Graphene has extraordinarily high charge-carrier mobility values. Reduced graphene oxide, in contrast, has a much lower electrical conductivity. This is due to defects that are introduced during the oxidative synthesis of graphene oxide and cannot be “healed” by the following chemical reduction. For electronic applications, the carrier mobility and thus, the quality of the graphene is very important. So far, there had been no correlation between transport properties and the density of defects, in particular in the relevant range of defect density (about 0.2 % to 1.5 %). Reduced graphene oxide with this defect density can be produced on a multi gram-scale.

Siegfried Eigler, Freie Universität Berlin, Germany, and colleagues have prepared field-effect transistors based on single layers of graphene which were generated from oxo-graphene (pictured right) and determined the mobility values of charge carriers at room temperature. The team found mobility values of 0.3–33 cm² V^–1 s^–1. These values are inversely proportional to the density of defects. The team used almost defect‐free graphene (pictured left) prepared via tape exfoliation as reference samples. This type of graphene reaches much higher mobility values of 685 cm² V^–1 s^–1.

The results demonstrate the importance of knowing the quality of the graphene generated from its oxidized counterpart. The mobility of charge carriers can vary by orders of magnitude, although the density of defects varies only a little. This could explain the diverging results reported for reduced graphene oxide used in a range of applications.

• Room‐Temperature Transport Properties of Graphene with Defects Derived from Oxo‐Graphene,
  Zhenping Wang, Qirong Yao, Siegfried Eigler,
  Chem. Eur. J. 2020.
  https://doi.org/10.1002/chem.201905252