Electronic structure of oxidized nitrogen-doped graphene nanoflakes. Temperature dependence of paramagnetic response, aging and thermocycling

[Display omitted] •Electronic structure of oxidized nitrogen-doped carbon nanoflakes is studied.•Narrow and broad components are detected in absorption EPR spectra.•Narrow line follows Curie-Weiss law and it is attributed to localized electrons.•Broad line follows Pauli law and it is associated with mobile electrons.•Long-time storage and thermocycling does not significantly affect the structure. Being widely used in many applications the oxidized nitrogen-doped graphene nanoflakes (N-GNFox) are subjected to chemical composition change due to the aging, thermal and oxygen treatment. These processes were studied for the first time by electron paramagnetic resonance (EPR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The 3.5 years aging of the sample increased the oxygen and decreased the carbon contents, reduces the dispersion of atom around the paramagnetic centers and causes a change in the surrounding of the centers. The EPR spectra consist of the narrow and broad components which exhibit the Curie-Weiss and Pauli behaviors. The assignment of the EPR spectrum lines to localized and mobile electrons is discussed in connection with the temperature dependence of the intensity of paramagnetic response and conduction mechanism. The results of this work can be useful in explanation of the properties of carbon nanomaterials when used in modern devices and processes.