臺灣博碩士論文加值系統

光致發光（Photoluminescence, PL）是指當價帶的電子吸收高能光子並躍遷至導帶，隨後複合回到價帶時重新發射出較低能量的光子的現象。與此相反，上轉換光致發光（Up-Conversion Photoluminescence, UCPL）是指電子吸收低能量光子並在複合過程中重新發射出高能量光子的現象。其現象在一些石墨烯量子點（Graphene Quantum Dots, GQDs）中被觀察到。本論文研究氮摻雜石墨烯量子點（Nitrogen-doped Graphene Quantum Dots, GQDs-NH2）混合聚甲基丙烯酸甲酯（Polymethyl Methacrylate, PMMA）中的光致發光機制。研究結果明確顯示，當GQDs-NH2@PMMA在700 nm光源激發下，觀察到610 nm的UCPL。其能量增益歸因於高變形能（Ed）和由高激子-聲子耦合強度引起的自陷激子（Self-Trapped Exciton, STE）狀態。此外，自由激子態（Free Exciton state）與自陷態(Self-Trapped state)之間的壁障相當小，使得在室溫下也能觀察到UCPL。

Photoluminescence (PL) occurs when an electron at valence band was excited to conduction band by absorbing a high energy photon and recombined back to valence band resulting to re-emission of photon with lower energy. On the contrary, up-conversion photoluminescence (UCPL) occurs when an electron absorbs a low energy photon and re-emit the photon with higher energy during the recombination process. This phenomenon was observed in some graphene quantum dots (GQDs). This research focuses on unraveling the photoluminescence mechanism of Nitrogen-doped Graphene quantum dots embedded in polymethyl methacrylate (GQDs-NH2@PMMA). The results clearly show that UCPL was observed at 610 nm when GQDs-NH2@PMMA was excited with 700 nm light source. The energy gain was due to high deformation energy (Ed) and metastable self-trapped exciton (STE) state which was caused by high exciton-phonon coupling strength. In addition, the barrier energy between the free exciton state and metastable self-trapped state is considerably low making the UCPL observable even at room temperature.

摘要 I
Abstract II
誌謝 III
目次 IV
圖目錄 VI
第一章 緒論 1
1.1 研究背景 1
1.2 研究動機 6
第二章 實驗介紹 9
2.1 實驗材料 9
2.2 實驗樣品製備流程 9
2.2.1 製備1,3,6-三硝基芘(1,3,6-TNP) 9
2.2.2 製備氮摻雜石墨烯量子點溶於乙酸乙酯 10
2.2.3 聚甲基丙烯酸甲酯(PMMA)和氮摻雜石墨烯量子點之固態 11
2.3 實驗系統及技術原理 12
2.3.1 穿透式電子顯微鏡 (Transmission electron microscope) 12
2.3.2 X射線光電子能譜學(X-ray photoelectron spectroscopy) 12
2.3.3 吸收光譜分析儀及吸收度 13
2.3.4 螢光發射光譜、激發光譜及螢光生命期光譜儀 15
第三章 結果與討論 21
3.1 氮摻雜石墨烯量子點的結構 21
3.1.1 穿透式電子顯微鏡(Transmission electron microscope，TEM)成像 21
3.1.2 X射線光電子能譜學(X-ray photoelectron spectroscopy，XPS) 22
3.2 GQDs-NH2-PMMA的光學特性 22
3.3 不同激發光波長的UCPL現象 27
3.4 Excitation power dependent UCPL 28
3.5 PL 的Gaussian peaks及不同發射光波長的時間解析光激螢光 30
3.6 不同溫度下的PL、UCPL變化 32
3.7 GQDs-NH2@PMMA之UCPL 發光機制模型 37
第四章 結論 39
參考文獻 40

圖目錄
圖 1-1石墨烯示意圖2 1
圖 1-2不同尺寸量子點及其螢光3 2
圖 1-3石墨烯量子點結構4 2
圖 1-4 Top-down和Bottom-up合成方法6 3
圖 1-5 Top-down和Bottom-up合成種類5 4
圖 1-6 (a)斯托克斯位移及(b)反斯托克斯位移8 5
圖 1-7斯托克斯光致螢光及上轉換光致螢光機制示意圖 6
圖 1-8激子-聲子耦合造成自陷激子示意圖10 7
圖 1-9自陷激子能階示意圖 8
圖 2-1製備1,3,6-TNP示意圖 9
圖 2-2 TNP合成DMF、HCl示意圖 10
圖 2-3 製備氮摻雜石墨烯量子點示意圖 10
圖 2-4 製備GQDs-NH2@EA示意圖 11
圖 2-5 GQDs-NH2@PMMA示意圖 11
圖 2-6 XPS能譜圖示意圖 13
圖 2-7 Shimadzu UV-2600i 13
圖 2-8光穿過樣品示意圖 14
圖 2-9 Fluotime300示意圖 15
圖 2-10 Fluotime300光路示意圖 16
圖 2-11螢光、磷光示意圖 16
圖 2-12測量時間解析光激螢光示意圖11 17
圖 2-13時間解析光激螢光示意圖 17
圖 2-14積分球(Integrating sphere) 18
圖 2-15 PLQY示意圖 19
圖 2-16低溫恆溫器 19
圖 2-17 Long pass filter 放入Fluo time 300示意圖 20
圖 3-1 GQDs-NH2@PMMA之TEM圖 21
圖 3-2 GQDs-NH2@PMMA之XPS圖。a. C1s. b. N1s 22
圖 3-3 GQDs-NH2@PMMA之a. 激發光譜 b. 螢光光譜 23
圖 3-4 GQDs-NH2@PMMA之吸收光譜 23
圖 3-5 GQDs-NH2@PMMA之Urbach energy 24
圖 3-6 GQDs-NH2@PMMA之時間解析光激螢光(TRPL) 25
圖 3-7 GQDs-NH2@PMMA之光致發光量子效率(PLQY) 26
圖 3-8 GQDs-NH2@PMMA之DCPL及UCPL現象 26
圖 3-9 GQDs-NH2@PMMA之UCPL Excitation energy dependent 27
圖 3-10 GQDs-NH2@PMMA之UCPL Excitation energy dependent趨勢圖 28
圖 3-11 GQDs-NH2@PMMA之Excitation power dependent 29
圖 3-12 GQDs-NH2@PMMA UCPL之k值及趨勢圖 29
圖 3-13 GQDs-NH2@PMMA PL之k值及趨勢圖 30
圖 3-14 GQDs-NH2@PMMA之Time-resolved emission spectrum(TRES) 31
圖 3-15 GQDs-NH2@PMMA PL之Gaussian peak 32
圖 3-16 GQDs-NH2@PMMA之 a.不同發射光波長之Time-resolved photoluminescence 和 b.不同時間下的PL光譜 32
圖 3-17 GQDs-NH2@PMMA之Temperature dependent PL 33
圖 3-18 GQDs-NH2@PMMA之Temperature dependent UCPL 34
圖 3-19 GQDs-NH2@PMMA PL之Gaussian peaks(P1、P2、P3)隨溫度變化 35
圖 3-20不同溫度下， ∆E由P3、P1的發光計算 36
圖 3-21不同溫度下， ∆E由P2、P1的發光計算 37
圖 3-22 GQDs-NH2@PMMA PL、UCPL發光機制之模型 37

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