0022-4766/18/5903-0739 © 2018 by Pleiades Publishing, Ltd. 739 Journal of Structural Chemistry. Vol. 59, No. 3, pp. 739-743, 2018. Original Russian Text © 2018 A. Anaraki Firooz, R. Abdullah Mirzaie, F. Kamrani. EFFECT OF MORPHOLOGICAL ZnO NANOSTRUCTURES ON THE OPTICAL AND DECOLORIZATION PROPERTIES A. Anaraki Firooz, R. Abdullah Mirzaie, and F. Kamrani 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 nanorod- like 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. DOI: 10.1134/S002247661803037X Keywords: ZnO, photodecolorization, morphology, optical, solid state reaction. INTRODUCTION In recent years, heterogeneous metal oxide semiconductor materials have been developed due to their photocatalytic ability in the degradation of various environmental pollutants under UV-light irradiation [1]. Optically, ZnO with a wide band gap (3.37 eV) and large binding energy at room temperature is suitable for short wavelength optoelectronic applications [2]. Both size and morphology have an important influence on the optical properties [3]. Therefore, the development of new types of the ZnO nanostructured photocatalyst with efficient electron/hole utilization, high surface areas, favorable recycling characteristics, and simple preparation is very important for practical applications [4]. It is rationally expected that some types of ZnO morphologies would be promising candidates for these applications [5]. In order to gain better performances of ZnO with regular nanostructures, various processing routes, including precipitation, pyrolysis, and hydrothermal methods, have been proposed to prepare nano- or microscaled ZnO particles with various sizes and morphologies [6-9]. Among all these methods, the solid state reaction method may be the most simple and effective way to prepare sufficiently crystallized materials at relatively low temperatures [10, 11]. Therefore, the development of a morphologically controllable synthesis of ZnO nanoparticles is urgently important to answer the demand for exploring the potentials of ZnO. Department of Chemistry, Faculty of Science, Shahid Rajaee Teacher Training University, Tehran, Iran; a.anaraki@srttu.edu. The text was submitted by the authors in English. Zhurnal Strukturnoi Khimii, Vol. 59, No. 3, pp. 761- 765, March-April, 2018. Original article submitted May 6, 2016; revised July 15, 2016.