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Atomically-Precise Assembly of Graphene Nanoribbons

What is the scientific achievement?

CFN users from the University of Nebraska designed and synthesized a new type of graphene nanoribbon, decorated with phenyl functional groups that shift the ribbon energy band energies. Further, the phenyl functionalization drive ribbon self-assembly into larger, ordered graphene patterns containing atomically-precise nanopores, which were imaged by non-contact atomic force microscopy.

Why does this achievement matter?

Graphene has superior electronic properties, and the energy-band tunability of these functionalized ribbons holds promise for their use as building blocks of electronic devices.  Graphene containing atomically-precise nanopores has strong potential for membrane applications.

What are the details?

Graphene nanoribbons are heavily investigated nanomaterials due to their tunable physical properties and potential as nanoscale building blocks for electronic devices.  Nanoribbons can be synthesized with atomic precision by on-surface approaches from specially designed molecular precursors.  While a considerable number of ribbons with very diverse structures and properties have been demonstrated in recent years, there have been only limited examples of on-surface synthesized GNRs modified with functional groups.  In this work, we designed a nanoribbon in which the chevron-shaped backbone is decorated with phenyl functionalities, and demonstrate the on-surface synthesis of these graphene nanoribbon on gold (111) surfaces.  This phenyl modification influences the assembly of the nanoribbon polymer precursors through π–π interactions.  Scanning tunneling spectroscopy of the modified nanoribbons on Au(111) revealed a band gap of 2.50 ± 0.02 eV, which is comparable to that of the parent chevron graphene nanoribbon. The phenyl functionalization leads to a shift of the band edges to lower energies, suggesting that this is a useful tool for band structure engineering. Phenyl-modified graphene nanoribbons also self-assemble into larger, ordered graphene structures,  and we show how this process can be used to engineer atomically precise graphene nanopores. A similar functionalization approach could be potentially applied to other graphene nanoribbons, to affect their on-surface assembly, modify their electronic properties, and realize graphene nanopores with different geometries.

CFN Capabilities:

The CFN Proximal Probes facility was used to carry out low-temperature, non-contact atomic force microscopy of assembled graphene nanoribbons.

Publication Reference

Mikhail Shekhirev, Percy Zahl, and Alexander Sinitskii, Phenyl Functionalization of Atomically Precise Graphene Nanoribbons for Engineering Inter-ribbon Interactions and Graphene Nanopores, ACS Nano 12, 8662 (2018).

DOI: 10.1021/acsnano.8b04489
https://pubs.acs.org/doi/10.1021/acsnano.8b04489

Acknowledgement of Support

The work was supported by the Office of Naval Research (N00014-16-1-2899) and the National Science Foundation (CHE-1455330). This research used resources of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704

2018-13118  |  INT/EXT  |  Media & Communications Office