# Catalytic Degradation of Anionic Organic Dye on Greenly Synthesized CuO/ZnO Nanocomposites
## 3 Results and Discussion  
Figure 1 shows the FTIR of ANE, Z, 1C3Z, 1C1Z, 3C1Z, and C nanocomposites before (a) and after hydrothermal treatment and calcination (b). The ANE spectrum contains more than five peaks, indicating that it is not a simple chemical, and it has some common peaks with the nanocomposites. Before hydrothermal treatment (Figure 1a), all nanocomposites have the same pattern with a broad peak in the range of 3200-3400 cm\({}^{-1}\), which indicates a hydrogen bond. This band indicates the existence of hydroxyl (-OH) and (H\({}_{2}\)O) adsorbed on the surface [21]. The other common peak at 1620 cm\({}^{-1}\) is related to the hydroxyl group (-OH). The small peak at around 2100 cm\({}^{-1}\) can be related to the absorption band of C\(\equiv\)C [21]. After hydrothermal treatment and calcination, the intensity of the peaks at 3200-3400 cm\({}^{-1}\) and 1620 cm\({}^{-1}\) become very weak due to the conversion of metal hydroxide into metal oxide and due to the dehydration of the surface during the calcination process. In Figure 1b, the appearance of the peaks below 700 cm\({}^{-1}\) after hydrothermal treatment confirms the successful conversion of metal hydroxide into metal oxide, since this band is related to the metal-oxygen bonds in both ZnO and CuO. Figure 2 shows the XRD patterns for the five prepared nanocomposites. Lines 1, 3, 5, 7, and 10 located at 20 \(\sim\) 31.96\({}^{\circ}\), 34.61\({}^{\circ}\), 36.44\({}^{\circ}\), 47.74\({}^{\circ}\), and 56.73\({}^{\circ}\) represent the diffraction planes (1 0 0), (0 0 2), (1 0 1), (0 1 2), and (1 1 0), respectively, of the ZnO hexagonal structure (Card no. 96-900-4179). The intensity of these peaks decreased by decreasing the zinc precursor in the synthesis mixture, and disappeared in sample C, which represents pure CuO. Lines 2, 4, 6, 8, and 9, passing through the peaks at 20 \(\sim\) 32.47\({}^{\circ}\), 35.60\({}^{\circ}\), 38.90\({}^{\circ}\), 48.96\({}^{\circ}\), and 53.576\({}^{\circ}\), correspond to planes (1 1 0), (1 1 1), (1 1 1), (2 0 2), and (0 2 0), respectively, of tenorite copper oxide with a monoclinic phase (Card no. 96-721-2243). The intensity of the monoclinic tenorite copper oxide peaks increases gradually, by the increase in copper precursor in the synthesis mixture, according to Table 1.  
Figure 1: FTIR spectra of ANE, Z, 1C3Z, 1C1Z, 3C1Z, and C greenly prepared before (**a**) and after hydrothermal treatment (pH = 10, T = 250 \({}^{\circ}\)C, t = 2.5 h) and calcination for 2 h at 300 \({}^{\circ}\)C (**b**). Figure 2: XRD patterns of Z, 1C3Z, 1C1Z, 3C1Z, and C greenly prepared via hydrothermal route (pH = 10, T = 250 \({}^{\circ}\)C, t = 2.5 h) and calcination for 2 h at 300 \({}^{\circ}\)C.  
The crystallite sizes of ZnO and CuO were measured using the Debye-Scherrer equation and are reported in Table 2. The main peaks of the plane (101) of ZnO and plane (111) of CuO were used to estimate the crystallite size of ZnO and CuO, respectively. The crystallite sizes of pristine zinc oxide and pristine copper oxide were 26 and 29 nm, respectively. It is clear from Table 2 that, when the starting mixture contained 25% of a copper precursor, the crystallite size of ZnO increased to 30 nm. By a further increase in the copper precursor to 50% and 75%, the crystallite size of ZnO decreased to 21 and 17 nm, respectively. However, adding ZnO to the starting synthesis mixture always resulted in a lower crystallite size of CuO and for any composition, as shown in Table 2. In addition to this qualitative evidence for the presence of both CuO and ZnO in the prepared nanocomposites, another qualitative analysis was performed for each sample; the compositions are shown in Table 2. It is apparent that the tendency of CuO for formation is higher than that of ZnO under the conditions used in this work. For example, sample 3, which was prepared with a 1:1 ratio of the precursors of both metal oxide. However, the final nanocomposite contains 69.3% of CuO and 30.7% of ZnO.