In this study, we report the synthesis of high purity reduced graphene oxide (rGO) from pristine graphite via a fast and cost-effective one-step ultrasonic reduction method. Ultrasonic treatment was employed to avoid the harsh reaction conditions, including high temperature and use of highly toxic hydrazine, required for the conventional rGO preparation method. The high temperature produced during the ultrasound irradiation at low temperature and short reaction time enabled the reduction of graphene oxide (GO) into rGO without the use of toxic chemicals. The oxygen functional groups on GO were successfully reduced by the sonochemical reduction. The rGO prepared using the ultrasonic method exhibited a curled morphology, a very thin wrinkled paper-like structure, sheet folding, minimal layers (similar to 4 layers), and a layer spacing of similar to 1 nm. The sonochemical approach for the synthesis of rGO showed fast, high productivity, much improved safety, less energy, and time consuming characteristics as compared to other methods. More importantly, highly explosive and poisonous hydrazine is not required in this sonochemical technique, opposed to that required in conventional rGO synthesis, making it useful for many industrial applications of rGO. (C) 2016 Elsevier Inc. All rights reserved.