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

By Dan Qu, M. Zheng, Ligong Zhang, Haifeng Zhao, Zhigang Xie, X. Jing, R. Haddad, H. Fan, Zaicheng Sun. Scientific Reports, 2014

871 citations recorded by the source corpus.

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 –NH2 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.

Subfields: Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/811d41686e39eec929309572be02ef5195824470

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1. Bai Yang
2. Shoujun Zhu
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Citations in the corpus

• Carbon Quantum Dots: Surface Passivation and Functionalization (2016, background): “In a comprehensive work by Qu and co-workers later on, a systematic study of the formation mechanism and optimization for obtaining highly luminescent N-doped CQDs was performed [154].”
• The photoluminescence mechanism in carbon dots (graphene quantum dots, carbon nanodots, and polymer dots): current state and future perspective (2015, background): “The enhanced PL properties are attributed to the strongly PL centers on the surface, the synergy between the carbon core and the chemical groups, or solely to the presence of fluorophores [64].”
• Biomass-waste derived graphene quantum dots and their applications (2018, background): “amine, diethylene amine, ethylene diamine or urea as a source of nitrogen [105].”