Synergistic effect of ZnO nanoparticles with Cu2+ doping on antibacterial and photocatalytic activity

Abstract

The nanoparticles (NPs) of ZnO and Cu-doped ZnO samples were prepared using a chemical precipitation method specifically aimed at enhancing photocatalytic and antibacterial activity. The structural, morphological, phase constitutional, functional, elemental, and optical properties have been studied using Powder X-ray Diffraction (PXRD), Transmission Electron Microscopy (TEM), Ultra Violet diffused reflectance spectroscopy (UV-DRS), Fourier-transform infrared (FTIR) spectroscopy, and Thermogravimetric analysis (TGA). The crystallite size was calculated by using Debye Scherrer formula and the obtained average crystallite size of pure ZnO, ZnO-Cu2.5%, ZnO-Cu5%, and ZnO-Cu10% sample is 24.31 ± 0.12 nm, 25.72 ± 0.47 nm, 26.83 ± 0.39 nm, and 26.94 ± 0.29 nm, respectively. High-resolution Transmission Electron Microscope (HR-TEM) was used to calculate the d-spacing. The values of d-spacing for ZnO, ZnO-Cu2.5%, ZnO-Cu5%, and ZnO-Cu10% samples were measured as 0.248 nm, 0.266 nm, and 0.273 nm, respectively and corresponds to (101), (002) and (100) planes of ZnO, respectively which are well associated with the PXRD data (JCPDS card no. 36–1451). It was found that the doping concentration affects the crystallinity of the ZnO nanoparticles. The average grain size of ZnO, ZnO-Cu2.5%, ZnO-Cu5%, and ZnO-Cu10% is 35.75 ± 1.91 nm, 38.55 ± 2.31 nm, 45.39 ± 1.78 nm, and 50.65 ± 2.23 nm, respectively as determined from TEM images by using the ImageJ software. Further, photo-catalytic dye degradation was studied to understand the photocatalytic behavior of synthesized nanoparticles. The UV–Vis adsorption study has revealed that optimum doping of Cu is mandatory to get the highest degradation of methylene blue (MB) dye. It was observed that 5% Cu-doped ZnO NPs have the optimum photocatalytic activity. Furthermore, the antibacterial activity of various formulations on the gram-negative, facultative anaerobic, coliform bacterium Escherichia coli (E. coli) was studied to establish zone of inhibition (ZOI) values for ZnO and Cu-doped ZnO NPs. The current research indicated that 5% Cu-doped ZnO NPs have shown maximum inhibition and may be used for various antibacterial applications.