|关键词||重金属离子 荧光 石墨烯量子点 二维自组装膜 扫描隧道显微镜(Stm)|
近年来，随着重金属在工农业、医药等领域的广泛应用以及人为因素引起的重金属污染事件的频发，重金属污染防治已成为世界各国关注的热点课题。重金属广泛存在于大气、土壤和水中，水体中重金属元素主要以阳离子形态存在。因此，实现水中重金属离子含量的高效、准确检测是重金属污染防治研究的重要组成部分。在诸多的检测方法中，荧光传感法作为简便、有效的一类检测方法得到了广泛关注。目前，荧光检测法主要基于溶液相中荧光探针和固定相荧光膜两种方式来实现对重金属离子的传感检测。在基于溶液相检测方法的发展中，石墨烯量子点因其毒性低、光稳定性高、比表面积大、化学惰性高及生物相容性好等优点，成为近年来的研究热点。而在基于固定相检测方法的发展中，实现固体基底上荧光分子的有序阵列化对提高传感器件的性能具有重要的意义。本论文中，我们针对以上两种检测方式进行了分别探索，系统地讨论了零维石墨烯量子点及二维石墨基分子自组装结构用于重金属离子的荧光检测，并从材料的构效关系和表界面分子水平上对它们的荧光传感行为进行了研究和揭示。本文的主要研究内容有： 一、基于溶液相的重金属离子荧光检测，本论文发展了一种自上而下的酸蒸汽切断的方法，通过限域模板的使用及对含杂原子前驱体的调控，构建了一系列新型荧光石墨烯量子点体系，并系统研究了该系列荧光量子点对Fe3+的传感性能。该方法简便、产率高、成本低，制备出的量子点水溶性好、易分离，可以实现对Fe3+的准确检测。此部分内容包括三个章节： 1、采用有序介孔二氧化硅作为纳米反应器，利用纳米空间的限域作用，通过硝酸蒸汽切断和原位过滤策略，自上而下获得了粒径可控的石墨烯量子点，产率高达48%。研究表明，该介孔二氧化硅纳米反应器可重复利用，大大降低了制备成本。以该量子点为荧光探针构筑的荧光传感器，实现了对Fe3+的快速、专一检测。进一步研究发现，当调节量子点表面的化学态后，该量子点对铜、钴、锰和镍离子也具有较好的响应，这一结果拓宽了该石墨烯量子点的应用范围。 2、使用高含氮量、大比表面的金属有机框架化合物(MOFs)导向多孔碳材料ZIF-8C为前驱体，利用独特的硝酸蒸汽策略，快速简便地获得了粒径均一、表面官能团丰富的氮掺杂石墨烯量子点。以该量子点为荧光探针构筑荧光传感器，实现了对Fe3+的灵敏、快速、专一检测，其检测限低至80 nM。这一研究也表明，通过选取适当的金属有机框架化合物导向碳材料，有望快速简易制备其它异质原子掺杂的石墨烯量子点，进一步拓宽了MOFs基材料的应用范围。 3、以含硫的多孔聚噻吩导向碳材料为前驱体，硝酸蒸汽作为剪刀和氮源同时通过简单地调节反应温度，分别获得了不同高度、粒径的蓝色和绿黄色的氮硫双掺杂的石墨烯量子点，实现了石墨烯量子点的荧光颜色调控。并将该绿黄色石墨烯量子点为荧光探针用于Fe3+的检测，线性范围较前两种量子点都宽，达到130 μM，检测限低至70 nM。这种荧光可调的双掺杂石墨烯量子点快速制备或可应用于生物成像、能源转化及发光器件等领域。 二、基于固定相的重金属离子荧光检测。我们将有机功能分子或主客体复合物通过自组装的方式固定到高定向裂解石墨(HOPG)上，形成了具有荧光性质的有序的二维组装膜，保持了原来荧光分子的荧光发射，实现了荧光探针的固定化，从而为传感器件的开发提供了基础。此部分内容分包括两个章节： 1、选取具有聚集诱导发光(AIE)性质的荧光探针分子TPE-C4-L2，将其组装在HOPG上形成二维组装膜，通过荧光技术考察引入Zn(II)前后的荧光性质的变化，同时结合扫描隧道显微镜技术(STM)技术来理解二维组装膜的结构和性质间的关系。实验结果表明正是由于金属-配体间的配位引起了二维组装膜的结构变化，减弱了自组装膜的有序性，从而导致了荧光淬灭，实现了对Zn(II)的模拟检测。2、以苯三氧十一酸(TCDB)作主体模板，选用荧光分子一芘丁酸(PBA)作客体分子，以共吸附的方式在石墨基底上构造主客体复合物，通过STM技术观察到形成了高度有序的纳米阵列膜，并利用荧光技术调查了纳米阵列膜的荧光性质。研究表明，纳米阵列膜不仅保持了PBA分子的荧光发射，且其荧光强度非常稳定，改变了PBA在溶液中氧气淬灭荧光的性质，表明其可以作为新的检测平台实现相关物质的检测。该结果为制备更稳定、高有序的荧光膜传感器提供了一定的基础。 在本论文中，在溶液相检测方面，我们使用酸蒸汽切断的方法制备的系列石墨烯量子点均实现了对Fe3+的专一性检测，并通过异质原子掺杂石墨烯量子点，提高了其对Fe3+的荧光传感性能。在固相检测方面，我们通过自组装的方式进行了石墨上荧光探针及主客体复合物的固定化，实现了对金属离子的模拟检测，或为其检测提供了可能性。总之，从石墨烯量子点的传感研究到石墨上功能分子组装膜的荧光性能考察，都揭示了材料的微观结构对其荧光性质有直接的影响。
In recent years, heavy metals have been widely used in manufacture, agriculture and pharmaceutical industry. Human activities also cause frequent occurrence of heavy metal pollution. Therefore, prevention and control of heavy metal pollution has become a worldwide topic. The heavy metals are widely distributed in atmosphere, soil and water. In water, they are mainly in the form of cation. Therefore, the efficient detection of heavy metal ions is of important in the research of the prevention and control of heavy metal contamination. Among numerous detection methods, as a simple and effective method, the fluorescence sensing has received extensive attention. At present, the fluorescent sensors are mainly based on the fluorescent probes used in solutions and embedded in on-surface films. In the development of fluorescence sensing based on solution phase, graphene quantum dots (GQDs) have become a hot research subject because they are superior in terms of low toxicity, excellent photostability, high surface area, chemical inertness and high biocompatibility. As for the fluorescence sensing based on solid phase, fabrication of the ordered array of fluorescent probes on solid substrates makes sense for improving the performance of sensing device. In this thesis, we explored the above mentioned two kinds of detection modes, respectively with systematical discussion of the possibility of application of 0D GQDs and 2D molecular self-assemblies on HOPG in the fluorescence sensing of heavy metal ions. The correlation between the structures and optical properties of materials was studied and revealed. The primary contents of the thesis are as follows:First, regarding the fluorescence detection of heavy metal ions in solution phase, we developed a facile top-down preparation of GQDs featured with acid vapour cutting process. A series of novel fluorescent GQDs have been fabricated by using confined nanoreator and precursors with heteroatoms. High-yield synthesis of GQDs with good aqueous solubility via simple, low-cost and fast separation process and utilized for accurate FL detection of Fe3+ were achieved. This section includes three chapters: 1. A low-cost top-down synthesis of GQDs using a SBA-15 template as a confined nanoreactor via a HNO3 vapor cutting and in-situ filtration strategy was presented. With the recyclable ordered mesoporous SBA-15 template enhancing the confined space at nanometer scales, a high-yield (48%) preparation and size-controllable of GQDs has been achieved. Furthermore, application of the obtained GQDs as fluorescent probes for Fe3+ determination was studied. The results showed that the obtained GQDs exhibited high selectivity towards Fe3+. The further study indicate that the fluorescence of the GQD can also be quenched by Cu2+, Co2+, Mn2+, Ni2+ after its surface modification, thus may widen the application of the obtained GQDs.2. By using a nitrogen-rich MOF-derived porous carbon (ZIF-8C) with large specific surface area as precursor, N-GQDs with uniform particle size and abundant superficial functional groups were obtained via the acid vapour cutting strategy. The obtained N-GQDs were used as a platform for the selective and rapid detection of ferric ions with a low detection limit of 80 nM. It is expected that the facile strategy presented in this study can be extended to the synthesis of GQDs doped with other heteroatoms upon an appropriate selection of initial MOF-derived carbon as raw material and also will expand the scope of application of MOF-based materials.3. Two nitrogen and sulfur co-doped GQDs (N, S-GQDs) with different particle sizes and heights were synthesized via HNO3 vapour cutting with a porous polythiophene-derived carbon via serving as the sulfur source and the HNO3 vapour presenting as the scissor and the nitrogen source. The as-prepared N, S-GQDs exhibited blue and yellow-green colored fluorescence. An application of the obtained greenish-yellow N, S-GQDs for highly selective and sensitive fluorescent detection of Fe3+ was demonstrated, with a larger linear range of 0-130 μM than the above two GQDs and a low detection limit of 70 nM. The present rapid achievement of the dual heteroatoms doped GQDs with tunable fluorescence may be applied for biomedical imaging, energy conversion, light-emitting devices and so on.Second, regarding the fluorescence detection of heavy metal ions in solid phase, we fabricated 2D fluorescent assembled film by immobilizing organic functional molecule or host-guest architecture on highly oriented pyrolytic graphite (HOPG) via self-assembly, which remain fluorescence emission of fluorescence molecule, achieving immobilizion of fluorescent probes, provide basis for development of fluorescent film sensors. This section includes three chapters: 1. The fluorescent probe TPE-C4-L2 with well known aggregation-induced emission (AIE) property was selected to fabricate 2D assembled film on HOPG. With the aid of scanning tunneling microscopy (STM), we investigated the microcosmic structure before and after the addition of Zn(II) and determined its fluorescence (FL) response to Zn(II). The correlation between their optical properties and structures at the molecular level was also revealed. The experimental results demonstrate that metal-ligand coordination is the main factor that caused the change of the SAM structures, leading to a reduced local ordering, and then results in the quenched emission of fluorescence. In this respect, we realized sensing trace amount of Zn(II).2. The luminescent molecule 1-pyrenebutanoic acid (PBA) was introduced into a host template 1,3,5-tris(10-carboxydecyloxy) benzene (TCDB) on HOPG substrate to construct a well-organized 2D nanoarray film. The structural arragment and optical property of the PBA/TCDB network on air/HOPG interface were investigated employing STM and fluorescence spectroscopy. The experimental results show that the SAM on HOPG not only can retain fluorescence emission, but also the FL intensity changed to be very stable in atmosphere condition in contrast to oxygen-induced fluorescence quenching of PBA in solution. The interesting results of such nanoarray film inspired us to explore its potential application in preparation of more stable and highly ordered films and optical devices for sensing other species in the future. In this thesis, a series of GQDs were prepared using a HNO3 vapor cutting strategy and applied for the specific fluorescence detection of Fe3+ in solution. And the fluorescent sensing properties of GQDs was improved by heteroatom doping. In the aspect of solid detection, we achieved immobilized film of fluorescent probes and host-guest complex by self-assembly and accomplished the stimulating detection or provided potential for determining metal ions. In a word, both the sensing studies on GQDs and investigations of functional molecules array on HOPG revealed that structures of materials have the direct influence on fluorescence characteristics.
|许宏波. 零维石墨烯量子点及二维石墨基组装膜用于重金属离子的荧光传感研究[D]. 北京. 中国科学院大学,2016.|
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