Investigation of ZnO nanocomposites with 2-D derivatives of graphene for photocatalytic and antibacterial activities

Zinc oxide (ZnO) nanoparticles (NPs) integrated with two-dimensional carbon allotropes, such as graphene oxide (GO) and reduced graphene oxide (rGO), exhibit significant potential as photocatalysts for the degradation of pollutants and antibacterial applications. In this study, ZnO NPs and ZnO nanocomposites with GO and rGO were synthesized via a simple, cost effective wet chemical technique. GO and rGO were prepared using the improved Hummer's method and chemical reduction, respectively. Structural analyses were performed using X-ray diffraction (XRD) and Raman spectroscopy. XRD analysis revealed hexagonal wurtzite-phase of ZnO NPs with an increase in the crystallite size upon the formation of composites with GO and rGO. Raman spectroscopy provided additional structural information. Scanning electron microscopy (SEM) study showed spherical shaped ZnO NPs decorating the wrinkled surfaces of GO and rGO sheets. Optical studies using UV–Visible and photoluminescence spectroscopy showed a reduced band gap and suppressed charge-carrier recombination in the nanocomposites compared with pristine ZnO. Photocatalytic evaluation using methylene blue as a pollutant demonstrated improved degradation efficiencies of 82% and 86%, for GO/ZnO and rGO/ZnO nanocomposites respectively, relative to 79% for pristine ZnO NPs within 90 min of solar light irradiation. Compared with the reported literature, the synthesized rGO/ZnO nanocomposites demonstrate comparable performance, offering the advantages of a simpler synthesis method, high degradation efficiency, shorter degradation time, and lower catalyst loading. Furthermore, antibacterial activity assays, including minimum inhibitory concentration, minimum bactericidal concentration, and zone of inhibition analyses, demonstrated enhanced antibacterial efficacy of rGO/ZnO NCs against E. coli and B. subtilis, highlighting their potential as effective antibacterial materials.