On-Surface
Synthesis of Unsaturated Carbon Nanostructures
with Regularly Fused Pentagon–Heptagon Pairs

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Abstract

Multiple fused pentagon–heptagon pairs are frequently found as defects at the grain boundaries of the hexagonal graphene lattice and are suggested to have a fundamental influence on graphene-related materials. However, the construction of sp ²-carbon skeletons with multiple regularly fused pentagon–heptagon pairs is challenging. In this work, we found that the pentagon–heptagon skeleton of azulene was rearranged during the thermal reaction of an azulene-incorporated organometallic polymer on Au(111). The resulting sp ²-carbon frameworks were characterized by high-resolution scanning probe microscopy techniques and feature novel polycyclic architectures composed of multiple regularly fused pentagon–heptagon pairs. Moreover, the calculated analysis of its aromaticity revealed a peculiar polar electronic structure.

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Most cited references 51

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Nucleus-independent chemical shifts (NICS) as an aromaticity criterion.

Zhongfang Chen, Chaitanya S Wannere, Clémence Corminboeuf … (2005)

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Grains and grain boundaries in single-layer graphene atomic patchwork quilts.

Pinshane Y Huang, Carlos S Ruiz-Vargas, Arend M van der Zande … (2011)

The properties of polycrystalline materials are often dominated by the size of their grains and by the atomic structure of their grain boundaries. These effects should be especially pronounced in two-dimensional materials, where even a line defect can divide and disrupt a crystal. These issues take on practical significance in graphene, which is a hexagonal, two-dimensional crystal of carbon atoms. Single-atom-thick graphene sheets can now be produced by chemical vapour deposition on scales of up to metres, making their polycrystallinity almost unavoidable. Theoretically, graphene grain boundaries are predicted to have distinct electronic, magnetic, chemical and mechanical properties that strongly depend on their atomic arrangement. Yet because of the five-order-of-magnitude size difference between grains and the atoms at grain boundaries, few experiments have fully explored the graphene grain structure. Here we use a combination of old and new transmission electron microscopy techniques to bridge these length scales. Using atomic-resolution imaging, we determine the location and identity of every atom at a grain boundary and find that different grains stitch together predominantly through pentagon-heptagon pairs. Rather than individually imaging the several billion atoms in each grain, we use diffraction-filtered imaging to rapidly map the location, orientation and shape of several hundred grains and boundaries, where only a handful have been previously reported. The resulting images reveal an unexpectedly small and intricate patchwork of grains connected by tilt boundaries. By correlating grain imaging with scanning probe and transport measurements, we show that these grain boundaries severely weaken the mechanical strength of graphene membranes but do not as drastically alter their electrical properties. These techniques open a new window for studies on the structure, properties and control of grains and grain boundaries in graphene and other two-dimensional materials.

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On-surface synthesis of graphene nanoribbons with zigzag edge topology

Pascal Ruffieux, Shiyong Wang, Bo Yang … (2016)

Graphene-based nanostructures exhibit electronic properties that are not present in extended graphene. For example, quantum confinement in carbon nanotubes and armchair graphene nanoribbons leads to the opening of substantial electronic bandgaps that are directly linked to their structural boundary conditions. Nanostructures with zigzag edges are expected to host spin-polarized electronic edge states and can thus serve as key elements for graphene-based spintronics. The edge states of zigzag graphene nanoribbons (ZGNRs) are predicted to couple ferromagnetically along the edge and antiferromagnetically between the edges, but direct observation of spin-polarized edge states for zigzag edge topologies--including ZGNRs--has not yet been achieved owing to the limited precision of current top-down approaches. Here we describe the bottom-up synthesis of ZGNRs through surface-assisted polymerization and cyclodehydrogenation of specifically designed precursor monomers to yield atomically precise zigzag edges. Using scanning tunnelling spectroscopy we show the existence of edge-localized states with large energy splittings. We expect that the availability of ZGNRs will enable the characterization of their predicted spin-related properties, such as spin confinement and filtering, and will ultimately add the spin degree of freedom to graphene-based circuitry.

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Author and article information

Journal

Journal ID (nlm-ta): J Am Chem Soc

Journal ID (iso-abbrev): J. Am. Chem. Soc

Journal ID (publisher-id): ja

Journal ID (coden): jacsat

Title: Journal of the American Chemical Society

Publisher: American Chemical Society

ISSN (Print): 0002-7863

ISSN (Electronic): 1520-5126

Publication date (Electronic): 19 May 2020

Publication date (Print): 10 June 2020

Volume: 142

Issue: 23

Pages: 10291-10296

Affiliations

[† ]Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany

[‡ ]Department Chemie, Johannes Gutenberg-University Mainz , Duesbergweg 10-14, 55128 Mainz, Germany

[§ ]Empa, Swiss Federal Laboratories for Materials Science and Technology , 8600 Dübendorf, Switzerland

[∥ ]Organic and Carbon Nanomaterials Unit, Okinawa Institute of Science and Technology Graduate University , 1919-1 Tancha, Onna-son, Kunigami, Okinawa 904-0495, Japan

[⊥ ]Department of Chemistry and Biochemistry, University of Bern , 3012 Bern, Switzerland

Author notes

[* ]E-mail: narita@ 123456mpip-mainz.mpg.de .

[* ]E-mail: roman.fasel@ 123456empa.ch .

[* ]E-mail: muellen@ 123456mpip-mainz.mpg.de .

Article

DOI: 10.1021/jacs.0c03635

PMC ID: 7304065

PubMed ID: 32428409

SO-VID: f21057c4-c7fd-4365-a154-6a7a05ceab21

License:

This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited.

History

Date received : 02 April 2020

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ScienceOpen disciplines: Chemistry

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