Microwave growth and tunable photoluminescence of nitrogen-doped graphene and carbon nitride quantum dots
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document.pdf
Description
Accepted version
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1.78 MB
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Author(s)
Gu, Siyong
Hsieh, Chien-Te
Ashraf Gandomi, Yasser
Chang, Jeng-Kuei
Li, Ju
Li, Jianlin
Zhang, Houan
Guo, Qing
Lau, Kah Chun
Pandey, Ravindra
Date Issued
2019
Journal
Journal of Materials Chemistry C
Publisher
Royal Society of Chemistry (RSC)
Version
Author's final manuscript
Abstract
© 2019 The Royal Society of Chemistry. Tunable photoluminescent nitrogen-doped graphene and graphitic carbon nitride (g-C3N4) quantum dots are synthesized via a facile solid-phase microwave-assisted (SPMA) technique utilizing the pyrolysis of citric acid and urea precursors. The atomic ratio, surface functionalization, and atomic structure of as-prepared quantum dots strongly depend on the ratio of citric acid to urea. The quantum dots have a homogeneous particle size and tend to form a circle and/or ellipse shape to minimize the edge free energy. The atomic ratio of surface nitrogen to carbon (N/C) in the quantum dots can reach as high as 1.74, among the highest values reported in the literature. The SPMA technique is capable of producing high-quality quantum dots with photoluminescence (PL) emission at various wavelengths on a pilot scale. The atomic structures of the N-doped graphene and g-C3N4 quantum dots are explored using molecular dynamics simulations. Increasing the urea concentration increases the tendency of in-plane N (i.e., quaternary N) substitution over that of other amino functionalizations, such as pyrrolic and pyridinic N. The PL emission can be precisely tuned via a one-step SPMA method by adjusting the precursor composition. A high quantum yield of 38.7% is achieved with N-doped graphene quantum dots, indicating the substantial influence of the N- and O-rich edge groups on the enhancement of PL efficiency. A bandgap structure is proposed to describe the interstate (π∗-π) transition of quantum dots. This work introduces a novel approach for engineering the chemical composition and atomic structure of graphene and g-C3N4 quantum dots, facilitating their research and applications in optical, electronic, and biomedical devices.
MIT Department
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
Massachusetts Institute of Technology. Department of Materials Science and Engineering
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DOI of Published Version
https://doi.org/10.1039/C9TC00233B
