Experimental comparison between graphene and reduced graphene oxide along with significant conversion of rGO from n-to p-type

We demonstrate an efficient and non-explosive method for synthesizing graphene and reduced graphene oxide (rGO). To enable the use of both materials in broad electronic applications, a large-scale production method with controllable electrical properties must be needed. In the current state of graphene oxide preparation, Hummers method is the most widely used. In this method, NaNO₃ produces toxic gases during the reaction, and hence, this method is not recommended for the large-scale production. Here, we adopted the liquid-phase exfoliation and Improved Hummers method to produce graphene and GO since it eliminates the use of NaNO₃ and its toxicity. We introduced a pre-cooling procedure to reduce the explosive nature of the extremely exothermic reactions. This method yields more oxidized graphene compared to Hummers’ method. We experimentally compared the structural, electrical, and thermal transport properties of both the materials. Characterization techniques such as X-ray diffraction, FTIR, and optical microscopy reveal the high quality of graphene and rGO. Here, we also report the results on the conversion of rGO from n-type to p-type. It was found that graphene behaves as p-type material, whereas rGO behaves as an n-type up to an annealing temperature of 350 °C, while after 600 °C, it is converted to a p-type material. These results demonstrate that thermal annealing treatment drastically varies the carrier properties of rGO, allowing it to be used in various applications, including flexible thermoelectrics. A high-yield production of graphene and rGO could be beneficial from this improved synthesis.