Topological Influence of Sextets on Graphene Oxide Nanostructure

Abstract

Graphene Oxide (GO) remains a perennial chemical enigma despite its utility in preparing graphene and its functionalization. Epoxides and tertiary alcohols are construed as primary functional groups, but the structural motifs, spectra, and physicochemical properties remain largely inexplicable. Our graph theoretic perturbational analysis of introducing defects (sp3 carbons) on graphene shows the induction of sextets that topologically force 1, 4-quinoidal channels. Edge defects minimize these, whose propagation is halted by vertex anti-defects. Molecular models show that epoxidation creates a diradical centered on two cove-end carbons due to close-lying frontier orbitals. This drives the cascade addition of hydroxides, yielding the 1:2 ratio of epoxides and hydroxides. This nanostructure accounts for the cation exchange, acidity, anionic nature of GO, and topological conditions that break its sigma framework. The simulated spectra of a 2D sheet with this nanostructure correlate pleasantly with experiments, emphasizing the dominant role of sextet topology on the surface chemistry of graphene.