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Undoped ZnO, ZnO:Ag and ZnO:Ag/RGO (reduced graphene oxide) nanopowders were synthesized using co-precipitation method. The photocatalytic, antibacterial, structural, surface morphological and optical properties of the synthesized nanopowders were studied. From the X-ray diffractometer profiles, it is found that all the samples exhibit hexagonal structure without any secondary phase. The photocatalytic and antibacterial studies show that ZnO:Ag/RGO nanopowders exhibit enhanced photocatalytic and antibacterial activities when compared with undoped ZnO and ZnO:Ag nanopowders. The variations observed in the intensities of the PL emission peaks are correlated with the enhanced photocatalytic and antibacterial efficiencies. [ABSTRACT FROM PUBLISHER]

The present work reports the green synthesis of Zinc Oxide Nanoparticles (ZnO NPs) using aqueous Tabernaemontana divaricata green leaf extract. ZnO NPs have been characterized by X-ray diffraction (XRD), Ultra Violet–Visible (UV–Vis) studies, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Fourier Transform–Infra Red (FT–IR) analysis. XRD pattern analysis confirms the presence of pure hexagonal wurtzite crystalline structure of ZnO. The TEM images reveal the formation of spherical shape ZnO NPs with the sizes ranging from 20 to 50 nm. The FT–IR analysis suggests that the obtained ZnO NPs have been stabilized through the interactions of steroids, terpenoids, flavonoids, phenyl propanoids, phenolic acids and enzymes present in the leaf extract. Mechanism for the formation of ZnO NPs using Tabernaemontana divaricata as bioactive compound is proposed. As prepared ZnO NPs reveals antibacterial activity against three bacterial strains, Salmonella paratyphi , Escherichia coli and Staphylococcus aureus. The ZnO NPs shows higher antibacterial activity against S. aureus and E. coli and lesser antibacterial activity against S. paratyphi compared to the standard pharmaceutical formulation. Photocatalytic activity of synthesized ZnO NPs was analyzed for methylene blue (MB) dye degradation with sunlight. Almost complete degradation of dye occurred in 90 min. This nano-ZnO, prepared by eco-friendly method will be much useful for dye removal and bacterial decontamination. [ABSTRACT FROM AUTHOR]