Laser ablation synthesized ZnO, CuO and ZnO:CuO nanomaterials: A comparative study of structural, optical and antibacterial performance

The synthesis of ZnO and CuO as well as ZnO:CuO nanoscale, is described in this paper using the laser ablation method. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV-Vis spectroscopy were applied to validate the characterization performed on the produced ZnO, CuO, and ZnO:CuO nanoparticles. The XRD characteristics show that ZnO diffraction peaks were detected at 2θ angles of 31.55°, 34.19°, 36.03°, 56.42°, and 62.80° as well, which can be interpreted as a hexagonal wurtzite structure. On the other hand, CuO had peaks at 35.39°, 38.71°, 48.33°, and 61.50°, which confirmed the presence of a monoclinic structure. The ZnO:CuO nanocomposite exhibited peaks originating from both materials, indicating the proper integration of CuO into its structure. For CuO, elevated strain due to lattice distortion also came during the analysis, meaning ZnO had a significantly lower strain compared with CuO, pointing to better structure stability. With AFM results, we found out that ZnO films had an average grain size of 67.74 nm and surface roughness (Ra) of 2.572 nm, while CuO films had a larger average grain size of 85.65 nm and a Ra of 43.27 nm. Compared with the ZnO:CuO composite, the grain size was decreased to 39.29 nm, and the roughness increased to a Ra of 42.26 nm. According to the optical properties, ZnO bands have a band gap of 3.18 eV, CuO has a narrower 2.76 eV band gap, and this composite has a band gap of 2.98 eV with intermediate separation. Antimicrobial studies revealed that ZnO:CuO was successful against Gram-positive bacteria, and CuO had the best activity against Gram-negative bacteria.