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Engineering the excited state of graphitic carbon nitride nanostructures by covalently bonding with graphene quantum dots

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Graphitic carbon nitride (CN) materials have drawn remarkable research attention due to their extraordinary optical properties, which are especially promising for metal-free photocatalysis and photoluminescence. Herein we theoretically study the light absorption, electronic, and excitonic characteristics of covalently hybrid structures of CN quantum dots (CNQDs) and graphene quantum dots (GQDs). Density functional theory (DFT) and time-dependent DFT (TD-DFT) reveal that the relative size of CNQDs and GQDs and chemical modification to GQDs or CNQDs surface are critical determining the absorption and photocatalytic/photoluminescent performances of the as-studied structures. Importantly, the distribution position of the photoexcited electron–hole pair is found to depend on the relative size of CNQDs and GQDs, and chemical groups such as epoxy group may lead to distinct exciton distributions in the CNQD–GQD hybrid structures after attaching them to GQD or CNQD surface as compared to the case of pristine GQD and CNQD, indicating a non-negligible influence of unintended chemical reactions to CNQDs and/or GQDs under working conditions on the efficiencies of the materials for photocatalytic and photoluminescent applications.

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This work was financially supported by the Grants from Qilu University of Technology (Shandong Academy of Sciences), Colleges and Universities Twenty Terms Foundation of Jinan City (2019GXRC034), and National Natural Science Foundation of China (11874081).

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Correspondence to Ruiqin Zhang.

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Chen, S., Ullah, N. & Zhang, R. Engineering the excited state of graphitic carbon nitride nanostructures by covalently bonding with graphene quantum dots. Theor Chem Acc 139, 20 (2020). https://doi.org/10.1007/s00214-019-2525-z

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  • Carbon nitride
  • Graphene quantum dots
  • Covalent bonding
  • TD-DFT
  • Exciton distributions