Antimicrobial activity of ZnO-CeO2 nanocomposites: Preparation, characterization, impact of Zn/Ce content

In this research, antimicrobial nanoparticles (NPs) of zinc oxide (ZnO) and cerium oxide (CeO2) as well as nanocomposites (NCs) of ZnO-CeO2 at molar ratios of 8:2, 5:5, and 2:8 were prepared using the hydrothermal method at 160 degrees C for 5 h. The structural, morphological characteristics and antibacterial activity of the prepared NPs and NCs were investigated. The XRD results indicated that ZnO and CeO2 NPs, as well as the ZnO-CeO2 (8:2, 5:5, and 2:8) nanocomposites, possess a polycrystalline structure, exhibiting hexagonal wurtzite and cubic phases, respectively. The preferred orientations were along the (111) and (101) planes for ZnO and CeO2, respectively. The size of the crystals and the lattice strain were calculated using the Scherrer and Williamson-Hall (W-H) methods, with the lowest value (9.78 nm) and the highest strain (13.39 x 10-3) observed in the ZnO-CeO2 (2:8) composite, influenced by the CeO2 content. The surface properties analysed by FESEM demonstrated that ZnO NPs exhibit a nanorod shape with varying diameters of approximately 70-80 nm and lengths of about 300-500 nm. CeO2 NPs display spherical agglomerated particles, with a particle size ranging from 30 to 70 nm. In contrast, the nanocomposite samples show a mixture of rod and spherical NPs, where CeO2 NPs surround ZnO nanorods. The antibacterial activity of the prepared nanoparticles was screened against two common bacterial strains, Escherichia coli and Staphylococcus aureus. The composite sample ZnO-CeO2 (2:8) exhibited the strongest antibacterial activity against Staphylococcus aureus, with an inhibition zone of 22 mm. This study merges microbiology and nanotechnology to facilitate advancements in the development of a new antibacterial agent targeting Staph. and E. coli. The analysis revealed that zinc oxide and cerium oxide nanocomposites significantly enhance antibacterial activity, and a significant zone of inhibition was generated by the effects of the nanocomposites against pathogenic bacteria.