Fourier transform infrared (FTIR) spectra were obtained to confirm the presence and identify more precisely of oxygen functionalities on the surface of GO (Figure ). FTIR spectroscopy revealed a broad band between 3000 cm -1 and 3700 cm -1 , corresponding to O-H stretching vibrations characteristic of adsorbed water molecules, hydroxyl and carboxyl groups . A minor feature around 2815 cm -1 could be attributed to the presence of aliphatic C-H stretching vibrations . In contrast, a sharp peak around 1725 cm -1 indicated the presence of carbonyl and carboxyl groups by C=O stretching vibrations . The contribution of the cyclic aromatic networks is shown by the presence of weak peaks in the 1550-1620 cm -1 region corresponding to in-plane vibrations ; however, the potential contribution of the O-H bending mode of residually adsorbed water molecules, which could be identified around 1625 cm -1 should not be excluded . A strong absorption band around 1400 cm -1 could be assigned to O-H bending vibrations in hydroxyls . Furthermore, the presence of ethers is described by intense absorption bands around 1045 cm -1 and 965 cm -1 , which correspond to C-O stretching vibrations , with epoxides in particular exhibiting C-O bending vibrations around 850 cm -1 . All 3 GO materials exhibited similar FTIR spectra, with minor differences observed particularly in the us-GO sample (Figure ). Besides a lower intensity of the band around 1725 cm -1 , us-GO also presented a less pronounced band around 1195 cm -1 , which could be attributed to C-O stretching in phenols .