Influence of cobalt doping concentration on ZnO/MWCNTs hybrid prepared by sol-gel method for antibacterial activity

In recent years, cobalt attracted large interest in biological application, due to its biocompatibility and low toxicity. The synthesis of Co doped-ZnO/MWCNTs hybrid by a wet chemical process been reported. The results confirmed prevailing that it is the size of Zinc Oxide NPs by determines the concentration of precursor. The effect of changing the concentration of Co doping on the physical properties of the prepared samples was investigated. The X-ray diffraction showed the formation of hexagonal wurtzite structure of zinc oxide with disappearance the diffraction peaks from cobalt. The crystalline size average increased from 25.66 to 33.33 nm with increasing concentration of cobalt. FESEM images confirmed the success of the growth of spherical clusters over the surface of interlocking cylindrical tubes and their association with a crimped surface. This indicates a formation Co doped-ZnO\MWCNT hybrid. In contrast, the UV–Vis spectra revealed that all hybrid nanostructures have high absorbance as well as the band gap narrowing with increasing cobalt-doping concentration, the band gap values of Co doped-ZnO/MWCNTs hybrid with Co (2%, 4%, 6%, 8%) are 3.29, 3.04, 2.99, and 2.97 eV, respectively. Moreover, the antibacterial effect reveals that, the synthesized Co doped-ZnO/MWCNTs hybrid has high activity toward the Gram-positive and Gram-negative bacteria High inhibition efficiency shown about (17.8–22) mm for E. coli and (19.5–20.5) mm for S. aureus at high concentration of Co dopant. Highlights Prepared ZnO/MWCNTs as hybrid and Co doped-ZnO/MWCNTs hybrid by simple sol–gel method and study the effect of variation transition metals like Co on the hybrid (ZnO/MWCNTs) for the antibacterial activity of the against the E. coli and S. aureus bacteria. To our knowledge, there is no report of Co/ZnO–MWCNTs prepared by sol–gel. Diethyl glycol a solvent was used in synthesizes of Co-doped ZnO/MWCNTs hybrid as the stabilizing factor, whose trap particle growth and quell particle conglomerate and gathering. the incorporation of Co +2 in ZnO lattice leads to the shift in the optical absorption and band gap narrowing (BGN) of ZnO reduced with increasing cobalt-doping concentration. The antibacterial activity of Co doped-ZnO–MWCNTs hybrid showed that increasing the concentration of the Co-dopant result in increasing the reactive oxygen spaces (ROS) and affected on their antibacterial activities.