C1s XPS of GO and nanoscale GO sheets. (a) GO before cutting reaction; (b) nanoscale GO after cutting reaction. The peaks 1, 2, 3, and 4 correspond to C=C/C-C in aromatic rings, C-O (epoxy and alkoxy), C=O, and COOH groups, respectively.
Wang et al. Nanoscale Research Letters 2013 8:226 doi:10.1186/1556-276X-8-226