University of Oulu

Boukhvalov, D.W., Osipov, V.Y., Hogan, B.T. et al. A comprehensive model of nitrogen-free ordered carbon quantum dots. Discover Nano 18, 1 (2023).

A comprehensive model of nitrogen-free ordered carbon quantum dots

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Author: Boukhvalov, Danil W.1,2; Osipov, Vladimir Yu.3; Hogan, Benjamin Thomas4,5,6;
Organizations: 1College of Science, Institute of Materials Physics and Chemistry, Nanjing Forestry University, Nanjing, 210037, People’s Republic of China
2Institute of Physics and Technology, Ural Federal University, Mira 19 Str., Yekaterinburg, Russia, 620002
3Ioffe Institute, Polytechnicheskaya 26, Saint Petersburg, Russia, 194021
4STEMM Laboratory, University of Exeter, North Park Road, Exeter, EX4 4QF, UK
5Department of Electrical and Information Engineering, University of Oulu, 90014, Oulu, Finland
6Department of Chemical Engineering, Queen’s University, 45 Union St., Kingston, ON, K7L 3N6, Canada
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 3.7 MB)
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Language: English
Published: Springer Nature, 2023
Publish Date: 2023-08-16


We propose and demonstrate a novel range of models to accurately determine the optical properties of nitrogen-free carbon quantum dots (CQDs) with ordered graphene layered structures. We confirm the results of our models against the full range of experimental results for CQDs available from an extensive review of the literature. The models can be equally applied to CQDs with varied sizes and with different oxygen contents in the basal planes of the constituent graphenic sheets. We demonstrate that the experimentally observed blue fluorescent emission of nitrogen-free CQDs can be associated with either small oxidised areas on the periphery of the graphenic sheets, or with sub-nanometre non-functionalised islands of sp²-hybridised carbon with high symmetry confined in the centres of oxidised graphene sheets. Larger and/or less symmetric non-functionalised regions in the centre of functionalised graphene sheet are found to be sources of green and even red fluorescent emission from nitrogen-free CQDs. We also demonstrate an approach to simplify the modelling of the discussed sp²-islands by substitution with equivalent strained polycyclic aromatic hydrocarbons. Additionally, we show that the bandgaps (and photoluminescence) of CQDs are not dependent on either out-of-plane corrugation of the graphene sheet or the spacing between sp²-islands. Advantageously, our proposed models show that there is no need to involve light-emitting polycyclic aromatic molecules (nanographenes) with arbitrary structures grafted to the particle periphery to explain the plethora of optical phenomena observed for CQDs across the full range of experimental works.

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Series: Nanoscale research letters
ISSN: 1931-7573
ISSN-E: 1556-276X
ISSN-L: 1931-7573
Volume: 18
Issue: 1
Pages: 1 - 15
DOI: 10.1186/s11671-023-03773-0
Type of Publication: A1 Journal article – refereed
Field of Science: 114 Physical sciences
Funding: D.W.B. acknowledges support from the Russian Science Foundation (Project No. 21-12-00392). V.Y.O. acknowledges the support from Ioffe Institute (Project No. 0040-2019-0013). AB and BTH acknowledge financial support from the Engineering and Physical Sciences Research Council (EPSRC) of the United Kingdom via the EPSRC Centre for Doctoral Training in Electromagnetic Metamaterials (Grant No. EP/L015331/1) and via Grant No. EP/N035569/1.
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