Emissive brightening in molecular graphene nanoribbons by twilight states

Carbon nanomaterials are expected to be bright and efficient emitters, but structural disorder, intermolecular interactions and the intrinsic presence of dark states suppress their photoluminescence. Here, we study synthetically-made graphene nanoribbons with atomically precise edges and which are d...

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Bibliographic Details
Published in:Nature communications 2024-04, Vol.15 (1), p.2985-2985, Article 2985
Main Authors: Sturdza, Bernd K., Kong, Fanmiao, Yao, Xuelin, Niu, Wenhui, Ma, Ji, Feng, Xinliang, Riede, Moritz K., Bogani, Lapo, Nicholas, Robin J.
Format: Article
Language:English
Subjects:
639/301/119/995
639/638/440/949
639/766/119/1000/1016
Brightening
Emission
Emissions
Emitters
Graphene
Humanities and Social Sciences
Luminescence
multidisciplinary
Nanomaterials
Nanoribbons
Nanotechnology
Photoluminescence
Photons
Science
Science (multidisciplinary)
Spectral resolution
Thin films
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Summary:Carbon nanomaterials are expected to be bright and efficient emitters, but structural disorder, intermolecular interactions and the intrinsic presence of dark states suppress their photoluminescence. Here, we study synthetically-made graphene nanoribbons with atomically precise edges and which are designed to suppress intermolecular interactions to demonstrate strong photoluminescence in both solutions and thin films. The resulting high spectral resolution reveals strong vibron-electron coupling from the radial-breathing-like mode of the ribbons. In addition, their cove-edge structure produces inter-valley mixing, which brightens conventionally-dark states to generate hitherto-unrecognised twilight states as predicted by theory. The coupling of these states to the nanoribbon phonon modes affects absorption and emission differently, suggesting a complex interaction with both Herzberg–Teller and Franck– Condon coupling present. Detailed understanding of the fundamental electronic processes governing the optical response will help the tailored chemical design of nanocarbon optical devices, via gap tuning and side-chain functionalisation. The authors demonstrate that the band structure of graphene nanoribbons is modulated by cove edges, brightening the luminescence 4-fold via emission from otherwise dark twilight states. High spectral resolution of the optical response reveals strong vibron-electron coupling
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-024-47139-1