Volume 12, Issue 19 p. 4432-4441
Full Paper

Manipulating the Optical Properties of Carbon Dots by Fine-Tuning their Structural Features

Hui Luo

Hui Luo

Department of Chemical Engineering, Imperial College London, London, SW7 2AZ UK

School of Engineering and Materials Science, Queen Mary University of London, London, E1 4NS UK

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Dr. Nikolaos Papaioannou

Dr. Nikolaos Papaioannou

School of Physics and Astronomy, Queen Mary University of London, London, E1 4NS UK

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Dr. Enrico Salvadori

Dr. Enrico Salvadori

School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS UK

Department of Chemistry, University of Turin, Turin, 10125 Italy

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Dr. Maxie M. Roessler

Dr. Maxie M. Roessler

School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS UK

Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, London, W12 0BZ UK

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Gereon Ploenes

Gereon Ploenes

Magnetic Resonance Research Center, Institute for Molecules and Materials, Radboud University, Nijmegen, 6525 AJ, Netherlands

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Dr. Ernst R. H. van Eck

Dr. Ernst R. H. van Eck

Magnetic Resonance Research Center, Institute for Molecules and Materials, Radboud University, Nijmegen, 6525 AJ, Netherlands

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Dr. Liviu C. Tanase

Dr. Liviu C. Tanase

National Institute of Materials Physics, Magurele-Ilfov, 077125 Romania

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Jingyu Feng

Jingyu Feng

Department of Chemical Engineering, Imperial College London, London, SW7 2AZ UK

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Dr. Yiwei Sun

Dr. Yiwei Sun

School of Physics and Astronomy, Queen Mary University of London, London, E1 4NS UK

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Yan Yang

Yan Yang

School of Engineering and Materials Science, Queen Mary University of London, London, E1 4NS UK

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Dr. Mohsen Danaie

Dr. Mohsen Danaie

Diamond Light Source Ltd., Electron Physical Science Imaging Centre, Harwell Science and Innovation Campus, Didcot, OX11 0DE UK

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Dr. Ana Belen Jorge

Dr. Ana Belen Jorge

School of Engineering and Materials Science, Queen Mary University of London, London, E1 4NS UK

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Dr. Andrei Sapelkin

Dr. Andrei Sapelkin

School of Physics and Astronomy, Queen Mary University of London, London, E1 4NS UK

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Prof. James Durrant

Prof. James Durrant

Department of Chemistry and Centre for Plastic Electronics, Imperial College London, London, SW7 2AZ UK

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Dr. Stoichko D. Dimitrov

Corresponding Author

Dr. Stoichko D. Dimitrov

SPECIFIC IKC, College of Engineering, Swansea University, Swansea, SA2 7AX UK

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Prof. Maria-Magdalena Titirici

Corresponding Author

Prof. Maria-Magdalena Titirici

Department of Chemical Engineering, Imperial College London, London, SW7 2AZ UK

School of Engineering and Materials Science, Queen Mary University of London, London, E1 4NS UK

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First published: 15 August 2019
Citations: 32

Graphical Abstract

Dot products: The structural evolution of hydrothermally synthesized carbon dots after oxidation and reduction is studied, and it is demonstrated how fine-tuning of the structure can dramatically change their optical properties. An in-depth spectroscopic analysis identifies the dynamics of photoluminescence, and this allows the relaxation pathways in these carbon dots to be fully resolved.

Abstract

As a new class of sustainable carbon material, “carbon dots” is an umbrella term covering many types of materials. Herein, a broad range of techniques was used to develop the understanding of hydrothermally synthesized carbon dots, and it is shown how fine-tuning the structural features by simple reduction/oxidation reactions can drastically affect their excited-state properties. Structural and spectroscopic studies found that photoluminescence originates from direct excitation of localized fluorophores involving oxygen functional groups, whereas excitation at graphene-like features leads to ultrafast phonon-assisted relaxation and largely quenches the fluorescent quantum yields. This is arguably the first study to identify the dynamics of photoluminescence including Stokes shift and allow the relaxation pathways in these carbon dots to be fully resolved. This comprehensive investigation sheds light on how understanding the excited-state relaxation processes in different carbon structures is crucial for tuning the optical properties for any potential commercial applications.

Conflict of interest

The authors declare no conflict of interest.