。

Graphene has been widely studied in hybrid nanocomposites catalyst because of its unique chemical and electrical properties. However, the enhancement mechanisms in photocatalysis of graphene hybrid catalyst with respect to the number of stacked graphene sheets have not been systematically studied before. In this work, we fabricated a graphene stacking hybrid film (GSHF) comprised of controlled number of stacked graphene layer and photoactive semiconductors (TiO2, ZnO) to investigate the variation of photocatalytic activities. Three layer graphene stacked GSHF exhibits the highest dye-degradation rate constant (k = 0.002 min-1) than other GSHF. With an order of photocatalysis rate constant：3L-GSHF > 5L-GSHF > 1L-GSHF > 7L-GHSF > TiO2 (or ZnO), we found the interface properties of conductivity; surface energy and transmittance of graphene were not the main reasons to affect the photocatalytic activities. The results show that the thickness of graphene plays an predominant role in photocatalytic performance of GSHF. To verify the thickness graphene affect, we demonstrated a photo-assisted Au deposition to label the photocatalytically active sites on GSHF surface. The FE-SEM results of Au-deposited GSHF show that 3L-GSHF has the largest Au density than 1L-GSHF and 7L-GSHF. We propose that the main reason that determines photodegradation activity is graphene energy levels quantization at different stacking thickness.
Enhancement factors of surface enhanced Raman spectra (SERS) confirm that 3L-GSHF has the largest amount of photocatalytic sites than 1L-GSHF or 7L-GSHF. We revealed that photocatalytic activities of graphene hybrid nanocomposites can be directly controlled by the thickness of graphene.

論文審定書………………………………………………………………………..i
誌謝………………………………………………………………………………..ii
中文摘要………………………………………………………………………….iv
英文摘要………………………………………………………………………….vi
第一章、緒論……………………………………………………………………..1
1.1 研究動機…………………………………………………………………….2
1.2 研究背景………………………………………………………………….....3
1.2.1 石墨烯性質介紹……………………………………………………......3
1.2.2 石墨烯合成-化學氣相沉積法與化學剝離法………………………....10
1.2.3 石墨烯厚度變化對性質的影響…………………………………….....14
1.2.4 石墨烯混成催化劑介紹…………………………………………….....17
1.2.5 光催化反應機制……………………………………………………….21
1.2.6 表面增強拉曼光譜…………………………………………….……....25
第二章、實驗樣品合成與鑑定方法…………………………………………….26
2.1 實驗藥品…………………………………………………………………....26
2.2 單層石墨烯合成……………………………………………………………27
2.2.1單層石墨烯轉移………………………………………………………..28
2.3 金屬氧化物合成…………………………………………………………....29
2.3.1 二氧化鈦薄膜合成…………………………………………………….30
2.3.2 氧化鋅薄膜合成…………………….............................................30
2.4 石墨烯混成催化劑………...……………………………………………….31
2.5 光化學合成和光降解反應研究…………………………………………....33
2.5.1 光降解反應…………………………………………………………….33
2.5.2 亞甲基藍光降解……………………………………………………….34
2.5.3 高分子聚合物染料光降解………………………………………....….34
2.5.4 不同有機染料自身光降解反應………………………………….…....34
2.5.5 光反應合成金奈米粒子………………………………………….…...35
2.5.6 氧氣電漿改變表面特性.…………………………………...………....36
2.6 實驗鑑定方法……………………………………………………………...37
2.6.1 石墨烯拉曼光譜鑑定………………………………………………....37
2.6.2 表面增強拉曼光譜量測和增強因子計算……………………...….....37
2.6.3 紫外-可見光光譜……………………………………………………...38
2.6.4 表面電阻測量………………………………………………………....39
2.6.5 表面接觸角測量……………………………………………………....40
2.6.6 掃描式電子顯微鏡…………………………………………………....41
2.6.7 低銳角X射線繞射…………………………………………………...41
2.6.8 石墨烯X射線光電子能譜…………………………………………...41
第三章、研究結果……………………………………………………….……...43
3.1 單層石墨烯的鑑定和層數堆疊實驗……………………………………...43
3.2 金屬氧化物薄膜合成和鑑定………………………………………….…..48
3.3 石墨烯混成催化劑的光催化反應…………………………………….…..54
3.4 不同石墨烯厚度GSHF表面電阻測量…………………………………...61
3.5 不同石墨烯厚度GSHF表面能對於光催化反應的影響………………...62
3.6 石墨烯厚度變化對GSHF穿透度和光催化反應的影響…………….…..69
3.7 石墨烯厚度變化對GSHF表面活性點的探討……………………….…..72
3.8 光合成之Au-GSHF表面增強拉曼光譜測量………………………….....75
第四章、實驗內容綜合討論……………………………………………….…...77
4.1 反應界面對於石墨烯混成催化劑GSHF光反應速率的影響…………...77
4.2 石墨烯厚度對於光電子傳遞速率和表面活性點的關係………………...78
4.3 石墨烯厚度對於光電子轉移機制與光反應活性的影響…………….…..80
4.4 催化劑GSHF應用於表面增強拉曼光譜測量…………………………...82
第五章、結論…………………………………………………………….……..83
參考文獻………………………………………………………………….……..84
附錄……………………………………………………………………………...85

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