Few-layer-graphene with high yield and low sheet resistance via mild oxidation of natural graphite

Abstract

The mild oxidation of natural graphite was obtained via the modified Hummers method by employing an oxidation temperature of 20 °C and KMnO₄ loading of 2 g, while the degree of mild oxidation was controlled by varying the oxidation time from 30 to 60, 90 or 120 min. The mild oxidation of graphite was demonstrated by X-ray diffraction (XRD), along with UV-vis spectroscopy, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Then, MOG (mildly-oxidized graphite) was grafted with aryldiazonium salts of sulfonic acid (ADS) to afford good water dispersion, followed by sonication exfoliation and centrifugation to isolate the few-layer-graphene (FLG). The FLG was characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM) and Raman spectroscopy, and its sheet resistance (R_s), yield and water dispersion stability were also evaluated. The obtained FLG had low R_s (3 × 10² to 5.8 × 10⁴ Ω □⁻¹), high yield (19–85%), and good stability in water (79–86% after 4 week aging).