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From China:Suzhou Institute of Medical Technology reveals the luminescence mechanism of carbon dots

Carbon dots (CDs) were first reported in 2004 and can be divided into carbon quantum dots (CQDs), graphene quantum dots (GQDs), carbonized polymer dots (CPDs) and carbon nanodots (CNDs). CDs are of interest because of their properties, such as high photoluminescence quantum yield (PLQY), tunable emission wavelength, good biocompatibility, and photobleaching resistance. So far, a large number of literatures have reported its applications in biological imaging, sensor analysis, cancer therapy, catalysts and so on. However, the actual fluorescence mechanism of carbon dots is still unclear, which has puzzled researchers for a long time and limited the development of carbon dots to some extent. Various fluorescence mechanisms have been reported, including quantum confined effect (QCE), quantum size effect (QSE), surface state, crosslinking enhanced emission effect (CEE) and molecular state.

Recently, Dong Wenfei, a researcher at suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, and his team studied the molecular structure and luminescence behavior of carbon dots through purification and separation, and proposed the luminescence mechanism and formation mechanism of carbon dots. In this study, o-PD CDs was isolated by column chromatography and two precise molecular fluorophore structures, 2, 3-diaminophenazine (DAP) and 2-amino-3-hydroxyphenazine (AHP), were identified. The researchers also extracted two green compounds (G-CD1 and G-CD2) and a blue compound (B-CDS). Further experiments showed that DAP was dominant in fluorescence in O-PD CDs solution, accounting for 14.1% by mass. In addition, nanoparticles with different particle sizes can be formed by adjusting DAP concentration. DAP, AHP, G-CDS and B-CDS show CPDs, amorphous points, nanocrystals, graphite sheets and reticular polymer-like structures.

Therefore, researchers believe that the carbon spots are formed by DAP, which initially aggregates into polymer clusters and then gradually carbonizes over time. As the reaction progresses further, the collapse and aromatization processes provide the CDs with a shell shape. In addition, considering the high PLQY of these components, polychromatic and white light-emitting diodes (W-leds) have been prepared, indicating that carbon dots have high application potential in LED industry. The above work revealed that the photoluminescence mechanism of o-phenylenediamine carbon points was derived from small molecules, and confirmed that the system was composed of polymolecular states, which provided guidance for the preparation of carbon points in similar systems and expanded the potential application of carbon points in LED industry.

The Formation mechanism of carbon dots: From chemical structures to fluorescent behaviors was published in Carbon. The research work was supported by the National Key RESEARCH and Development Program, the National Natural Science Foundation of China, and the Natural Science Foundation of Jiangsu Province.

Paper Link & NBSP;

Figure 1. Schematic diagram of preparation, separation and purification of carbon dots

Figure 2. Schematic diagram of carbon point formation mechanism & NBSP;

Carbon dots (CDs) were first reported in 2004 and can be divided into carbon quantum dots (CQDs), graphene quantum dots (GQDs), carbonized polymer dots (CPDs) and carbon nanodots (CNDs). CDs are of interest because of their properties, such as high photoluminescence quantum yield (PLQY), tunable emission wavelength, good biocompatibility, and photobleaching resistance. So far, a large number of literatures have reported its applications in biological imaging, sensor analysis, cancer therapy, catalysts and so on. However, the actual fluorescence mechanism of carbon dots is still unclear, which has puzzled researchers for a long time and limited the development of carbon dots to some extent. Various fluorescence mechanisms have been reported, including quantum confined effect (QCE), quantum size effect (QSE), surface state, crosslinking enhanced emission effect (CEE) and molecular state.

Recently, Dong Wenfei, a researcher at suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, and his team studied the molecular structure and luminescence behavior of carbon dots through purification and separation, and proposed the luminescence mechanism and formation mechanism of carbon dots. In this study, o-PD CDs was isolated by column chromatography and two precise molecular fluorophore structures, 2, 3-diaminophenazine (DAP) and 2-amino-3-hydroxyphenazine (AHP), were identified. The researchers also extracted two green compounds (G-CD1 and G-CD2) and a blue compound (B-CDS). Further experiments showed that DAP was dominant in fluorescence in O-PD CDs solution, accounting for 14.1% by mass. In addition, nanoparticles with different particle sizes can be formed by adjusting DAP concentration. DAP, AHP, G-CDS and B-CDS show CPDs, amorphous points, nanocrystals, graphite sheets and reticular polymer-like structures.

Therefore, researchers believe that the carbon spots are formed by DAP, which initially aggregates into polymer clusters and then gradually carbonizes over time. As the reaction progresses further, the collapse and aromatization processes provide the CDs with a shell shape. In addition, considering the high PLQY of these components, polychromatic and white light-emitting diodes (W-leds) have been prepared, indicating that carbon dots have high application potential in LED industry. The above work revealed that the photoluminescence mechanism of o-phenylenediamine carbon points was derived from small molecules, and confirmed that the system was composed of polymolecular states, which provided guidance for the preparation of carbon points in similar systems and expanded the potential application of carbon points in LED industry.

The Formation mechanism of carbon dots: From chemical structures to fluorescent behaviors was published in Carbon. The research work was supported by the National Key RESEARCH and Development Program, the National Natural Science Foundation of China, and the Natural Science Foundation of Jiangsu Province.

Paper Link & NBSP;

Figure 1. Schematic diagram of preparation, separation and purification of carbon dots

Figure 2. Schematic diagram of carbon point formation mechanism & NBSP;

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