煤基功能性碳量子点的合成、结构与性能研究

Carbon quantum dots (CQDs) is a new type of carbon nanomaterials with a number of novel properties such as steady fluorescence, easy functionalization, robust chemical inertness, high aqueous solubility and low toxicity, and it has drawn much attention recently due to its wide application potential in a number of fields. However, how to produce CQDs with tuned structure and properties cheaply and quickly remains a big challenge. In this proposal, coal, a kind of cheap and abundant carbon source, will be used for the first time as the carbon source to prepare CQDs. For this purpose, the top-down approaches including the chemical oxidation and the electrochemical synthesis will be adopted, with an aim of tuning the size and chemical properties of the graphite crystallites resulting from the coal, by coupling with centrifugation and dialyzing techniques to make CQDs that are free of anorphous carbon and macromolecules. The relationship between the sructure and properties of the sarting coal and the as-made fluorescent CQDs will be explored, which will help to optimize the oxidation processes that will be capable of tuning the properties, microstructures of the carbon sources and the as-made CQDs. The dependence of the quantum yield and the fluorescence lifetime of the as-made CQDs on the size, shape, monodispersing properties and the microstructure will be examined, which will reveal the mechanism governing the PL properties of the CQDs with different yet tunable emission wavelengths. The potential of the as-made CQDs as photocatalyst and photosensitizer in solar energy devices such as dye-sensitized solar cells will be explored. This propject will help shed a new light on the low cost production of high quality CQDs derived from coal and their structure-properties relationship, which will surely help to further improve the understanding of the carbon science and technology in general and the coal-based functional carbon nanomaterials in particular.

碳量子点是新近发现的一种新型纳米碳材料，具有荧光稳定性高、易官能化、低毒等优点，催生了发光纳米粒子研究的一个新材料体系。结构和性能可调变的碳量子点的廉价可控制备及其应用性能的调变是一个富有挑战性的课题。本项目提出以煤炭为碳源,采用化学氧化法和电化学法两种"由上而下"的制备方法，基于对煤炭中石墨微晶的调控策略，制备具有优异光致发光性能的煤基碳量子点；研究揭示煤基碳量子点的结构与碳源的结构和化学性质及预处理工艺条件间的规律性关系，研究并建立结构和性能可控的煤基碳量子点材料的制备技术策略；诠释煤基碳量子点的量子产率和荧光寿命与其尺寸、单分散性、微观结构及表面官能团修饰等之间的构效关系，揭示碳量子点荧光效应的本质，建立发射波长可调变的煤基碳量子点的制备新技术方法；探究煤基碳量子点在太阳能光解水和燃料敏化太阳能电池方面的应用潜力和特点。该项目的实施将丰富和发展纳米碳材料学科的内涵，有重要的学术价值。

以荧光碳量子点为代表的零维纳米材料是国内外高度重视的一类新型纳米功能材料，其低成本可控制备是当今纳米材料研究领域的前沿和热点之一。如何以廉价碳源为前驱体，实现对荧光碳量子点结构和组成的准确控制，进而调变其本征性能，对于深入理解碳量子点的结构与性质之间的构效关系，进而设计并构筑新型功能材料具有重要意义。本项目以煤炭为碳源，针对不同原料煤的结构和性质，设计了数种合理的工艺路线，制备出具有独特荧光性能的煤基碳量子点。主要研究成果如下：.1）以煤炭为碳源前驱体，采用硝酸氧化法、电化学刻蚀法及溶剂热法，成功制备出具有特殊荧光性质的煤基碳量子点，详细研究了碳源种类、煤岩结构、预炭化处理、电解液体系、溶剂热温度等工艺条件对煤基碳量子点收率、结构和性质的影响。结果表明，高煤化度的煤炭和丝质组分有利于提高煤基碳量子点的量子产率；通过控制预炭化温度，可实现煤基碳量子点平均粒径从1.9 nm到3.1 nm范围内的调控；溶剂热条件下得到的煤基碳量子点的量子产率高达47%。.2）系统研究了煤基碳量子点的荧光性质及其调控策略。发现，煤基碳量子点在高浓度条件下的会产生聚集效应，荧光光谱逐渐红移；中性环境条件下，碳量子点的荧光最强，过酸过碱都造成荧光猝灭，发射光谱随pH值增大逐渐红移；煤基碳量子点表面状态对其荧光性质影响很大，经硼氢化钠表面还原后的煤基碳量子点的量子产率从1.02%大幅增大到8.80%；用有机配体修饰.煤基碳量子点，可进一步提供煤基碳点的荧光产率，此外，还能够实现煤基碳量子点表面亲/疏水性的可控调节。.3）煤基碳量子点在电催化领域和离子检测领域表现出优异的应用潜质。由煤基碳量子点和石墨烯构筑的全碳复合物催化剂，在氧还原反应中表现出能够媲美商业Pt/C催化剂的催化活性，且具有更好的稳定性和更强的抵御甲醇穿透效应的能力；利用煤基碳量子点的特殊荧光特性，可以合成高灵敏度的荧光探针，用来检测水体中的铜离子，检测限可达2.0 nM。