Raman study of D* band in graphene oxide and its correlation with reduction

Abstract Reduced graphene oxide (rGO) is a graphene-like material that exhibits high productivity for a wide range of industrial applications. To promote the application of rGO, it is important to not only produce high-quality rGO but also precisely evaluate the output. The intensity ratio of the D to G band in the Raman scattering is commonly used to assess the defect density of the carbon materials; however, this ratio is limited to evaluate the reduction degree of rGO because of the ambiguity arising from the superposition of the bands. In this study, we investigate the relationship between the intensity ratio of D* to G band and the reduction of graphene oxide (GO) to evaluate the degree of reduction of rGO. The spectral analysis of GO and rGO, along with systematic research of the thermally reduced GO synthesized via thermal treatment (100–900 °C) revealed a strong linkage between the D*/G intensity ratio and the C/O atomic ratio. The atomic vibrational relationships were elucidated by the assignment of the D* band, based on the density functional perturbation theory calculations. These findings explain the atomic vibrational properties of rGO and provide an indicator of the quality of rGO to optimize its performance for applications.