Shape selective flower-like ZnO nanostructures prepared via structure-directing reagent free methods for efficient photocatalytic performance

Abstract

Zinc oxides (ZnO) nanoflowers have gained enormous attention in photocatalytic applications, despite of the fact that optimization of explicitly designed nanoflower for effective application is still underexplored. In this work, a variety of ZnO nanoflowers were successfully synthesized without using structure directing reagents. ZnO nanoflowers with different morphologies (viz., sea urchin, southern cone marigold and rose flowers) were synthesized through controlling the growth direction by concentrating on synthesis process alone. The photocatalytic performance of ZnO nanoflowers follow order of sea urchin > rose > southern cone marigold flower. These results suggest that optimal ZnO nanoflower (sea urchin) with improved physicochemical parameters such as specific surface area; reduced charge carrier recombination; high aspect ratio and uniform growth along c-axis etc. holds the significant advantage over other morphology. The effective separation and transportation of photogenerated charge carriers were boosted by the existence of high aspect ratio flower like structure, which is confirmed through the detailed photoelectrochemical study. The photocatalysis results substantiated that ZnO nanoflowers display the performance in a morphology-dependent manner and confirms that difference in the intrinsic morphology and the physical accessibility act as a deciding factor in optimizing the best performing ZnO nanoflower. Subsequently, a probable mechanism of optimal flower formation is also discussed.