Formation mechanism and optimization of highly luminescent N-doped graphene quantum dots

Photoluminescent graphene quantum dots (GQDs) have received enormous attention because of their unique chemical, electronic and optical properties. Here a series of GQDs were synthesized under hydrothermal processes in order to investigate the formation process and optical properties of N-doped GQDs...

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Bibliographic Details
Published in:Scientific reports 2014-06, Vol.4 (1), p.5294-5294, Article 5294
Main Authors: Qu, Dan, Zheng, Min, Zhang, Ligong, Zhao, Haifeng, Xie, Zhigang, Jing, Xiabin, Haddad, Raid E., Fan, Hongyou, Sun, Zaicheng
Format: Article
Language:English
Subjects:
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140/146
147/135
147/143
639/301/299/890
639/925/357/354
Carbon sources
Citric acid
Emissions
Ethylene
Graphite
Humanities and Social Sciences
multidisciplinary
NANOPARTICLES
NANOSCIENCE AND NANOTECHNOLOGY
Optical properties
PHOTOCATALYSIS
Quantum dots
Science
Science & Technology - Other Topics
Urea
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Summary:Photoluminescent graphene quantum dots (GQDs) have received enormous attention because of their unique chemical, electronic and optical properties. Here a series of GQDs were synthesized under hydrothermal processes in order to investigate the formation process and optical properties of N-doped GQDs. Citric acid (CA) was used as a carbon precursor and self-assembled into sheet structure in a basic condition and formed N-free GQD graphite framework through intermolecular dehydrolysis reaction. N-doped GQDs were prepared using a series of N-containing bases such as urea. Detailed structural and property studies demonstrated the formation mechanism of N-doped GQDs for tunable optical emissions. Hydrothermal conditions promote formation of amide between –NH 2 and –COOH with the presence of amine in the reaction. The intramoleculur dehydrolysis between neighbour amide and COOH groups led to formation of pyrrolic N in the graphene framework. Further, the pyrrolic N transformed to graphite N under hydrothermal conditions. N-doping results in a great improvement of PL quantum yield (QY) of GQDs. By optimized reaction conditions, the highest PL QY (94%) of N-doped GQDs was obtained using CA as a carbon source and ethylene diamine as a N source. The obtained N-doped GQDs exhibit an excitation-independent blue emission with single exponential lifetime decay.
ISSN:2045-2322
2045-2322
DOI:10.1038/srep05294