【作者】 刘佳；

【导师】 高亚臣；

【作者基本信息】 黑龙江大学 ， 电子科学与技术， 2025， 博士

【摘要】 碳量子点（Carbon Quantum Dots,CQDs）是一类零维碳纳米材料,具有显著荧光性能、可调的带隙结构、无毒性和低成本等诸多优点,在荧光调控、荧光测温和发光二极管（Light-Emitting Diode,LED）领域受到了广泛关注。研究发现,基于CQDs的荧光测温在生物传感领域具有潜在的应用价值;同时,由于其荧光具有可调性,CQDs还可以应用于白光LED。然而,目前针对CQDs温度相关的荧光特性的研究还不是很系统,限制了其在更宽范围内温度测量的实际应用;另外,目前CQDs的合成过程相对较复杂,容易引入其他杂质,限制了在白光LED制备中的应用。基于此,本文旨在探索更加简单的CQDs制备方法,揭示荧光发光机制,实现荧光的调节,以推动CQDs在荧光测温和白光LED器件中的应用。具体工作内容如下:1.以石墨为前驱体,以N,N-二甲基甲酰胺为溶剂,通过溶剂热法合成了蓝绿光CQDs（G-CQDs）。在80～300 K范围内,研究了温度对G-CQDs发光特性的影响,利用阿伦尼乌斯方程和玻色子模型对发光过程进行了理论分析。结果表明,温度能够改变G-CQDs内的激子-声子的相互作用,从而导致了发光特性的变化。2.以邻苯二胺（o-Phenylenediamine,oPD）为前驱体,以乙醇为溶剂,用水热法合成了红光CQDs（R-CQDs）。以聚乙烯醇（PVA）为基质制备了柔性R-CQDs/PVA复合薄膜,研究了温度对复合薄膜发光特性的影响。结果表明,薄膜的两个发射峰荧光强度比随温度变化呈现良好的线性关系。在190～260 K范围内,测温的相对灵敏度分别达到了0.62%K^-1和0.60%K^-1,证明此薄膜也适用于低温环境下的温度测量。3.以oPD为前驱体,以乙醇为溶剂合成了CQDs,研究了浓度对发光特性的影响。发现通过调节溶剂的浓度,可以使CQDs的发射波长在540～665 nm范围内改变。为CQDs的荧光调控提供了一种简单的方法。通过形貌、组分及光谱分析,揭示了这种荧光可调的机理。进而,利用浓度调控CQDs的荧光特性,结合蓝光LED芯片,制备了颜色坐标为（0.35,0.41）,相关色温为4695 K的暖白光LED。4.以1,2,4-苯三甲酸和oPD为前驱体,以乙醇为溶剂,利用一步溶剂热法合成了白光CQDs（W-CQDs）。实验表明,该样品具有较宽的发光光谱和良好的光学稳定性。利用PVA和环氧树脂A、B胶双层封装法制备了基于紫外LED芯片的白光LED,所得白光的颜色坐标为（0.32,0.38）,色温为5656 K,展现了单一CQDs实现白光发射的新方案。综上所述,本文主要围绕CQDs的温度依赖发光、CQDs薄膜的应用和CQDs的浓度调控发光、单一CQDs白光LED应用展开研究。通过调整前驱体种类与反应条件,可以实现CQDs发光性能的可控调节。未来将重点聚焦于CQDs发光效率的提升以及在低温区域高灵敏度性能的优化,从而进一步拓展其在新型光学传感和照明器件中的应用价值。更多还原

【Abstract】 Carbon quantum dots（CQDs）are a class of zero-dimensional carbon nanomaterials with many advantages such as remarkable fluorescence performance,tunable bandgap structure,non-toxicity and low cost,which have attracted widespread attention in the fields of fluorescence modulation,fluorescence thermometry and light-emitting diode（LED）.It is found that CQDs-based fluorescence thermometry has potential applications in the field of biosensing;meanwhile,due to their fluorescence,CQDs can be also applied to white LED.However,the current research on the temperature-dependent photoluminescence（PL）properties of CQDs is not very systematic,which limits their practical application in a wider temperature range;in addition,the current synthesis process of CQDs is relatively complicated and easy introduction of other impurities,which limits their application in white LED preparation.The aim of this paper is to explore a simpler preparation method of CQDs,reveal the PL mechanism,and realize the modulation of fluorescence,so as to promote the application of CQDs in fluorescence temperature measurement and white LED devices.The specific work contents are as follows:1.Blue-green CQDs（G-CQDs）were synthesized by solvothermal method using graphite as precursor and N,N-dimethylformamide as solvent.The effect of temperature on the luminescence properties of G-CQDs was investigated in the range of 80～300 K.The luminescence process was theoretically analyzed using Arrhenius equation and Boson model.The results show that the temperature can change the exciton-phonon interaction within the G-CQDs,which leads to the PL properties.2.Red CQDs（R-CQDs）were synthesized by hydrothermal method using o-phenylenediamine（oPD）as precursor and ethanol as solvent.By mixing R-CQDs with polyvinyl alcohol（PVA）were prepared the flexible R-CQDs/PVA composite films,and the effect of temperature on the PL properties of the composite films was investigated.The results showed that the fluorescence intensity ratios of the two emission peaks of the films exhibited a good linear relationship with the temperature change.The relative sensitivities of temperature measurement in the range of 190～260 K reached 0.62%K^-1and 0.60%K^-1,respectively,proving that this film is also suitable for temperature measurement in low temperatures.3.CQDs were synthesized using oPD as precursor and ethanol as solvent,and the effect of concentration on the PL properties was investigated.It was found that the emission wavelength of CQDs could be changed in the range of 540～665 nm by adjusting the concentration of solvent.A simple method was provided for the PL modulation of CQDs.The mechanism of this luminescence tunability was revealed by morphological,component and spectra analysis.Further,warm white LEDs with color coordinates of（0.35,0.41）and an associated color temperature of 4695 K were prepared by using the concentration-tuned PL properties of CQDs in combination with blue LED chips.4.White CQDs（W-CQDs）were synthesized using one-step solvothermal method with 1,2,4-benzenetricarboxylic acid and oPD as precursors and ethanol as solvent.Experiments showed that the samples had a broad PL spectrum and good optical stability.White LEDs based on ultraviolet LED chips were prepared using the double-layer encapsulation method with PVA and epoxy resin A and B.The color coordinate of the resulting white light was（0.32,0.38）,and the color temperature was 5656 K,which provided a new idea for the preparation of white LED devices based on a single CQDs.In summary,this study mainly focuses on the temperature-dependent PL of CQDs,the application of CQDs films and the concentration-tunable emission of CQDs,and the application of single-CQDs white LED.By adjusting the precursors species and reaction conditions,the controllable tuning of the PL properties of CQDs was achieved.In the future,we will focus on improving the PL efficiency of CQDs and optimizing their high-sensitivity performance in low-temperature regions,so as to further expand their application value in novel optical sensing and LED devices.更多还原