A comparative study on few-layer graphene production by exfoliation of different starting materials in a low boiling point solvent

Abstract

Three different graphite-based powders (expandable graphite and two different nano-graphite powders) were investigated as starting materials for an effective liquid phase exfoliation process in isopropyl alcohol (IPA). The prepared dispersions were analyzed and compared in terms of their graphene concentration, stability, number of graphene layers and quality, as well as the electrical conductivity of the prepared graphene-based materials. Good quality graphene dispersions (I-D/I-G < 0.3) with a relatively high concentration (similar to 1.1 mg/ml) were prepared in IPA within 90 min sonication time by utilizing a high specific surface area (similar to 175 m(2)/g) nano-graphite powder derived from natural graphite. Transmission electron microscope analyses of this sample revealed mostly folded and scrolled few layer graphene (FLG) sheets (<5 layers) entangled each other. The electrical conductivity of the thin film prepared from this dispersion was similar to 15 and 86 S/m, before and after annealing, respectively. FLG prepared from expanded graphite, obtained by thermal treatment of expandable graphite, exhibited both much higher quality (I-D/I-G < 0.09) and electrical conductivity (similar to 2104 and 19,200 S/m before and after annealing, respectively) when dispersed in IPA for 90 min. However, the graphene-based material concentration of the prepared dispersion was relatively low (similar to 0.06 mg/ml)