Yao Xiaoxiao, Wang Yinhan, Li Fangjia, Dalluge Joseph J, Orr Galya, Hernandez Rigoberto, Cui Qiang, Haynes Christy L
Department of Chemistry, University of Minnesota-Twin Cities, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, USA.
Departments of Chemistry, Chemical and Biomolecular Engineering, and Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA.
Nanoscale. 2022 Jul 7;14(26):9516-9525. doi: 10.1039/d2nr02361j.
Carbon dots (CDs) are emerging as the material of choice in a range of applications due to their excellent photoluminescence properties, ease of preparation from inexpensive precursors, and low toxicity. However, the precise nature of the mechanism for the fluorescence is still under debate, and several molecular fluorophores have been reported. In this work, a new blue fluorophore, 5-oxopyrrolidine-3-carboxylic acid, was discovered in carbon dots synthesized from the most commonly used precursors: citric acid and urea. The molecular product alone has demonstrated interesting aggregation-enhanced emission (AEE), making it unique compared to other fluorophores known to be generated in CDs. We propose that this molecular fluorophore is associated with a polymer backbone within the CDs, and its fluorescence behavior is largely dependent on intermolecular interactions with the polymers or other fluorophores. Thus, a new class of non-traditional fluorophores is now relevant to the consideration of the CD fluorescence mechanism, providing both an additional challenge to the community in resolving the mechanism and an opportunity for a greater range of CD design schemes and applications.
碳点（CDs）因其优异的光致发光性能、易于由廉价前驱体制备以及低毒性，正成为一系列应用中的首选材料。然而，荧光机制的确切本质仍在争论中，并且已经报道了几种分子荧光团。在这项工作中，在由最常用的前驱体：柠檬酸和尿素合成的碳点中发现了一种新的蓝色荧光团，5-氧代吡咯烷-3-羧酸。仅该分子产物就表现出有趣的聚集诱导发光（AEE），这使其与已知在碳点中产生的其他荧光团相比具有独特性。我们提出这种分子荧光团与碳点内的聚合物主链相关联，并且其荧光行为在很大程度上取决于与聚合物或其他荧光团的分子间相互作用。因此，一类新型的非传统荧光团现在与碳点荧光机制的考虑相关，这既给该领域解决机制带来了额外挑战，也为更广泛的碳点设计方案和应用提供了机会。
