## 3 Results and Discussion  
### Characterization of the Photocatalytic Nanocomposites  
#### 3.1.1 Raman Spectroscopy  
The Raman spectra of all the photocatalysts synthesized via the hydrothermal method are presented in Figure 1. The characteristic peaks of OLNCs are represented by the D band (1352 cm\({}^{-1}\)) and the G band (1599 cm\({}^{-1}\)). These peaks can be seen from all the composite (TiO\({}_{2}\)/OLNCs) material, and not for the pure TiO\({}_{2}\). Characteristic peaks for pure TiO\({}_{2}\) can be seen at positions 653, 538, 404, and 218 cm\({}^{-1}\)--they correspond with the presence of the anatase phase TiO\({}_{2}\)[17]. The aforementioned peaks appear in all the composite (TiO\({}_{2}\)-OLNC) materials but not the clean OLNCs.  
It is notable that the D band, G band, and the TiO\({}_{2}\) peaks shifted towards the lower frequency--an indication of tensile stress, as the TiO\({}_{2}\) interacted with the functional groups of the OLNCs [18]. The presence of the anatase phase TiO\({}_{2}\) was confirmed by the PXRD data (see Supplementary Figure S1) [19].  
XPS data for the TC-10 material also showed the presence of TiO\({}_{2}\) (see Supplementary Figure S2 and Table S1) [20]. XPS survey spectra show all the characteristic peaks of a TiO\({}_{2}\)-carbon composites material, with peaks at 284.7 eV (C1s), 531.1 eV (O1s), and 458.9 eV (Ti\({}_{2p}\)) (Figure S2a). This indicates that the elemental composition of the photocatalyst consists of C, O, and Ti [3]. The XPS data were deconvoluted and the C, Ti, and O spectra are shown in Figure S2b, S2c, and S2d, respectively. The deconvoluted peak positions and intensities are given in Table S2. The Ti peak occurs at 458.9, corresponding to Ti in oxidation state 4\({}^{+}\), typical of a Ti-O bond. No indication of Ti-C bonding was observed (or expected). The C peak region showed the presence of C=C (13.9%), C-C (32.8%), and C-O/C=O (9.8%) bonds. The XPS O spectral region showed that O was in different environments typical of C=O (6.3%), (C-O) (6.7%), and TiO\({}_{2}\) (8.3%Ti; 17.3% O)). These results agree with the Raman and PXRD data, and are consistent with the synthesis of a TiO\({}_{2}\)-OLNC composite.  
Therefore, in this study, we have successfully synthesized a TiO\({}_{2}\)-ONLC nanocomposite.  
Figure 1: Raman spectra for all photocatalysts.  
3.1.2. Thermogravimetricmetric and Differential Thermal Analysis  
Figure 2 shows the thermal decomposition steps for the photocatalysts, as the mass of the OLNCs was increased from 10 to 50 mg. From Figure 2a, two major weight loss steps can be seen for all the materials. The first weight loss took place at around 100 \({}^{\circ}\)C, and can be attributed to the evolution of moisture, which contributed 3% to 6% (TC-50, 5%; TC-30, 3%; TC-20 4%; TC-10; 6%) of the weight loss for the respective photocatalysts. The second major weight loss took place at 478 \({}^{\circ}\)C (TC-50), 480 \({}^{\circ}\)C (TC-30), 561\({}^{\circ}\) (TC-20), and 500 \({}^{\circ}\)C (TC-10), corresponding to 36%, 27%, 25%, and 13% weight loss for the respective materials, and can be attributed to the decomposition of organic material due to the carbon oxidation process [6]. The DTA thermograms give a clearer picture of the decomposition steps that all the nanocomposites underwent (Figure 2b). The remaining residue was TiO\({}_{2}\), and the analysis data confirmed the approximate TiO\({}_{2}\)/OLNC ratios. The composites with the lower OLNCs content (TC-20 and TC-10) showed higher thermal stability than the composites with higher OLNCs content. However, pristine OLNCs (from our previous study) showed higher thermal stability (ca. 650 \({}^{\circ}\)C) than the as-synthesized TiO\({}_{2}\)/OLNCs [14]. The hydrothermal treatment in the presence of NaOH affected the thermal stability of all of the nanocomposites [21].