“…Figure 1 shows the XRD pattern of CuO NPs, which showed the presence of characteristic peaks at 2θ values of 32.9°, 33.5°, 35.9°, 39.1°, 42.3°, 49.1°, 54.9°, 58.7°, 61.9°, 66.5°, 68.4°, 72.8° and 75.5°, related to (110), (1 ̅ 10), (1 ̅ 11), ( 111), (1 ̅ 12), (2 ̅ 02), ( 020), ( 202), (1 ̅ 13), ( 022), (3 ̅ 11), ( 311) and (2 ̅ 22) planes for both the conventional and green CuO, respectively, which can be indexed on the basis of monoclinic tenorite CuO with the C2/c space group (JCPDs file No. 01-080-1916) [36], indicating the good crystallinity of the prepared CuO NPs and the absence of any characteristics peaks of any other phase of CuO. Moreover, there were few unidentified diffractions peaks at 2θ values less than 20°; especially for the conventional CuO, which could not be assigned to any copper-based compound and were considered as impurities.…”