Functionalized graphdiyne nanowires: on-surface synthesis and assessment of band structure, flexibility, and information storage potential

With their extraordinary mechanical and electronic properties carbon-based nanomaterials are central in 21st century research and carry high hopes for future nanotechnology applications. Established sp2-hybridized scaffolds include carbon nanotubes (CNTs), graphene sheets, and graphene nanoribbons. Recently, the interest in carbon allotropes incorporating both sp2- and sp-hybridized atoms rose tremendously, especially for the most popular member, the so-called graphdiyne. According to theory, the related nanomaterials possess characteristics desirable for applications such as molecular electronics, energy storage, gas filtering and light harvesting. However, achieving the targeted materials with high quality remained challenging until now.
Here, we employed covalent on-surface synthesis on well-defined metal substrates under ultra-high vacuum (UHV) conditions to the homocoupling reaction of terminal alkyne compounds and fabricated the first functionalized graphdiyne (f-GDY) nanowires. Combining the substrate templating of the Ag(455) vicinal surface with specifically designed CN-functionalized precursors we achieved the controlled polymerization to atom-precise strands with their length reaching 40 nm. The left panel of Figure 1a depicts a scanning tunneling microscopy (STM) image of an area of the silver surface featuring two step edges where an example of such a f-GDY wire is lying at the lower side of the right step edge. The right panel displays a molecular model of the situation highlighting the structure of the nanowire adsorbed in the lower terrace (darker blue) consisting of covalently coupled monomers (red outline) with the CN moieties pointing towards the atoms of the upper terrace (brighter blue).
For assessing their electronic structure we conducted angle-resolved photoelectron spectroscopy (ARPES) at the APE beamline of Elettra. For a sample with adsorbed monomers and before thermal treatment the non-dispersing feature of the highest occupied molecular orbital (HOMO) can be identified in the ARPES data (Figure 1b, left) at a binding energy of 2.85 eV. After annealing the sample to 400 K (Figure 1b, right side), the HOMO level has evolved into a broad dispersing structure (white and blue) between ~2.5 and 3.5 eV. As explained in the article, the intrinsic band structure of this highest valence band of the f-GDY nanowires can be concluded from this data. It is depicted in Figure 1c and represents an approximately cosine-shaped band which is not crossed by other bands in accordance with theoretical predictions. The data indicates that the effective mass at the top of the band is smaller than 0.1 m0 and thus outrivals the competing 7-armchair graphene nanoribbons and polyphenylene nanowires.
Through tip manipulation experiments we demonstrated that the polymeric strands can be bent to an extraordinarily small bending radius below 2 nm without compromising the structural integrity. Furthermore, by utilizing attractive interactions between the CN functional group and the tip for small distances, the orientation of the individual benzonitrile subunits can be switched from trans to cis conformations. This enables the storage of information in the semiconducting polymer strand with a state-of-the-art density of about 0.3 bits/nm2. Figure 1e depicts the letter, “T”, “U”, and “M” encoded in conformational states of a tetrameric end of a f-GDY nanowire.
The work introduces f-GDY nanowires as novel carbon-based nanomaterial whereby the combination of sp- and sp2-hybridized bestows exciting electronic and mechanic characteristics desirable for a range of applications. 

Figure 1 Synthesis and characterization of functionalized graphdiyne nanowires. a) STM topograph of a f-GDY polymer covering the left step edge. b) ARPES data: Before annealing a non-dispersing feature originates from the HOMO of the monomer. After annealing a dispersing features (blue) can be identified. c) Schematic representation of the deduced intrinsic band structure of the f-GDY nanowires. d) STM topograph of a strongly bent nanowire. e) Information storage thru conformational cis-trans switching of benzonitrile units.


This research was conducted by the following research team:

Florian Klappenberger1, Raphael Hellwig1, Ping Du2, Tobias Paintner1, Martin Uphoff1, Liding Zhang1, Tao Lin1, Bahare Adebin Moghanaki1, Mateusz Paszkiewicz1, Ivana Vobornik3, Jun Fujii3, Olaf Fuhr2, Yi-Qi Zhang1, Francesco Allegretti1, Mario Ruben3,4 and Johannes V. Barth1 

Physik-Department, Technische Universität München, Garching, Germany
Institute für Nanotechnologie, Karlsruher Institut für Technologie, Eggenstein-Leopoldshafen, Germany
Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science Park, Trieste, Italy
IPCMS-CNRS, Universitè de Strasbourg, Strasbourg, France 

Contact persons:

Florian Klappenberger, email:


F. Klappenberger, R. Hellwig, P. Du, T. Paintner, M. Uphoff, L. Zhang, T. Lin, B. Abedin Moghanaki, M. Paszkiewicz, I. Vobornik, J. Fujii, O. Fuhr, Y. Q. Zhang, F. Allegretti, M. Ruben, and J. V. Barth, “Functionalized graphdiyne nanowires: On-surface synthesis and assessment of band structure, flexibility, and information storage potential”, Small (2017)

Last Updated on Monday, 26 February 2018 14:54