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  • 學位論文

氧化石墨稀量子點的合成及其螢光特性分析

Synthesis and Optical Properties of Graphene Oxide Quantum Dots

指導教授 : 沈志霖

摘要


本論文依不同製備方式及配方成功合成出具有不同顏色之氧化石墨烯量子點,由微波合成法發現其氧化石墨烯與氫氧化鈉的混合水溶液可以合成出具有黃綠顏色之氧化石墨烯量子點,藉由水熱合成法將此配方螢光強度提升並找尋其最佳條件。透過掃描式電子顯微鏡來觀察其結構變化,也經由吸收光譜及X光射線光電子能量圖譜的實驗結果發現其氧化石墨烯隨著氫氧化鈉濃度提升其表面含氧官能基增加而具高度氧化。螢光強度隨著濃度提升分為兩部分解釋其逐漸增強與逐漸減弱之趨勢,根據實驗結果推測其發光機制,由氫氧化鈉濃度0.1 M之前,發現隨著氫氧化鈉的濃度增加,羧基(Carboxyl ; C(O)−OH)的形成也越來越多,使得輻射複合放光提升,而螢光強度提升,而濃度於0.1 M後,隨著氫氧化鈉的濃度增加,羥基(Hydroxyl ; C-OH)的形成越來越多,其抑制了輻射複合放光,導致螢光強度減弱。 本論文也利用雷射消融合成出石墨烯量子點,透過穿透式電子顯微鏡與拉曼光譜來確認其量子點之尺寸大小與結構。在溫度變化之光激螢光光譜分析中,發現螢光強度與溫度有相對應關係。我們將高斯擬合後所得隨溫度變化之螢光強度使用自捕捉極化激子理論去作解釋,而推論出氧化石墨烯之發光機制圖。而由時間解析光激螢光光譜分析,可以得到載子之生命期。藉由載子生命期隨溫度的變化下,推論在溫度達到160K之後,由於溫度上升使得載子流失,因此抑制了輻射複合效應,導致光激螢光下降。

並列摘要


In this study, graphene oxide quantum dots (GOQDs) was produced using microwave with hydrothermal treatment route and pulsed laser ablation (PLA) method. The first study includes synthesis via microwave followed by hydrothermal route, PL enhancement, and characterization of structural, compositional and optical properties of GOQDs. The second study includes synthesis via PLA method, and characterization of the optical properties of GOQDs. A yellow-green photoluminescence GOQDs was produced under microwave with hydrothermal treatment. The initial yellow-green photoluminescence GOQDs was produced via microwave treatment of graphene oxide and NaOH solution. The photoluminescence (PL) of the yellow-green photoluminescence GOQDs initially produced was enhanced by further hydrothermal treatment. The structural, compositional and optical properties of the yellow-green photoluminescence GOQDs were measured and analyzed using scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron (XPS) spectroscopy, ultra-violet visible (UV-Vis) absorption spectroscopy, and Photoluminescence (PL) spectroscopy. An excitation-dependent behavior in the yellow-green photoluminescence GOQDs was observed. We suggest that oxygen-related functional groups are responsible for the PL behavior of the yellow-green photoluminescence GOQDs. On the other hand, a blue photoluminescence GOQDs was produced via PLA method. The PL spectroscopy and time-resolved photoluminescence (TRPL) spectroscopy were used to study the steady state PL, carrier lifetime and temperature-dependent PL behavior of the blue photoluminescence GOQDs. A model based on self-trapped polaron excitons was proposed to explain the PL mechanism of the blue photoluminescence GOQDs.

參考文獻


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