聚合物碳点的可控合成和荧光机理研究

Photoluminescent carbon materials are new-type fluorescent materials, which have drawn increasing attention these years. This project will focus on three typical carbon materials: graphene quantum dots (GQDs), carbon nanodots (CNDs) and polymer dots (PDs), which are collectively named as carbon dots (CDs). The synthesis method of CDs was facile and efficient (the raw material is extensive); containing “bottom-up” dehydration, crosslink and carbonization of organic materials and “top-down” cutting from different carbon resource. CDs possess outstanding fluorescence, applicable photoelectric conversion ability, good biocompatibility and low toxicity, responsiveness of fluorescence quenching/enhancing, as well as chemical modification and functional integration, which make CDs wide range of applications in many fields. However, the clear photoluminescence (PL) mechanism of CDs is still open debate for the related researchers at present. Because of the variety and the “uncertain” structure of CDs, it could contain different PL mechanism for these kinds of carbon materials: the quantum confinement effect or conjugated π-domains determined by carbon core, surface state determined by hybridization of the carbon backbone and the connected chemical groups, as well as the molecule state determined by the solely fluorescent molecules connected on the surface or inner of the CDs. The present project will start with controllable synthesis of CDs. Then, the relationship between the chemical structure and PL of CDs will be investigated by model system, and the PL mechanism of the serial CDs will be explained and summarized. Finally, the clear PL mechanism of CDs will guide the high-efficiency synthesis and related novel applications.

发光碳材料作为一种新型的荧光材料，近年来已经得到人们的广泛关注。本课题主要关注三种最为典型的荧光碳材料：石墨烯量子点、碳纳米点和聚合物点（三者统称为碳点）。碳点的合成方法简单高效，原料来源广泛，包括“自下而上”有机物脱水、交联和碳化法以及各种碳源“自上而下”裂解法。碳点具有优良的发光性，可应用的光电转化能力，良好的生物相容性和低毒性，响应性的荧光淬灭/增强性质，以及易于化学修饰和功能集成性。这些优点使荧光碳点在诸多领域都有着广泛的应用。然而迄今为止，碳点的荧光机理依然是研究者争论的课题。由于碳点种类繁多、结构的“非确定性”，其可能存在多种荧光机理：碳核的量子限域效应；碳骨架和键连化学基团杂化的边缘态；碳点表面或内部存在的键连分子态。本课题将从可控合成出发，利用模型体系研究结构和发光关系，阐明系列碳点类材料的发光机理，进而指导其高效合成及新颖应用。

碳点具有优良的发光性，可应用的光电转化能力，良好的生物相容性和低毒性，响应性的荧光淬灭/增强性质，以及易于化学修饰和功能集成性。这些优点使荧光碳点在诸多领域都有着广泛的应用。本课题主要关注三种最为典型的荧光碳材料：石墨烯量子点、碳纳米点和聚合物点（三者统称为碳点）。碳点的合成方法简单高效，原料来源广泛，包括“自下而上”有机物脱水、交联和碳化法以及各种碳源“自上而下”裂解法。然而迄今为止，碳点的荧光机理依然是研究者争论的课题。由于碳点种类繁多、结构的“非确定性”，其可能存在多种荧光机理：碳核的量子限域效应；碳骨架和键连化学基团杂化的边缘态；碳点表面或内部存在的键连分子态。我们研究了石墨烯量子点（GQDs）、碳纳米点（CNDs）以及聚合物点（PDs）的荧光机理：1.碳核相关的量子尺寸效应和共轭π结构；2.碳结构和边缘基团杂化的边缘态；3.碳点表面或内部键连的分子态发光；4.交联增强发射效应。我们还实现了聚合碳点的室温磷光现象和红光碳点。具体来讲我们从可控合成出发，利用模型体系研究结构和发光关系，阐明系列碳点类材料的发光机理，进而指导其高效合成及新颖应用。我们提出了聚合物碳点的概念，探讨了它们特殊的结构，荧光发射，以及可能的荧光机理。聚合物碳点是指拥有丰富聚合物结构而且碳化程度较低的纳米粒子，它们可以通过单体或者非共轭聚合物的缩聚、交联和轻度碳化所制备的。聚合物碳点可以视为高交联度的高分子团簇或者低碳化度的碳点。聚合物碳点具有本征荧光性质，其荧光可能由以下的一种或者几种因素机制：与碳点相似的荧光机制，与非共轭荧光聚合物相似的荧光机制，CEE效应以及分子态荧光等机制。正确理解聚合物碳点的概念，避免其与碳化程度高的碳点混淆，在该领域材料的研究中具有重要意义。