Synthesis of Co and Cu codoped ZnO nanoparticles by citrate gel combustion method: Photocatalytic and antimicrobial activity

ZnO, single-doped (Co-ZnO, Cu-ZnO), and co-doped ZnO ((Co, Cu)/ZnO) were effectively synthesized by the citrate gel combustion technique. The samples were characterized by UV-visible diffuse reflectance spectroscopy (UV-vis-DRS), Fourier transforms infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and photoluminescence spectroscopy (PL). The average particle size was 30.33 nm as calculated from XRD patterns for (Co, Cu)/ZnO. UV-Vis absorption spectrum indicates that the co-doped ZnO exhibits increased visible light absorption compared to the undoped one.  The photoluminescence spectroscopy shows that the separation efficiency of photo-induced electrons and hole is enhanced by the co-doping strategy. (Co, Cu)/ZnO nanoparticles demonstrated a strong visible light response and high photocatalytic activity for Rhodamine B (RhB) degradation under irradiation by visible light (400-500 nm). The visible-light photocatalytic activity of the prepared  (Co, Cu)/ZnO may come about because of the incorporation of Co, Cu atoms in ZnO, photo-induced electron-hole pairs and extended the spectral response to the visible region. The antibacterial and antifungal activities of ZnO, Co-ZnO, Cu-ZnO, and (Co, Cu)/ZnO were studied respectively with Staphylococcus aureus (Gram-positive), Escherichia coli (Gram-negative) ( bacterial strain) and  Aspergillus flavus, Candida albicans (fungal strain). The (Co, Cu)/ZnO enhanced the antimicrobial activity.