Effect of Morphological ZnO Nanostructures on the Optical and Decolorization Properties

Abstract

ZnO photocatalysts with various morphologies (nanorod-like, nanosheet-like, and a mixture of rods and particles) are successfully prepared via simple solid states reactions at room temperature and 300 °C. The samples are characterized and used for photodecolorization of Congo red. It is found that there is a close relationship between photodecolorization, morphology, and size. The optical band gap value of nanorodlike ZnO is calculated to be about 4.0 eV. This value exhibits a nearly 0.7-0.9 eV blue shift from that of nanosheet-like ZnO and a mixture of ZnO rods and particles, which is related to a decrease in the size of particles and the achievement of the quantum confinement limit of nanoparticles. Also, nanorod-like ZnO shows higher decolorization in visible light as compared with other photocatalysts. It may be attributed to the special morphology (nanorod-like) with a smaller crystallite size. Nanorod-like ZnO could be considered as a promising photocatalyst for dye treatment.