21–1272) with lattice constants a = 3.78 Å and c = 9.50 Å [39, 40]. Crystal facet (101) was the main crystal structure of the anatase TiO2 due to its maximum peak intensity. No rutile phase was detected due to the low reaction

temperature employed in this work. The average crystal size of the TiO2 nanoparticles in the composite was calculated to be ca. 8.1 nm based on Scherrer’s equation. No diffraction peaks from impurities and other phases could be detected, thus indicating that the product was pure and well see more crystallized. Notably, the typical diffraction peaks of graphene or GO were not found in the XRD pattern of the composite. A possible reason for this observation was that the most intense diffraction peak of graphene (2θ = 24.5°) [41] could be shielded by the main peak of anatase TiO2 at 25.3°. Figure 4 XRD spectra of (spectrum a) graphite oxide and (spectrum b) rGO-TiO 2 composite. Figure 5 shows the FTIR spectra of graphite powder, graphite oxide, and the rGO-TiO2 composite. While no significant peaks were observed in raw graphite, graphite oxide was found to exhibit several characteristic absorption bands of oxygen-containing groups (Figure 5, spectrum b). The absorption peaks included 870 cm−1 for aromatic C-H deformation [42], 1,052 cm−1

for C-O stretching [21], Talazoparib clinical trial 1,220 cm−1 for phenolic C-OH stretching [42], 1,625 cm−1 for the hydroxyl groups of molecular water [43], 1,729 cm−1 for C = O stretching [20], and a broad peak at 3,400 cm−1 for the O-H stretching vibrations of C-OH groups [44]. The small peaks at 2,854 and 2,921 cm−1 in the spectrum were attributed to the CH2 stretching vibration [45]. Figure 5 (spectrum c) shows the FTIR measurement for the rGO-TiO2 composite. It can be observed that the intensities of absorption bands of oxygen-containing functional groups such as C-O (1,052 cm−1) were dramatically reduced. The C-OH and carbonyl C = O Rebamipide bands at 1,200 and 1,729 cm−1, respectively, were also found to have disappeared for the rGO-TiO2 composite. However, it can be seen that

the spectrum retains a broad absorption band centered at 3,400 cm−1, which was attributed to the residual O-H groups of rGO. These results implied that GO was not completely reduced to graphene through the solvothermal treatment but was instead partially reduced to rGO, which possessed residual oxygen-containing functional groups. Therefore, TiO2 could be susceptible to interactions with these functional groups in the nanocomposites [45]. The spectrum also showed strong absorption bands at 450 and 670 cm−1, indicating the presence of Ti-O-Ti bond in TiO2[46]. Figure 5 FTIR spectra of (spectrum a) graphite powder, (spectrum b) graphite oxide, and (spectrum c) rGO-TiO 2 composite. UV-visible (UV–vis) spectroscopy has been proven to be an effective optical characterization technique to understand the electronic structure of semiconductors.