The correlation between electrical conductivity and second-order Raman modes of laser-reduced graphene oxide

Abstract

Raman spectroscopy is the tool of choice in the physicochemical investigation of carbon nanomaterials. However, Raman analysis of graphene oxide (GO) is lagging in comparison to the rich information gained in the case of carbon nanotubes and graphene. Here, we carried out a joint current sensing atomic force microscopy (CSAFM) and Raman spectroscopy investigation of laser-reduced GO. Reduced graphene oxide (rGO) was obtained under different laser powers in the range from 0.1 to 10 mW (532 nm). We compare the Raman spectra and the electrical conductivity at the nanoscale obtained by current sensing atomic force microscopy. Our analysis shows that three bands in the second-order region (2D, D + G, 2G), in the range from 2500 to 3200 cm⁻¹, are uniquely sensitive to the degree of reduction. Moreover, we found that the changes in peak area ratios A_D+G/A_D and A_2G/A_D show a direct correlation with the electrical resistance of rGO. We establish an optical micro-spectroscopy way to assess the degree of reduction in laser-reduced GO. These new insights provide a convenient and useful way to investigate the reduction of rGO from the fitting analysis of Raman spectra, becoming a useful tool in fundamental research and the development of rGO-based microdevices.