## 3 Results and Discussion
### Characterization of Photocatalyst
The nanocomposites have a higher intensity ratio compared to GO indicating higher graphene structural disorder upon binding onto TiO\({}_{2}\)[43]. The interactions of Ti-O-C bands could be the reason for increasing sp\({}^{3}\) defects in nanocomposites [42]. The intensity ratios between D and G bands were utilized to determine the crystal size parallel to basal planes (\(L_{\text{a}}\)), using the equation of Tuinstra, where the coefficient 38.5 was for wavelength at 633 nm [44]:  
\[L_{\text{a}}(\text{nm})=\frac{38.5}{\text{I}_{\text{D}}/\text{I}_{\text{G}}} \tag{4}\]  
The recalculated values of \(L_{\text{a}}\) are shown in Table 1. The La values decreased from GO over rGO to the prepared nanocomposites. It could be concluded that prepared nanocomposites had decreased sp\({}^{2}\) domains in the structure [31]. XRD patterns of pure graphite and synthesized GO are given in Figure 3A. Both of these materials had characteristic X-ray diffraction peaks. The pure graphite showed characteristic peaks at 26.48\({}^{\circ}\) and 54.58\({}^{\circ}\) attributed to the (002) and (004) planes. In particular, the diffraction peak of GO located at 10.68\({}^{\circ}\) corresponded to the (001) plane. On the XRD pattern of rGO, after the reduction method of GO, a new and wide diffraction peak located at 24.40\({}^{\circ}\) attributed to the (002) plane appeared. The (002) plane in rGO indicates that the most oxygen-containing groups such as O-H, C=O, and C-O were removed from the nanomaterials. The new diffraction peak confirmed the successful conversion of GO into rGO (inset of Figure 3A) [44; 45; 46]. XRD patterns of pure TiO\({}_{2}\) and prepared nanocomposites \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Samples ID** & **D-Band, cm\({}^{-1}\)** & **Ip** & **G-Band, cm\({}^{-1}\)** & **I\({}_{\text{G}}\)** & **I\({}_{\text{D}}\)/I\({}_{\text{G}}\)** & **L\({}_{\text{a}}\), nm** \\ \hline GO & 1329 & 42 & 1585 & 95 & 0.44 & 87.5 \\ rGO & 1347 & 77 & 1593 & 99 & 0.78 & 49.4 \\ TiO\({}_{2}\)+rGO (5\%) & 1345 & 302 & 1605 & 381 & 0.79 & 48.7 \\ TiO\({}_{2}\)-rGO (15\%) & 1341 & 138 & 1601 & 154 & 0.90 & 42.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Raman intensity and shift of the prepared GO, rGO, and TiO\({}_{2}\)@rGO nanocomposites. Figure 2: Raman spectra of (**A**) the respective nanocomposites, (inset shows TiO\({}_{2}\) calculated at 300 \({}^{\circ}\)C); and (**B**) GO, rGO, and the respective nanocomposites. The inset shows the characteristic D and G bands of graphene-based materials. are shown in Figure 3B. The pure TiO\({}_{2}\) nanoparticles had diffraction peaks at 25.30\({}^{\circ}\), 37.86\({}^{\circ}\), 47.98\({}^{\circ}\), 53.94\({}^{\circ}\), 55.06\({}^{\circ}\), 62.62\({}^{\circ}\), 68.68\({}^{\circ}\), 70.18\({}^{\circ}\), and 75.12\({}^{\circ}\) and were indexed to the (101), (103), (004), (200), (105), (211), (204), (116), (220), and (215) plane, respectively [37]. Specified diffraction peaks correspond to the anatase-phase of TiO\({}_{2}\) nanoparticles. As can be seen in Figure 3B pure TiO\({}_{2}\) nanoparticles and both nanocomposites show only anatase-phase peaks in the X-ray diffraction patterns. This could be a consequence of the overlapping of the powerful intensity of the anatase-phase peak at 25.30\({}^{\circ}\) and the low diffraction peak of the rGO at 25.40\({}^{\circ}\)[46; 47]. Nevertheless, we noticed that the diffraction intensities of anatase peaks decreased in both nanocomposites, in particular the diffraction peak at 25.30\({}^{\circ}\). The reason for that can be in an increasing amount of GO with defects in carbon atoms. XPS was performed in order to analyze the elemental composition and chemical environment of the elements detected at the surface of the prepared nanocomposite materials. Figure 4A shows a comparison between the high-resolution C 1s spectra of the different samples. The C 1s spectrum of GO shows the expected shape for this nanomaterial, with two intense peaks and a tail at higher BE.