Influence of N-doping on the structural and photoluminescence properties of graphene oxide films

Nitrogen (N) was doped into graphene oxide (GO) films at temperatures of 600–900 °C under the flow of a mixture of NH₃ and Ar. The N (atomic) concentration was varied in the range of 3.63–7.45%. XPS and FTIR spectra show that there are mainly single C–N and double CN bonds in the GO sheet. Raman spectra indicate that the G band becomes closer to the position of the G band of graphite with increasing doping temperature, and thus reveal that N doping produces a blue-shift of the G-band. In room-temperature photoluminescence (PL) spectra, N-doping produces an increase not only in the overall PL intensity, but also in the wavelength of the peak maxima. The shift of the induced PL of N-doped graphene is attributed mainly to the increased number of graphitic (or quaternary) N.