碳量子点及其复合材料的制备与光学性能研究

发布时间：2018-05-13 12:22

本文选题：碳量子点 + 荧光　；参考：《北京化工大学》2017年博士论文

【摘要】：碳量子点(Carbon dots or CQDs)是继石墨烯、碳纳米管、富勒烯后,新出现的一种碳纳米材料,其粒径尺寸一般小于10 nm,具有很强的量子限域效应。由于其制备方法简单,合成成本低,制备出的碳量子点光学稳定性好,毒性低,易于表面功能化,所以在很多领域都受到了广泛关注。但目前碳量子点仍然存在一些急需解决的问题:(1)产量低碳量子点的产量一般为毫克级,无法大规模生产;(2)应用范围窄碳量子点的应用主要基于单个粒子或在水相中的应用;(3)磷光研究少目前对碳量子点光学性能的研究主要集中在荧光方面。本论文针对目前碳量子点所存在的一些问题,通过选择和优化合成策略,获得了不同性能的荧光碳量子点。另外,还将合成的碳量子点复合到了各种基质中,制备了荧光/磷光双发射的碳量子点基复合材料。具体内容,主要分为以下三个部分:在第二章中,我们以异氟尔酮二异氰酸酯(IPDI)为单一碳源,微波辐射法制备了氮掺杂的碳量子点(N-doped CQDs)。该合成方法简单、高效,而且未使用有机溶剂,绿色环保。更重要的是,我们的合成产率高达83%,克服了目前碳量子点由于产率低,无法用于大规模生产的缺陷。另外,我们还通过傅里叶红外光谱法研究了碳量子点的形成机理,在反应过程中异氰酸酯首先发生自聚,形成碳化二亚胺、二聚体和多聚体结构,在高温下碳化二亚胺结构分解,然后通过成核、裂变形成碳量子点。合成的N-doped CQDs为油溶性的,可以稳定的分散于各种常见的有机溶剂和单体中。我们利用“monomer as solvent”的方法,将碳量子点原位分散到IPDI单体中,合成了碳点/聚氨酯复合材料。令人惊奇的是,合成的复合材料不仅在紫外光下发蓝色荧光,而且在紫外灯熄灭后室温下还有肉眼可见的余辉现象。该磷光主要来源于碳量子点表面芳香羰基的激发三线态,同时基质与碳量子点之间形成的氢键和基质本身的刚性,减少了激发三线态的非辐射跃迁。另外,复合材料的磷光还对氧气具有一定的响应性,可以用于氧气传感。第三章中,针对第二章制备的油溶性碳量子点不能用于水相的问题,我们以第二章合成的N-doped CQDs为原料,一步水热法制备了两亲性碳量子点(ACDs)。该合成方法简单、温和,无需表面钝化剂或强酸、强碱处理。制备的ACDs在水中可以稳定的存在,光学稳定性好,抗光漂白性强,在pH=4～11范围内荧光强度不变。ACDs对三价铁离子具有很好的响应性,检测范围宽(0～200 mM),最低检测限为1.62 mM。另外,ACDs细胞毒性低,具有荧光上转换特性,被成功的用于单/双光子细胞成像。利用ACDs的双亲性特性,我们还将ACDs原位复合到了 PU和PVA基质中,制备的复合材料既发荧光又发磷光。而且ACD/PVA复合材料的磷光寿命长达450 ms,实现了两亲性碳量子点在磷光材料中的应用。第四章中,我们报道了一种新的碳量子点基室温磷光材料,并且提出了碳量子点磷光调控的新策略。该策略主要是将碳量子点分散到三聚氰酸钠中,通过调节体系pH值来实现磷光的可控。基质和碳量子点之间形成的氢键,可以有效的固定磷光发色基团(C=O)。当体系pH=11.5时,碳量子点基室温磷光材料的磷光寿命长达700毫秒,磷光效率高达15%。据我们所知,这是目前报道的磷光寿命最长,效率最高的碳量子点基室温磷光材料。实验结果证明,磷光性能的可控主要归因于碳量子点本身独特的pH响应性。碳量子点表面羧基的去质子化,更有利于荧光和磷光的发射。此外,基于稳定有效的荧光/磷光双发射特性,我们的复合材料可以用于构建新型的化学传感器和LED。
[Abstract]:Carbon quantum dots (Carbon dots or CQDs) are a new kind of carbon nanomaterials, following graphene, carbon nanotubes and fullerenes. The size of the carbon quantum dots is generally less than 10 nm and has a strong quantum confinement effect. Because of its simple preparation method and low synthesis cost, the prepared carbon quantum dots have good optical stability, low toxicity and easy surface functionalization. There are still a lot of attention in many fields, but there are still some urgent problems to be solved at present: (1) the yield of low carbon quantum dots is generally milligram and can not be produced in a large scale; (2) the application of narrow carbon quantum dots in the application range is mainly based on single particles or in the water phase; (3) the study of phosphorescence is less than the amount of carbon. The research on the optical properties of the sub points is mainly focused on the fluorescence. In this paper, the fluorescent carbon quantum dots with different properties have been obtained by selecting and optimizing the synthesis strategies for the problems of carbon quantum dots. In addition, the carbon quantum dots are combined into various substrates, and the carbon quantum dots with double emission of fluorescence / phosphor are prepared. The specific content is divided into three parts: in the second chapter, we use isoflopone diisocyanate (IPDI) as a single carbon source and microwave radiation method to prepare nitrogen doped carbon quantum dots (N-doped CQDs). The synthesis method is simple, efficient, and unused organic solvents, green environmental protection. More importantly, our synthesis The yield is up to 83%, which overcomes the defect that the carbon quantum dots can not be used for large-scale production because of the low yield of carbon quantum dots. In addition, we have also studied the formation mechanism of carbon quantum dots by Fourier transform infrared spectroscopy. In the process of reaction, the isocyanate was first self polymerized, formed a carbonated two imide, two polymer and polymer structure, and carbonized two at high temperature. The imine structure is decomposed and then formed by nucleation and fission to form a carbon quantum dot. The synthesized N-doped CQDs is oil soluble and can be dispersed in a variety of common organic solvents and monomers. We use the "monomer as solvent" method to disperse the carbon quantum dots in the IPDI monomer in situ, and make a carbon point / polyurethane composite. It is surprising that the composite material not only sends blue fluorescence in the ultraviolet light, but also has the visible afterglow of the naked eye at room temperature after the UV lamp is extinguished. The phosphorescence mainly comes from the three wire excited state of aromatic carbonyl groups on the surface of the carbon quantum dots, and the hydrogen bond and the matrix itself, formed between the matrix and the carbon quantum dots, reduce the excitation. In addition, the phosphorescence of the composite has a certain responsiveness to oxygen and can be used in oxygen sensing. In the third chapter, the oil soluble carbon quantum dots prepared in the second chapter can not be used in the water phase. We use the N-doped CQDs synthesized in the second chapter as the raw material, and the two parent carbon quantum is prepared by one step hydrothermal method. Point (ACDs). The synthetic method is simple, mild, without the need of surface passivating agent or strong acid, strong alkali treatment. The prepared ACDs can be stable in water, good optical stability, strong photobleaching resistance. In the range of pH=4 ~ 11, the fluorescence intensity constant.ACDs has good response to trivalent iron ions, the detection range is wide (0~200 mM), the minimum detection limit is 1 .62 mM., in addition to the low toxicity of ACDs cells, has a fluorescence upconversion characteristic, and has been successfully used for single / two-photon cell imaging. Using the parental properties of ACDs, we also compound ACDs in situ into the PU and PVA matrices with both phosphor and phosphorescence. Moreover, the phosphor life of ACD/ PVA composite material is up to 450 ms, realizing two. The application of Pro carbon quantum dots in phosphor materials. In the fourth chapter, we reported a new carbon quantum dot based room temperature phosphorescent material, and proposed a new strategy for the phosphorescence regulation of carbon quantum dots. This strategy is mainly to disperse the carbon quantum dots into sodium cyanate, and to control the phosphorescence by adjusting the pH value of the body system. The hydrogen bond formed between the points can effectively fix the phosphorescent chromophore (C=O). When the system is pH=11.5, the phosphor lifetime of the carbon quantum dots based room temperature phosphor is up to 700 milliseconds. The phosphorescence efficiency is up to 15%. as far as we know, this is the longest and most efficient phosphor base room temperature phosphorescent material which has been reported at present. The experimental results have proved that The controllability of the phosphorescence properties is mainly attributable to the unique pH responsiveness of the carbon quantum dots themselves. The deprotonation of the carboxyl groups on the surface of the carbon quantum dots is more conducive to the emission of fluorescence and phosphorescence. Furthermore, based on the stable and effective fluorescence / phosphorescent double emission characteristics, our composites can be used to construct new chemical sensors and LED..

【学位授予单位】：北京化工大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ127.11;TB33

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