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Graphyne

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Not to be confused with Graphene, Grapheme, or Graphane.
Graphyne

Chemical structure of graphyne-1
Identifiers
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Graphyne-n varieties, where n indicates the number of carbon–carbon triple bonds in a link between two adjacent hexagons. Graphyne is graphyne-1; graphdiyne is graphyne-2.

Graphyne is an allotrope of carbon. Although it has been studied in theoretical models, it is very difficult to synthesize and only small amounts of uncertain purity have been created. Its structure is one-atom-thick planar sheets of sp and sp2-bonded carbon atoms arranged in crystal lattice. It can be seen as a lattice of benzene rings connected by acetylene bonds. The material is called graphyne-n when benzene rings are connected by n sequential acetylene molecules, and graphdiyne for a particular case of n = 2 (diacetylene links).

Depending on the content of acetylene groups, graphyne can be considered a mixed hybridization, spk, where k can be 1 or 2,[1][2] and thus differs from the hybridization of graphene (considered pure sp2) and diamond (pure sp3).

First-principles calculations showed that periodic graphyne structures and their boron nitride analogues are stable. The calculations used phonon dispersion curves and ab-initio finite temperature, quantum mechanical molecular dynamics simulations.[3]

History

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Graphyne was first theoretically proposed by Baughman et al. in 1987.[4] In 2010, Li et al. developed the first successful methodology for creating graphdiyne films using the Glaser–Hay cross-coupling reaction with hexaethynylbenzene.[5] The proposed approach makes it possible to synthesize nanometer-scale graphdiyne and graphtetrayne, which lack long-range order. In 2019, Cui and co-workers reported on a mechanochemical technique for obtaining graphyne using benzene and calcium carbide.[6] Although a gram-scale graphyne can be obtained using this approach, graphynes with long-range crystallinity over a large area remain elusive.

In 2022, synthesis of multi-layered γ‑graphyne was successfully performed through the polymerization of 1,3,5-tribromo-2,4,6-triethynylbenzene under Sonogashira coupling conditions. Near-infrared spectroscopy and cyclic voltammetry of the material determined the bandgap as 0.48 ± 0.05 eV, which agrees with the theoretical prediction for graphyne-based materials.[7]: 4 [8]

Synthesis

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Despite numerous efforts by different approaches, no synthesis method has been discovered to create quality graphyne. The small impure amounts created to date do not allow characterization sufficient to verify theoretical properties.[7]: 12 

Structure

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Through the use of computer models scientists have predicted several properties of the substance on assumed geometries of the lattice. Its proposed structures are derived from inserting acetylene bonds in place of carbon-carbon single bonds in a graphene lattice.[9] Graphyne is theorized to exist in multiple geometries. This variety is due to the multiple arrangements of sp and sp2 hybridized carbon. The proposed geometries include a hexagonal lattice structure and a rectangular lattice structure.[10] Out of the theorized structures the rectangular lattice of 6,6,12-graphyne may hold the most potential for future applications.

Properties

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Models predict that graphyne has the potential for Dirac cones on its double and triple bonded carbon atoms.[citation needed] Due to the Dirac cones, the conduction and valence bands meet in a linear fashion at a single point in the Fermi level. The advantage of this scheme is that electrons behave as if they have no mass, resulting in energies that are proportional to the momentum of the electrons. Like in graphene, hexagonal graphyne has electric properties that are direction independent. However, due to the symmetry of the proposed rectangular 6,6,12-graphyne the electric properties would change along different directions in the plane of the material.[10] This unique feature of its symmetry allows graphyne to self-dope meaning that it has two different Dirac cones lying slightly above and below the Fermi level.[10] The self-doping effect of 6,6,12-graphyne can be effectively tuned by applying in-plane external strain.[11] Graphyne samples synthesized to date have shown a melting point of 250-300 °C, low reactivity in decomposition reactions with oxygen, heat and light.[9]

Potential applications

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It has been hypothesized that graphyne is preferable to graphene for specific applications owing to its particular energy structure, namely direction-dependent Dirac cones.[12][13] The directional dependency of 6,6,12-graphyne could allow for electrical grating on the nanoscale.[14] This could lead to the development of faster transistors and nanoscale electronic devices.[10][15][16] Recently it was demonstrated that photoinduced electron transfer from electron-donating partners to γ-graphyne is favorable and occurs on nano to sub-picosecond time scale.[17]

References

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  1. ^ Heimann, R.B.; Evsvukov, S.E.; Koga, Y. (1997). "Carbon allotropes: a suggested classification scheme based on valence orbital hybridization". Carbon. 35 (10–11): 1654–1658. doi:10.1016/S0008-6223(97)82794-7.
  2. ^ Enyashin, Andrey N.; Ivanovskii, Alexander L. (2011). "Graphene Allotropes". Physica Status Solidi B. 248 (8): 1879–1883. Bibcode:2011PSSBR.248.1879E. doi:10.1002/pssb.201046583. S2CID 125591804.
  3. ^ Özçelik, V. Ongun; Ciraci, S. (January 10, 2013). "Size Dependence in the Stabilities and Electronic Properties of α-Graphyne and Its Boron Nitride Analogue". The Journal of Physical Chemistry C. 117 (5): 2175–2182. arXiv:1301.2593. doi:10.1021/jp3111869. S2CID 44136901.
  4. ^ Baughman, R. H.; Eckhardt, H.; Kertesz, M. (1987). "Structure‐property predictions for new planar forms of carbon: Layered phases containing sp2 and sp atoms". The Journal of Chemical Physics. 87 (11): 6687–6699. Bibcode:1987JChPh..87.6687B. doi:10.1063/1.453405.
  5. ^ Li, G.; Li, Y.; Lui, H.; Guo, Y.; Li, Y.; Zhu, D. (2010). "Architecture of graphdiyne nanoscale films". Chemical Communications. 46 (19): 3256–3258. doi:10.1039/B922733D. PMID 20442882.
  6. ^ Li, Q.; Yang, C.; Wu, L.; Wang, H.; Cui, X. (2019). "Converting benzene into γ-graphyne and its enhanced electrochemical oxygen evolution performance". Journal of Materials Chemistry A. 7 (11): 5981–5990. doi:10.1039/C8TA10317H. S2CID 104431102.
  7. ^ a b Li, Jiaqiang; Han, Yu (2023-03-01). "Artificial carbon allotrope γ-graphyne: Synthesis, properties, and applications". Giant. 13: 100140. doi:10.1016/j.giant.2023.100140. ISSN 2666-5425.
  8. ^ Desyatkin, V. G.; Martin, W. B.; Aliev, A. E.; Chapman, N. E.; Fonseca, A. F.; Galvão, D. S.; Miller, E. R.; Stone, K. H.; Wang, Z.; Zakhidov, D.; Limpoco, F. T.; Almahdali, S. R.; Parker, S. M.; Baughman, R. H.; Rodionov, V. O. (2022). "Scalable Synthesis and Characterization of Multilayer γ‑Graphyne, New Carbon Crystals with a Small Direct Band Gap". Journal of the American Chemical Society. 144 (39): 17999–18008. arXiv:2301.05291. doi:10.1021/jacs.2c06583. PMID 36130080. S2CID 252438218.
  9. ^ a b Kim, Bog G.; Choi, Hyoung Joon (2012). "Graphyne: Hexagonal network of carbon with versatile Dirac cones". Physical Review B. 86 (11): 115435. arXiv:1112.2932. Bibcode:2012PhRvB..86k5435K. doi:10.1103/PhysRevB.86.115435. S2CID 119288235.
  10. ^ a b c d Dumé, Belle (1 March 2012). "Could graphynes be better than graphene?". Physics World. Institute of Physics.
  11. ^ Wang, Gaoxue; Si, Mingsu; Kumar, Ashok; Pandey, Ravindra (May 26, 2014). "Strain engineering of Dirac cones in graphyne". Applied Physics Letters. 104 (21): 213107. Bibcode:2014ApPhL.104u3107W. doi:10.1063/1.4880635.
  12. ^ Malko, Daniel; Neiss, Christian; Viñes, Francesc; Görling, Andreas (24 February 2012). "Competition for Graphene: Graphynes with Direction-Dependent Dirac Cones" (PDF). Phys. Rev. Lett. 108 (8): 086804. Bibcode:2012PhRvL.108h6804M. doi:10.1103/PhysRevLett.108.086804. hdl:2445/65316. PMID 22463556.
  13. ^ Schirber, Michael (24 February 2012). "Focus: Graphyne May Be Better than Graphene". Physics. 5 (24): 24. Bibcode:2012PhyOJ...5...24S. doi:10.1103/Physics.5.24.
  14. ^ Bardhan, Debjyoti (2 March 2012). "Novel new material graphyne can be a serious competitor to graphene". techie-buzz.com.
  15. ^ Cartwright, J. (1 March 2012). "Graphyne could be better than graphene". news.sciencemag.org. Archived from the original on 2 October 2012.
  16. ^ "Graphyne Better Than Graphene?". Materials Today. 5 March 2012.
  17. ^ Stasyuk, O.A.; Stasyuk, A.J.; Solà, M.; Voityuk, A.A. (2022). "γ-graphyne: a promising electron acceptor for organic photovoltaics". Materials & Design. 225: 111526. doi:10.1016/j.matdes.2022.111526. hdl:10256/22532. S2CID 254961210.
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