A planar- sheet nongraphitic zero- bandgap sp2 carbon phase made by the low- temperature reaction of γ- graphyne

AE Aliev and YZ Guo and AF Fonseca and JM Razal and Z Wang and DS Galvao and CM Bolding and NE Chapman-Wilson and VG Desyatkin and JE Leisen and LA Jr Ribeiro and GB Kanegae and P Lynch and JZ Zhang and MA Judicpa and AM Parra and MM Zhang and EL Gao and LF Hu and VO Rodionov and RH Baughman, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 122, e2413194122 (2025).

DOI: 10.1073/pnas.2413194122

The highest sheet symmetry form of graphyne, with one triple bond between each neighboring hexagon in graphene, irreversibly transforms exothermically at ambient pressure and low temperatures into a nongraphitic, planar- sheet, zero- bandgap phase consisting of intrasheet- bonded sp2 carbons. The synthesis of this sp2 carbon phase is demonstrated, and other carbon phases are described for possible future synthesis from graphyne without breaking graphyne bonds. While measurements and theory indicate that the reacting graphyne becomes nonplanar because of sheet wrinkling produced by dimensional mismatch between reacted and nonreacted sheet regions, sheet planarity is regained when the reaction is complete. Although the observed elimination of triple bonds to make parallel planar sp2 carbon sheets likely requires ordered transformation within each sheet, diffraction data for reacted multisheet stacks indicate that the relative lateral positions of neighboring sheets are disordered, as predicted, since no crystalline diffraction peak (other than for the intersheet spacing) is observed.

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