## 3 Results
### Effect of the Vitamin C (VC) Amount on Textural Properties and Hydrophobicity
A typical, strong peak at \(2\theta=11.6^{\circ}\), is the (001) plane of IGGO, with an interlayer spacing of 7.6 A. This large distance of interlayer could be linked to the presence of epoxy, hydroxyl, and carboxyl groups [40]. The (001) peak of rGOA-0 decreases, and a faint (002) facet of graphitic carbon appears at \(2\theta=25.3^{\circ}\)[41]. It proves that incomplete reduction occurs on the rGOA-0 nanosheets surface, which agrees with the SEM observations. After the reduction process, the XRD pattern of rGOA-1 has a (002) plane at \(2\theta=25.3^{\circ}\), suggesting ordered graphene layers and yielding a smaller interlayer spacing of 3.6 A. It could be claimed that due to the removal of the oxygen functionalities, C=C bonds and \(\pi\)-\(\pi\) interactions are restored, reducing the interlayer spacing [42]. Figure 2: Scanning electron microscopy (SEM) images of IGGO (**a**,**b**), rGOA-0 (**c**,**d**), and rGOA-1 (**e**,**f**). The Raman spectra of IGGO, rGOA-0, and rGOA-1 are given in Figure 4. Two characteristic bands, D band (1345 cm\({}^{-1}\)) and G band (1600 cm\({}^{-1}\)), represent the defects caused by sp\({}^{3}\)-hybridized carbon atoms and the stretching vibrations by sp\({}^{2}\) lattice carbon atoms in the graphene sheet, respectively [20]. The ratio of the intensity of the D and G bands (I\({}_{\rm D}\)/I\({}_{\rm G}\)), can be used as an important index of the lattice defect density in the carbon structure, having a positive correlation between the I\({}_{\rm D}\)/I\({}_{\rm G}\) ratio and the degree of defects [43]. The Raman spectra show that the I\({}_{\rm D}\)/I\({}_{\rm G}\) ratio obviously improves from 0.86 of IGGO to 1.03 of rGOA-1. High-defect populations are found in rGOA-1 flakes, which could be attributed to the strong reducing activity of VC, which results in the oxygen-containing functional groups also being removed, leaving vacancies in the original positions. The 2D bands located in the range of 2300-3100 cm\({}^{-1}\) are also a characteristic feature of carbon materials [21]. In the Raman spectra (Figure 4b), rGOA-0 and rGOA-1 demonstrate a wide and up-shifted 2D peaks, indicating a structure with few layers [44]. FTIR spectra of IGGO, rGOA-0, and rGOA-1 (Figure 5) exhibit characteristic absorption bands. The absorption band at about 3441 cm\({}^{-1}\) is attributed to the O-H stretching vibration of in the carboxyl groups, C-OH groups, and adsorbed-state water. It suggested that the carboxyl group was reduced to the hydroxyl group, possibly indicating an incomplete reduction of the IGGO. Several distinct peaks of IGGO are observed, such as C-H (at 2927 cm\({}^{-1}\), low-intensity stretching and bending vibrations), C=O (at 1727 cm\({}^{-1}\), stretching vibration of carboxyl groups), C=C (at 1600 cm\({}^{-1}\) and 1380 cm\({}^{-1}\), vibration of the graphene skeleton), and C-O-C (at 1050 cm\({}^{-1}\), stretching vibration of epoxy groups) [45; 46]. After the self-hydrothermal reduction of rGOA-0, the intensities of the peaks at 1727 cm\({}^{-1}\) (C=O stretching vibration) and 1050 cm\({}^{-1}\) (C-O-C stretching vibration) are weakened to a certain extent, illustrating that incomplete reduction takes place. Furthermore, for rGOA-1, the C=O peak at 1727 cm\({}^{-1}\) is absent, and the peak at 1050 cm\({}^{-1}\) (C-O-C stretching vibration) is absent. Figure 4: Raman spectra of IGGO, rGOA-0, and rGOA-1 (**a**) and up-shift 2D peaks in Roman spectra of rGOA-0, and rGOA-1(**b**). Figure 3: X-ray diffraction (XRD) patterns of IGGO, rGOA-0, and rGOA-1. tion) become very weak, indicating that the carbonyl group is completely reduced, and nucleophilic substitution occurs between the epoxy group and VC [43]. According to the experimental results described above, the possible working mechanism is suggested, as shown in Figure 6. Under hydrothermal conditions, the carboxyl group on IGGO is reduced to the hydroxyl group by VC, and the epoxy bond dehydates the water molecule by nucleophilic ring-opening, restoring the C=C conjugate system.