室温长寿命磷光碳点的制备、性能调控及潜在应用研究

As a newly emerged sort of light-emitting nanomaterials in recent years, carbon dots (CDs) have attracted much attention due to holding numerous merits, such as facile preparation and surface functionalization, high photophysical and chemical stability, good water solubility and biocompatibility. Consequently, CDs have been demonstrated many potential applications including chemo-/bio-sensing, bioimaging, theranostics, and optoelectronic devices. However, the current research in the CDs-relevant field is mainly focused on the modulation of their fluorescence properties, preparation and potential applications, and the attention to their phosphorescence performance is still very limited. In view of this problem, this project intends to adopt the concept of crosslinking fluorescence enhancement, starting from the points of controlling chemical structure and doping impurity. In order to achieve CDs with highly effective long lifetime room temperature phosphorescence (RTP), the following criteria should be complied with: i) introduction of heteroatom doping and special functional groups to increase efficiency of intersystem crossing from singlet to triplet, ii) immobilization of luminogens containing in the CDs by their crossliking polymer structure, and iii) formation of hydrogen bonds in the interior of CDs to further stabilize the excited triplet species, and thus suppress the non-radiative decay process. Subsequently, we wish to clarify the conditions for producing RTP, factors for affecting RTP and structure-activity relationships of the RTP CDs by comprehensive characterizations. Finally, potential applications of the as-prepared RTP CDs will be exploited as well. Through this research, it’s expected not only to develop a new type of long lifetime RTP materials with controllable properties and provide a possible solution for the problems and limitations of the traditional RTP materials, but to offer foundations for their wide and significant applications.

作为近年来出现的一类新型纳米发光材料，碳点由于具有制备过程简单、光物理化学性能稳定、易于官能化修饰、水溶性及生物相容性好等诸多优点，在传感、医学成像/诊疗及光电器件等众多领域表现出巨大的应用潜力。然而当前该领域的研究以对其荧光性能调控、制备及应用为主，对其磷光性能的关注还非常有限。针对这个现状，本项目拟采用交联增强荧光的概念，从控制碳点结构与杂质态的角度出发，通过杂原子掺杂及特殊官能团的引入提高单重态至三重态系间窜越效率，结合交联结构对其包含发光中心的自固定及内部氢键作用稳定三重态，进而抑制非辐射衰减过程，开发高效的室温长寿命磷光碳点制备方法。通过全面表征，阐明碳点磷光产生条件、影响因素及构效关系，并探索应用潜力。通过该项目的研究，一方面有望开发出一类新型的、性能可控的室温长寿命磷光材料，为传统磷光材料存在的问题和局限提供可能的解决方案，同时为磷光材料广泛的重要实际应用奠定基础。

本项目针对碳点室温磷光的实现通常需要基质复合、余辉持续时间短、发光波长范围小等缺陷，重点研究了非复合室温长寿命磷光碳点的制备、发光中心控制与磷光波长/寿命的调控方法，并探索了碳点的功能化复合及复合体的余辉性能调控途径，以突破碳点余辉性能的限制。通过本项目的执行，获得了一系列非复合室温磷光特性的碳点、实现了多色室温磷光碳点的可控制备，并开发出了一种实现碳点长余辉发光的通用方法，制备了多种碳点长余辉发光复合体。经过深入分析研究，初步明确了碳点的生成过程及其与碳点发射性能之间的内在联系，阐明了碳化程度、杂原子元素掺杂、表面官能团交联程度等因素对碳点结构与磷光性能的调控机制。此外，还探讨了碳点与复合基质之间的复合方式及相互作用对余辉性能的重要影响，并开发出了一种制备特殊波段（UVA）碳基余辉材料的新方法，该材料可作为一种通用的复合基质，用于碳点的功能化复合，制备易于功能化、高稳定性、可分散的长余辉复合材料。最后，本项目同时支持了探索碳点在光动力治疗、药物负载与缓释、传感检测等领域的初步应用，为碳点在相关领域的后续应用研究奠定基础。通过本项目的执行，在Angew. Chem. Int. Ed.，Light: Science & Applications，Nano-Micro Lett.，Small，Mater. Chem. Front.，ACS Appl. Mater. Interfaces，Chinese. Chem. Lett.等国际著名期刊发表高水平研究论文20篇，授权或申请中国发明专利5项，圆满完成了项目设定的研究任务和目标。