Optical properties of CuO/ZnO composites prepared by mechanical grinding

•CuO/ZnO composites were prepared by mechanical grinding.•The UV emission intensity is greatly reduced for the CuO/ZnO composites.•The red-shift of the UV emission peak is observed for the CuO/ZnO composites.•The absorption in the visible range of the CuO/ZnO composites is enhanced compared with pure ZnO. In this work, ZnO and CuO were first prepared by thermal evaporation and direct precipitation, respectively, and then CuO/ZnO composites were obtained by mechanical grinding the mixtures of CuO and ZnO. Scanning electron microscopy, Raman spectroscopy, Raman imaging, UV–vis absorption spectroscopy, and photoluminescence spectroscopy were used to analyze the morphology, structure, and optical properties of CuO/ZnO composites. Raman spectra suggest that the prepared ZnO has a high crystalline quality, while the CuO/ZnO composites have an internal stress. Compared with ZnO, the absorption edge of CuO/ZnO composites shows a red-shift, and the absorption intensity in the visible region is increased greatly. Pure ZnO shows a strong ultraviolet (UV) emission and a weak green emission. As for the CuO/ZnO composites, with the increase of CuO content, the intensity of the UV emission is gradually reduced and the UV peak is gradually moving towards the longer wavelength direction. The decrease in the UV emission intensity should be attributed to interface effects, and the red-shift of UV emission peaks may be caused by unintentional Cu-doping.