期刊
NANOSCALE
卷 8, 期 46, 页码 19376-19382出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c6nr06447g
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资金
- NSFC [21525311, 21373045, 11404056]
- NSF of Jiangsu [BK20130016]
- SRFDP in China [20130092110029]
- Scientific Research Foundation of Graduate School of Southeast University [YBJJ1620]
- Jiangsu Innovation Projects for Graduate Student in China [KYZZ16_0117]
Nitrogen-doped graphene quantum dots (N-GQDs) hold promising application in electronics and optoelectronics because of their excellent photo-stability, tunable photoluminescence and high quantum yield. However, the absorption and emission mechanisms have been debated for years. Here, by employing time-dependent density functional theory, we demonstrate that the different N-doping types and positions give rise to different absorption and emission behaviors, which successfully addresses the inconsistency observed in different experiments. Specifically, center doping creates mid-states, rendering non-fluorescence, while edge N-doping modulates the energy levels of excited states and increases the radiation transition probability, thus enhancing fluorescence strength. More importantly, the even hybridization of frontier orbitals between edge N atoms and GQDs leads to a blue-shift of both absorption and emission spectra, while the uneven hybridization of frontier orbitals induces a red-shift. Solvent effects on N-GQDs are further explored by the conductor-like screening model and it is found that strong polarity of the solvent can cause a red-shift and enhance the intensity of both absorption and emission spectra.
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