The intensity ratio of the D to G peak (ID/IG) is an indication of the degree of defects in graphene-related materials where the intensity of the D band is related to the disordered structure of the sp2 lattice [13]. For example, pristine graphite which has the lowest disorder density in the sp2 lattice gave a ratio of 0.23, while thermally reduced graphene oxide which has the

highest disorder density gave a ratio of 1.35 AZD9291 clinical trial [13]. In this work, the ratio of the ID/IG peak for ERGO is 1.03, while the ID/IG peak for GO (measured from the nearest baseline) is 1.02. This result is in accordance check details with previous reports of 1.08 and 1.05 for ERGO and GO, respectively [13]. This result indicates that GO reduction to ERGO did not increase the defect density significantly. It can be suggested that the sp2 lattice was maintained even after reduction of GO to ERGO and this is also in accordance with the FTIR of ERGO

where the sp2-hybridized C=C bonds are still present in ERGO at around 1,610 cm-1. In order to prove that ERGO is the result of electrochemical reduction of GO in 6 M KOH by voltammetric cycling, GO films were immersed in deoxygenated 6 M KOH solutions for 1 h and 4 days at room temperature. Figure 3a,b shows the FTIR of GO immersed in deoxygenated 6 M KOH for 1 h and 4 days, respectively. The distinct differences shown in these figures and FTIR of pure GO are the disappearance of the C=O peak at 1,730 cm-1 and the appearance of two strong new peaks at 1,598 and 1,368 cm-1 (for a 1-h immersion) and 1,584 and 1,374 cm-1 (for a 4-day immersion). Both peaks (1,598 and 1,584 cm-1) and (1,368 and 1,374 cm-1) are attributed to the carboxylate COO- group, which has strong vibrations at 1,610 to 1,550 cm-1 and 1,420 to 1,300 cm-1[28, 29]. The presence of the COO- ion is due to the reaction between KOH and the acidic COOH groups in GO. It should be noted that the peaks PLEK2 due to COO- are stronger

than the peak due to OH vibration at 3,400 cm-1 in the FTIR spectrum of GO immersed in KOH. This is in contrast to the pure GO spectrum where all the peaks are relatively weaker than the OH peak. The complete disappearance of the C=O peak in the FTIR spectrum of GO immersed in KOH also shows that the peak at 1,730 cm-1 (C=O) is solely due to the carboxylic COOH group in GO. This also proves that the COOH groups in GO were not reduced to aldehyde HC=O and ketone C=O groups during immersion in 6 M KOH solution. The peaks for the C-OH stretching at 1,218 cm-1, OH bending of C-OH at 1,424 cm-1, stretching of the sp2-hybridized C=C bond at 1,625 cm-1 are no longer visible due to the strong vibration of the COO- group in the FTIR spectrum of GO immersed in the KOH solution.