Novel sonochemical assisted hydrothermal approach towards the controllable synthesis of ZnO nanorods, nanocups and nanoneedles and their photocatalytic study

Abstract

ZnO nanovariants possessing different morphologies have been synthesized via a sonochemical as well as a sonochemical assisted hydrothermal (SAH) method. The synthesis process variables such as concentration of the precursors, ultrasonic irradiation period and duty cycle are observed to influence the resultant morphology of the ZnO nanostructures. Novel and significant morphologies of the ZnO nanostructures such as nanoneedles, tetrapods, nanowires, nanopetals, self assembled hexagonal rods and nanocups have been successfully obtained by controlling the process parameters. The surface morphology of the ZnO nanostructures was investigated using a scanning electron microscope (SEM). The SEM investigations showed that the nanoneedles originate from the hexagonal tube. Transmission electron microscope (TEM) analysis clearly demonstrates the nanocrystalline nature of the ZnO structures with unique morphologies like hexagonal nanocups. The ZnO nanostructures were characterized by UV-visible and photoluminescence spectrometers and a possible growth mechanism of the ZnO nanostructures is proposed. The photocatalytic activity of these nanostructures has also been presented. The ZnO nanostructures like nanocups and nanoneedles exhibit an excellent photocatalytic activity. Being a wide band gap semiconductor, these unique nanostructures will have a prospective application in ZnO based dye sensitized solar cells.