Figure 2: (a) SEM image of CuO nanofibers obtained after calcination. ((b) and (c)) Magnified images of (a). (d) Nanofibers changing to NPs’ clusters after sonication in water. (e) XRD spectrum of CuO NPs. (f) EDS spectrum and quantitative results of CuO NPs (the longest peak in EDS spectrum corresponds to Si, which was used as a substrate for collecting nanofibers and its contribution was excluded from the quantitative results).