ZnO nanoflowers: novel biogenic synthesis and enhanced photocatalytic activity.

We demonstrate a novel, unprecedented and eco-friendly mode for the biosynthesis of zinc oxide (ZnO) nanoflowers at ambient room temperature using Bacillus licheniformis MTCC 9555 and assessed their photocatalytic activity. The photocatalytic degradation of methylene blue (MB) dye was analyzed under UV-irradiation. An enhanced photocatalytic activity of ZnO nanoflowers was obtained compared to the earlier reports on ZnO nanostructures and other photocatalytic materials. The mechanism behind the enhanced photocatalytic activity was illustrated with diagrammatic representation. It is assumed that due to larger content of oxygen vacancy ZnO nanoflowers shows enhanced photocatalytic activity. Photostability of ZnO nanoflowers was analyzed for consecutive 3 cycles. The size and morphology of ZnO nanoflowers have been characterized by SEM, TEM and found to be in the size range of 250 nm to 1 μm with flower like morphology. It was found that ZnO nanoflowers was formed by agglomeration of ZnO nanorods. Further the EDX established the presence of the elemental signal of the Zn and O. XRD spectrum of ZnO nanoflowers confirmed 2θ values analogous to the ZnO nanocrystal. FTIR analysis was carried to determine the probable biomolecules responsible for stabilization of ZnO nanoflowers. The plausible mechanism behind the synthesis of ZnO nanoflowers by Bacillus licheniformis MTCC 9555 was also discussed with diagram representation.