Magnetic Centres in Functionalized Graphene

Abstract

Discussion of the origin of paramagnetic centres observed by electron paramagnetic resonance in graphene oxide (GO) and reduced graphene oxide (rGO) is done on the assumption that GO can be considered as a functionalized graphene. This leads to the conclusion that the narrow signal with g close to 2, observed for GO and thermally reduced GO, is due to paramagnetic centres localized on defects and exchange coupled to conduction electrons. Randomness of graphene modication results in variety of parameters of EPR signals. The broad signals observed in GO and rGO and ascribed to magnetic clusters on the zig-zag edge states indicate that the edge magnetism can be preserved by functionalization.

EPR and Impedance Measurements of Graphene Oxide and Reduced Graphene Oxide

“…In our previous works concerning activated carbon fibers [2,3] and active carbon materials [15] EPR signals were almost the same as observed for RGO, with similar g values and temperature evolution. Three signals were ascribed to the three different paramagnetic centers: -line (1) from "pure" carbon (not in contact with adsorbed molecules), -line (2) from carbon interacting with molecules adsorbed at adsorption sites where adsorbed molecules get strongly immobilized at the surface, -line (3) from carbon at adsorption sites where adsorbed molecules show more "freedom" of rotational movements.…”

“…It is mostly due to their peculiar electronic properties, which are considered very promising from the point of view of many applications in electronics, spintronics, photovoltaics, energy storage, etc. Especially interesting is the fact that the pure graphene layer shows ballistic conduction [1], while introduction of defects causes the strong electron localization, which can even lead to the magnetism of graphene-based materials [2]. The main source of defects is obviously the edge of a layer, with the zig-zag conformation generating the localized states [3,4].…”

Preparation and characterization of partially reduced graphene oxide aerogels doped with transition metal ions

“…The EPR signals shape, intensity, g factor, linewidth, spin concentration is source of large number of information about local site symmetry, local dynamic and electron relaxation [50]. EPR study of graphene and graphene-related materials gives an important information about interactions and magnetism sources like defects, not passivated magnetic moments on edges, surface adatoms with unpaired magnetic moments, conduction electrons, and also remaining metal ion contamination [28,[51][52][53][54][55][56][57][58][59]. Unpaired electrons located on edges, on/in the graphene surface, are extremely sensitive to external conditions like atmosphere (oxygen, helium and vacuum) or moisture influencing the localization of Figure 7 Raman spectra of the reference and TMi-doped prGO aerogels.…”

Graphene oxide-multiwalled carbon nanotubes composite as an anode for lithium ion batteries

“…Graphene oxide (GO) was obtained from natural graphite by modified Hummers method [20] as it was described before [21]. Composite electrodes with typically 9 % of MWNTs were prepared by the direct mixing of GO and MWNTs in N-methylpyrrolidone (NMP) as it was described previously [22].…”