For the first time, this work reports a facile sonochemical route in the synthesis of graphene oxide nanosheets (GO) via oxidation of graphite (G). The synthesis of GO was carried out in a fast way under ultrasonic bath irradiation (GO-U). In comparison, the synthesis of GO via classical method (GO-C) was done under the same conditions as ultrasonic method. The products were completely different and the oxidation did not happen the same as way as ultrasonic method. Furthermore, GO was synthesized based on classical approach that most commonly used (GO-C'), not under the same conditions as ultrasonic method. The GO sheets were characterized using UV-Vis, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), transmission electron microscope (TEM), thermal gravimetry (TG), and Raman spectroscopy techniques. The XRD confirms that the spaces between GO-U and GO-C' sheets were higher than graphite. Also, XRD indicated that the GO-U has fewer sheets rather than GO-C'. The TEM observations were confirmed the synthesis of nanosheets. The UV-Vis results were shown the absorption peaks at 230 nm for GO-U and GO-C', at 245 nm for GO-C, and at 255 nm for G. The blue shift in GO-U with respect to G and GO-C can be interpreted based on the higher character of sp(3)/sp(2) in GO-U than G and GO-C. The FT-IR presents the oxygenated functional groups on graphene oxide sheets. A reduction in size of the in-plane sp(2) domains was observed by Raman spectrum. The BET analysis for G, GO-U and GO-C' confirmed that GO-U has a highest specific surface area among all the samples. Therefore, the ultrasonic bath method even with low intensity has a fundamental role in the synthesis of graphene oxide nanosheets and it is relatively fast, simple, cost-effective and efficient as compared to the classical method. (C) 2014 Elsevier Inc. All rights reserved.