石墨烯量子點(diǎn)的制備、表征及發(fā)光機(jī)理研究
發(fā)布時(shí)間：2019-03-21 20:09
【摘要】：近幾年,作為一種新型納米碳材料石墨烯量子點(diǎn),由于良好的水溶性、生物低毒性、穩(wěn)定而明亮的熒光等特點(diǎn),而被廣泛關(guān)注和研究。大量的制備方法不斷被提出用來合成石墨烯量子點(diǎn),并被應(yīng)用于生物成像、光電子器件、傳感器、藥物傳輸和光催化劑等領(lǐng)域。然而,石墨烯量子點(diǎn)的發(fā)光機(jī)理仍存存著很大的爭(zhēng)議,特別是本征態(tài)發(fā)光與缺陷態(tài)發(fā)光的競(jìng)爭(zhēng)或合作機(jī)制,使得石墨烯量子點(diǎn)隨著不同制備方法而展現(xiàn)出不同的發(fā)光機(jī)理。基于此,我們就如何制備獲得高晶格質(zhì)量、高量子產(chǎn)率的石墨烯量子點(diǎn)的合成方法進(jìn)行探索研究。此外,我們還對(duì)所制備的石墨烯量子點(diǎn)的發(fā)光起源進(jìn)行了深入研究。本文中,我們的主要研究成果如下:1.高質(zhì)量的石墨烯量子點(diǎn)的制備以葡萄糖、濃硫酸、去離子水為反應(yīng)物,在溫度200 oC下水熱法加熱3小時(shí),獲得具有良好晶格質(zhì)量和量子產(chǎn)率為14.3%的藍(lán)色熒光石墨烯量子點(diǎn)。結(jié)構(gòu)表征結(jié)果表明制備獲得的石墨烯量子點(diǎn)平均尺寸大小為3.35 nm和平均厚度為1 nm,是1~3層石墨烯層的盤狀結(jié)構(gòu)。光學(xué)表征結(jié)果表明該石墨烯量子點(diǎn)可發(fā)出幾乎獨(dú)立于激發(fā)波長(zhǎng)的紫色和藍(lán)色熒光。2.石墨烯量子點(diǎn)的合成機(jī)理調(diào)控實(shí)驗(yàn)中濃硫酸的使用量,發(fā)現(xiàn)合成的產(chǎn)物從無定形的低量子產(chǎn)率的綠色熒光碳點(diǎn)向晶化良好的高量子產(chǎn)率的石墨烯量子點(diǎn)轉(zhuǎn)變。通過調(diào)控反應(yīng)溫度、反應(yīng)時(shí)間和葡萄糖量來優(yōu)化實(shí)驗(yàn)條件參數(shù),獲得更高質(zhì)量的石墨烯量子點(diǎn)。分析并闡述石墨烯量子點(diǎn)合成機(jī)理,即葡萄糖先成碳核,反應(yīng)環(huán)境提供足夠能量使得碳核繼續(xù)生長(zhǎng)并去除含氧官能團(tuán),獲得尺寸更大、質(zhì)量更高的石墨烯量子點(diǎn)。3.石墨烯量子點(diǎn)的發(fā)光機(jī)理基于深入分析分析吸收譜、光致發(fā)光光譜和光致發(fā)光激發(fā)譜,認(rèn)為石墨烯量子點(diǎn)的紫外熒光和藍(lán)色熒光分別來源于C=C鍵的局域電子空穴對(duì)的復(fù)合和sp2碳域的電子躍遷。變溫光致發(fā)光光譜也進(jìn)一步證明上述結(jié)論,同時(shí)表明出石墨烯量子點(diǎn)中存在著強(qiáng)電子-電子散射和強(qiáng)電子-聲子耦合,與半導(dǎo)體量子點(diǎn)相類似的溫度特性。4.石墨烯量子點(diǎn)薄膜的良好導(dǎo)電性在拋光硅片上制備了石墨烯量子點(diǎn)薄膜,并測(cè)試了薄膜的暗電導(dǎo)和光電導(dǎo)。石墨烯量子點(diǎn)薄膜的暗電導(dǎo)約為9?S,表明石墨烯量子點(diǎn)之間存在著很強(qiáng)的電子耦合和薄膜具有良好的導(dǎo)電性;光電導(dǎo)比暗電導(dǎo)明顯增大了50%,意味著石墨烯量子點(diǎn)有望應(yīng)用在光電探測(cè)上。以上研究工作獲得了國(guó)家自然科學(xué)基金項(xiàng)目(11304197,61370042,11474201和61234005)的資助,特此感謝。
[Abstract]:In recent years, graphene quantum dots (QDs), as a new nano-carbon material, have been widely studied because of their good water solubility, low toxicity, stable and bright fluorescence and so on. A large number of preparation methods have been proposed for the synthesis of graphene quantum dots and have been used in the fields of bio-imaging, optoelectronic devices, sensors, drug transport and photocatalysts. However, the luminescence mechanism of graphene quantum dots is still controversial, especially the competition or cooperation mechanism between intrinsic state luminescence and defective state luminescence, which makes graphene quantum dots show different luminescence mechanism with different preparation methods. Based on this, we explore how to prepare graphene quantum dots with high lattice quality and high quantum yield. In addition, the origin of the photoluminescence of graphene quantum dots has been studied deeply. In this paper, our main research results are as follows: 1. High quality graphene quantum dots were prepared with glucose, concentrated sulfuric acid and deionized water as reactants, heated by hydrothermal method at 200 oC for 3 hours. Blue fluorescence graphene quantum dots with good lattice quality and 14.3% quantum yield were obtained. The results of structural characterization show that the average size and thickness of graphene quantum dots are 3.35 nm and 1 nm, respectively. They are disk-like structures with 1 / 3 layers of graphene. The optical characterization results show that the graphene quantum dot can emit purple and blue fluorescence almost independent of the excitation wavelength. 2. The synthesis mechanism of graphene quantum dots regulates the usage of concentrated sulfuric acid. It is found that the synthesized products change from amorphous green fluorescent carbon dots with low quantum yield to well crystallized graphene quantum dots with high quantum yield. Higher quality graphene quantum dots were obtained by adjusting the reaction temperature, reaction time and glucose content to optimize the experimental parameters. The synthesis mechanism of graphene quantum dots is analyzed and expounded, that is, glucose is first formed into carbon nucleus, and the reaction environment provides sufficient energy for the carbon nucleus to continue to grow and remove oxygen-containing functional groups to obtain larger size and higher quality graphene quantum dots. 3. The luminescence mechanism of graphene quantum dots is based on in-depth analysis of absorption spectra, photoluminescence spectra and photoluminescence excitation spectra. It is considered that the UV fluorescence and blue fluorescence of graphene quantum dots are derived from the recombination of local electron hole pairs of C _ (C) bond and the electron transition of sp2 carbon domain, respectively. The temperature-varying photoluminescence spectra further prove the above conclusions, and it is shown that there are strong electron-electron scattering and strong electron-phonon coupling in graphene quantum dots, which are similar to semiconductor quantum dots in temperature. 4. The results show that there are strong electron-electron scattering and strong electron-phonon coupling in graphene quantum dots. Graphene quantum dot thin films were prepared on polished silicon wafers by good conductivity of graphene quantum dot films. Dark conductivity and photoconductivity of graphene quantum dot thin films were measured. The dark conductivity of graphene quantum dot films is about 9 S, which indicates that there is strong electron coupling and good conductivity between graphene quantum dots. The apparent increase of the dark conductance by 50% means that graphene quantum dots are expected to be used in photoelectric detection. The research received funding from the National Natural Science Foundation of China (11304197,61370042, 11474201 and 61234005).
【學(xué)位授予單位】：上海交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：O471.1;O482.31
本文編號(hào)：2445277
[Abstract]:In recent years, graphene quantum dots (QDs), as a new nano-carbon material, have been widely studied because of their good water solubility, low toxicity, stable and bright fluorescence and so on. A large number of preparation methods have been proposed for the synthesis of graphene quantum dots and have been used in the fields of bio-imaging, optoelectronic devices, sensors, drug transport and photocatalysts. However, the luminescence mechanism of graphene quantum dots is still controversial, especially the competition or cooperation mechanism between intrinsic state luminescence and defective state luminescence, which makes graphene quantum dots show different luminescence mechanism with different preparation methods. Based on this, we explore how to prepare graphene quantum dots with high lattice quality and high quantum yield. In addition, the origin of the photoluminescence of graphene quantum dots has been studied deeply. In this paper, our main research results are as follows: 1. High quality graphene quantum dots were prepared with glucose, concentrated sulfuric acid and deionized water as reactants, heated by hydrothermal method at 200 oC for 3 hours. Blue fluorescence graphene quantum dots with good lattice quality and 14.3% quantum yield were obtained. The results of structural characterization show that the average size and thickness of graphene quantum dots are 3.35 nm and 1 nm, respectively. They are disk-like structures with 1 / 3 layers of graphene. The optical characterization results show that the graphene quantum dot can emit purple and blue fluorescence almost independent of the excitation wavelength. 2. The synthesis mechanism of graphene quantum dots regulates the usage of concentrated sulfuric acid. It is found that the synthesized products change from amorphous green fluorescent carbon dots with low quantum yield to well crystallized graphene quantum dots with high quantum yield. Higher quality graphene quantum dots were obtained by adjusting the reaction temperature, reaction time and glucose content to optimize the experimental parameters. The synthesis mechanism of graphene quantum dots is analyzed and expounded, that is, glucose is first formed into carbon nucleus, and the reaction environment provides sufficient energy for the carbon nucleus to continue to grow and remove oxygen-containing functional groups to obtain larger size and higher quality graphene quantum dots. 3. The luminescence mechanism of graphene quantum dots is based on in-depth analysis of absorption spectra, photoluminescence spectra and photoluminescence excitation spectra. It is considered that the UV fluorescence and blue fluorescence of graphene quantum dots are derived from the recombination of local electron hole pairs of C _ (C) bond and the electron transition of sp2 carbon domain, respectively. The temperature-varying photoluminescence spectra further prove the above conclusions, and it is shown that there are strong electron-electron scattering and strong electron-phonon coupling in graphene quantum dots, which are similar to semiconductor quantum dots in temperature. 4. The results show that there are strong electron-electron scattering and strong electron-phonon coupling in graphene quantum dots. Graphene quantum dot thin films were prepared on polished silicon wafers by good conductivity of graphene quantum dot films. Dark conductivity and photoconductivity of graphene quantum dot thin films were measured. The dark conductivity of graphene quantum dot films is about 9 S, which indicates that there is strong electron coupling and good conductivity between graphene quantum dots. The apparent increase of the dark conductance by 50% means that graphene quantum dots are expected to be used in photoelectric detection. The research received funding from the National Natural Science Foundation of China (11304197,61370042, 11474201 and 61234005).
【學(xué)位授予單位】：上海交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：O471.1;O482.31
【參考文獻(xiàn)】
相關(guān)期刊論文 前1條
1 何小芳;羅四海;曹新鑫;;納米金剛石的應(yīng)用及表面處理技術(shù)研究進(jìn)展[J];硅酸鹽通報(bào);2013年05期
，本文編號(hào)：2445277
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