Carbon nanostructures with zigzag edges exhibit unique properties—such as localized electronic states and spins—with exciting potential applications. Such nanostructures however are generally synthesized under vacuum because their zigzag edges are unstable under ambient conditions: a barrier that must be surmounted to achieve their scalable integration into devices for practical purposes. Here we show two chemical protection/deprotection strategies, demonstrated on labile, air-sensitive chiral graphene nanoribbons. Upon hydrogenation, the chiral graphene nanoribbons survive exposure to air, after which they are easily converted back to their original structure by annealing. We also approach the problem from another angle by synthesizing a form of the chiral graphene nanoribbons that is functionalized with ketone side groups. This oxidized form is chemically stable and can be converted to the pristine hydrocarbon form by hydrogenation and annealing. In both cases, the deprotected chiral graphene nanoribbons regain electronic properties similar to those of the pristine nanoribbons. We believe both approaches may be extended to other graphene nanoribbons and carbon-based nanostructures.
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All relevant data generated and analysed during this study, including STM and scanning tunnelling spectroscopy data and theoretical calculations, are included in this Article and its Supplementary Information and are also available from the authors upon reasonable request. Source data are provided with this paper.
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Research was supported by MCIN/AEI/10.13039/501100011033 (grant nos PID2019-107338RB-C62 (D.P.), PID2019-107338RB-C63 (M.C. and D.G.d.O.) and FJC2019-041202-I (F.S.)); the European Union’s Horizon 2020 programme (grant nos 863098 (D.P.) and 635919 (D.G.d.O.), and Marie Skłodowska-Curie Actions Individual Fellowship no. 101022150 (T.W.)); the Gobierno Vasco (grant no. PIBA_2020_1_0036 (D.G.d.O.)); the Xunta de Galicia (Centro Singular de Investigación de Galicia, 2019–2022, grant no. ED431G2019/03 (D.P.)); the European Regional Development Fund; the Praemium Academie of the Academy of Science of the Czech Republic (GACR project no. 20-13692X (P.J.)); the Czech Nanolab Research Infrastructure supported by MEYS CR (project no. LM2018110 (P.J.)); and the Operational Programme for Research, Development and Education of the European Regional Development Fund (project no. CZ.02.1.01/0.0/0.0/16_019/0000754 (P.J.)). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.
The authors have no competing interests.
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Extended Data Fig. 1 XPS analysis monitoring the hydrogenation/dehydrogenation process of pristine and ketone-functionalized ribbons.
(a) C1s XPS spectra (symbols) of p-chGNRs “as grown” (top), after hydrogenation (middle) and after subsequent annealing (bottom), along with the fit (solid curve) and its associated components (coloured peaks). The data reveal the successful hydrogenation and its reversibility. (b) C1s XPS spectra (symbols) of k-chGNRs “as grown” (top), after hydrogenation (middle) and after subsequent annealing (bottom), along with the fit (solid curve) and its associated components (coloured peaks). The data reveal the gradual deoxidation upon hydrogenation and the subsequent annealing. Dashed lines act as a guide to the eye to compare the maxima on each of the spectra. Details about the fitting procedure are given in the methods section.
Comparison between the structures of the two types of ketone-functionalized GNRs that were observed. (a) Typical STM image of a self-assembled island that contains both types of ketone-GNR. I = 50 pA, Vbias = −0.5 V. (b) BR-STM image of a metal-coordinated and (c) typical section of a ketone-NR island. Both constant height, CO tip, Vbias = 4 mV and 5 mV, respectively. Scale bars are both 500 pm. (d) and (e) Models of the metal-coordinated and typical islands, with suggested positions for gold adatoms in the metal-coordinated model.
(a) Overview STM image of a ketone-GNR sample that was exposed to air for 24 minutes, without any further treatment. I = 50 pA; Vbias = 1.5 V. (b) and (c): STM images of the same sample after annealing to 200 °C for 1 hour. (b) I = 20 pA; Vbias = −0.8 V. (c) I = 30 pA; Vbias = −0.8 V. Although most have desorbed, a notable number of contaminants are still present on the surface after the annealing treatment. Islands of alkyl chain contamination from the ambient conditions are indicated in (c) with a blue arrow.
Scanning probe microscopy images for Fig. 2.
Scanning probe microscopy images for Fig. 3.
Conductance spectra, scanning probe microscopy images, calculated band structure and calculated wavefunctions for Fig. 4.
Conductance spectra and calculated atomic positions for Fig. 5
Scanning probe microscopy images for Fig. 6.
Unprocessed XPS data for the pristine and ketone-functionalized ribbons as grown, after hydrogen exposure and after subsequent annealing.
Scanning probe microscopy images for Extended Data Fig. 2.
Scanning probe microscopy images for Extended Data Fig. 3.
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Lawrence, J., Berdonces-Layunta, A., Edalatmanesh, S. et al. Circumventing the stability problems of graphene nanoribbon zigzag edges. Nat. Chem. 14, 1451–1458 (2022). https://doi.org/10.1038/s41557-022-01042-8