Contrasting Magnetic Properties of Thermally and Chemically Reduced Graphene Oxide

Abstract

We report the observation of enhanced magnetization in graphene oxide (GO) after thermal annealing. We have also proposed that this enhancement in magnetization is due to the increased density of zigzag edges. We conjecture that on annealing the random epoxy groups in the native GO migrate over the GO surface by acquiring thermal energy and self-assemble to form several long chains of epoxy groups. Subsequently, upon thermal reduction the GO sheet is unzipped along these long chains giving rise to more zigzag edges, resulting in enhancement of magnetization. We also found out that the density of epoxy groups plays an important role in the unzipping process. If the density of epoxy groups is low, then unzipping of GO is not possible. Chemical reduction of GO does not favor unzipping.

Visualizing chemical states and defects induced magnetism of graphene oxide by spatially-resolved-X-ray microscopy and spectroscopy

“…These results reveal that the PT-reduction of GO to M-rGO removed a proportion of oxygen-containing and hydroxyl groups from both flat and wrinkle regions of the GO surfaces. As further PT-reduction yielded H-rGO, the intensities of the features associated with the oxygen-containing and hydroxyl groups in the wrinkle and flat regions, and specifically of features C 2 (C-OH) and C 3 (C-O-C), which are presumed to have a major role in inducing the magnetic moment in GO or rGO as mentioned elsewhere 21 22 23 24 25 26 , were not significantly reduced. Even H-rGO exhibits more intense features C 3 (C-O-C) and C 4 (C=O) than does GO in the flat regions.…”

“…They further proposed that the presence of two hydroxyl groups bound to non-neighboring carbon atoms that are separated by one carbon atom favors the magnetic moment in GO. However, Bagani et al 26 presented opposing arguments for various magnetism between GO and rGO, the density of wrinkles in the GO sheet decreased upon chemical reduction at high temperature (600 °C) owing to the removal of many epoxy groups, increasing the number of zigzag edges/edge states, causing rGO to have greater magnetism than GO. The increase in magnetic moment is due to the increase in the number of zigzag edges/edge states after annealing of GO, which are stable with the same spin to minimize the Coulomb repulsion energy.…”

Polyacrylate grafted graphene oxide nanocomposites for biomedical applications

“…Extensive literature reports suggest that the not only the deoxygenation itself but its underlying process i.e. hydrazine 52 , thermal 53 or Birch 54 reduction strongly influences the magnetic properties of the resulting r-GO. In our case, the strong reducing agent, hydrazine hydrate, introduces significant defects and nitrogen dopants into the r-GO graphitic lattice which generates localised magnetic moment.…”

Preparing dangling bonds by nanoholes on graphene oxide nanosheets and their enhanced magnetism

“…23 Takaaki Taniguchi et al 24 used the photo reduced graphene oxide. Kousik Bagani et al 25 also reported the random epoxy groups in the native GO to investigate the relationship between the magnetization of the GO sheet and the defects of hydroxyl groups, C-H bonding, carbon vacancies 24 and epoxy groups 25 on the graphene nanosheets. Blonski Piotr et al veried that N-doping GO had high magnetization of ca.…”