More than five hundred crystalline forms of carbon have been theoretically predicted to date, but few have been synthesized. In most of the existing crystalline carbons, each atom has either 4 immediate neighbors (chemists sometimes refer to this as sp3 hybridization), or 3 neighbors (sp2 hybridization). The all-sp3 carbon is diamond. A large variety of all-sp2 carbons are known, including graphite, graphene, fullerenes, and nanotubes. A carbon atom can also participate in an arrangement where it has only two immediate neighbors (sp1 hybridization). However, pure carbon crystals featuring sp1 hybridization are exceedingly rare.
One such material is γ-graphyne, a form of carbon combining sp2 and sp1 atoms. It can be formally viewed as graphene uniformly expanded by two-carbon acetylenic units. To date, synthesis of bulk γ graphyne has remained a challenge.
In this study, macromolecular searchers developed a scalable method for the synthesis of multilayer γ-graphyne through a 2D cross-coupling polymerization. Investigations of the physical properties of this new material were assisted by our collaborators from UT Dallas, Stanford, Stanford Synchrotron Radiation Lightsource, University of Campinas in Brazil, and Oxford Instruments Asylum Research. The reported methodology is scalable and inspires extension to other rigid carbon networks, including allotropes of the graphyne family.
ɣ-Graphyne is a stable semiconductor with a moderate (0.5 eV) band gap, ultrafast charge carrier mobility, high heat conductance, and exceptional strength.
Because of these properties ɣ-graphyne has the potential to form the basis for the next generation of carbon-based electronics, photonics, and solar cells. Graphyne-based devices can be ultra-thin, flexible, and operate at speeds unattainable by silicon chips.