The deconvolution of the C1s XPS spectrum of GO showed a considerable degree of oxidation at the binding energy of 286.5, 287.6 eV, as observed in Fig. 5D; the peak at the binding energy of 286.5 eV is attributed to the CAO and CAOAC in the hydroxyl or epoxy groups; the peak at 287.6 eV was assigned to the OAC@O oxygen containing a carbonaceous band [41,42].