Controllable conversion of quasi-freestanding polymer chains to graphene nanoribbons

In the bottom-up synthesis of graphene nanoribbons (GNRs) from self-assembled linear polymer intermediates, surface-assisted cyclodehydrogenations usually take place on catalytic metal surfaces. Here we demonstrate the formation of GNRs from quasi-freestanding polymers assisted by hole injections fr...

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Bibliographic Details
Published in:Nature communications 2017-03, Vol.8 (1), p.14815-14815, Article 14815
Main Authors: Ma, Chuanxu, Xiao, Zhongcan, Zhang, Honghai, Liang, Liangbo, Huang, Jingsong, Lu, Wenchang, Sumpter, Bobby G., Hong, Kunlun, Bernholc, J., Li, An-Ping
Format: Article
Language:English
Subjects:
119/118
639/301/357/341
639/638/403/934
639/638/77/885
639/925/918/1055
Electrons
Graphene
Humanities and Social Sciences
MATERIALS SCIENCE
multidisciplinary
Polymerization
Polymers
Science
Science (multidisciplinary)
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Summary:In the bottom-up synthesis of graphene nanoribbons (GNRs) from self-assembled linear polymer intermediates, surface-assisted cyclodehydrogenations usually take place on catalytic metal surfaces. Here we demonstrate the formation of GNRs from quasi-freestanding polymers assisted by hole injections from a scanning tunnelling microscope (STM) tip. While catalytic cyclodehydrogenations typically occur in a domino-like conversion process during the thermal annealing, the hole-injection-assisted reactions happen at selective molecular sites controlled by the STM tip. The charge injections lower the cyclodehydrogenation barrier in the catalyst-free formation of graphitic lattices, and the orbital symmetry conservation rules favour hole rather than electron injections for the GNR formation. The created polymer–GNR intraribbon heterostructures have a type-I energy level alignment and strongly localized interfacial states. This finding points to a new route towards controllable synthesis of freestanding graphitic layers, facilitating the design of on-surface reactions for GNR-based structures. A key step in the on-surface synthesis of graphene nanoribbons is thermal annealing of polymer precursors on a metal substrate. Here, Ma et al . decouple the cyclodehydrogenation reaction from the catalytic metal substrate and grow graphene nanoribbons by injecting charges at molecular sites.
ISSN:2041-1723
2041-1723
DOI:10.1038/ncomms14815