Oxygen-Driven Unzipping of Graphitic Materials

Abstract

Optical microscope images of graphite oxide (GO) reveal the occurrence of fault lines resulting from the oxidative processes. The fault lines and cracks of GO are also responsible for their much smaller size compared with the starting graphite materials. We propose an unzipping mechanism to explain the formation of cracks on GO and cutting of carbon nanotubes in an oxidizing acid. GO unzipping is initiated by the strain generated by the cooperative alignment of epoxy groups on a carbon lattice. We employ two small GO platelets to show that through the binding of a new epoxy group or the hopping of a nearby existing epoxy group, the unzipping process can be continued during the oxidative process of graphite. The same epoxy group binding pattern is also likely to be present in an oxidized carbon nanotube and cause its breakup.

Functionalized Single Graphene Sheets Derived from Splitting Graphite Oxide

“…According to a recently proposed mechanism, when several epoxy groups line up, the sheet can form a kink that partially releases this strain energy and makes this configuration energetically favored. 25 Therefore, during the oxidation of graphite, epoxy groups tend to form chains across the graphite surface through this cooperative reaction (Figure 3a and a′). Because of the elimination of oxygen from functional groups and any residual water during the rapid heating, elemental analysis shows an increase in the C/O ratio from 2:1 in graphite oxide to 10:1 in the reduced state (SI4, Supporting Information).…”

Transforming moiré blisters into geometric graphene nano-bubbles

“…At a second stage of oxidative heating, the graphene edges are nicked by a catalytic reaction involving the oxidized Ru(0001) surface to produce CO/CO 2 in the presence of oxygen 27 . Once a hole is formed, oxidative etching of graphene through the edges of the hole is facile owing to the high reactivity of the unsaturated carbon atoms at the edges.…”

Intercalation and Stitching of Graphite Oxide with Diaminoalkanes

“…6,[31][32][33] Interchain interactions and packing arrangements can be inferred from the intensity and shape of the bending vibration, observed between 1466 and 1472 cm -1 . Higher frequencies are indicative of all-trans chains in a crystalline state.…”

“…The latter structure was found to be a precursor for lattice unzipping 33 in a previous study by our group. We also investigated the structures obtained by hydrolyzing the isolated epoxy groups, with two hydroxyls per pre-existing epoxy group.…”