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The electron–hole exchange interaction significantly influences the optical properties of excitons and radiative decay. However, exciton dynamics in luminescent carbon dots (Cdots) is still not clear. In this study, we have developed a simple and efficient one-step strategy to synthesize luminescent Cdots using the pyrolysis of oleylamine. The sp2 clusters of a few aromatic rings are responsible for the observed blue photoluminescence. The size of these clusters can be tuned by controlling the reaction time, and the energy gap between the ππ * states of the sp2 domains decreases as the sp2 cluster size increases. More importantly, the strong electron–hole exchange interaction results in the splitting of the exciton states of the sp2 clusters into the singlet-bright and triplet-dark states with an energy difference ΔE , which decreases with increasing sp2 cluster size owing to the reduction of the confinement energy and the suppression of the electron–hole exchange interaction.

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Publication history

Received: 22 July 2015
Revised: 29 October 2015
Accepted: 30 October 2015
Published: 11 December 2015
Issue date: February 2016

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© Tsinghua University Press and Springer-Verlag Berlin Heidelberg 2015

Acknowledgements

Acknowledgements

Q. H. X. gratefully thanks the strong support from Singapore National Research Foundation through a Competitive Research Program (No. NRF-CRP-6-2010-2), and Singapore Ministry of Education via two Tier2 grants (Nos. MOE2011-T2-2-051 and MOE2011-T2-2-085) and a Tier1 grant (No. 2013-T1-002-232).

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Email: nanores@tup.tsinghua.edu.cn

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