2016. 57, 1 UDC 541.65:535.42 ZnO AND MgO NANOPARTICLES: SYNTHESIS AND COMPARATIVE STUDY ON THEIR PROPERTIES A. Bagheri ghomi Department of Chemistry, Center Tehran Branch, Islamic Azad University, Tehran, Iran E-mail: azbagheri@gmail.com Received January, 8, 2015 We report the optical and structural properties of ZnO and MgO nanoparticles. <...> The samples are obtained by a simple method using a new template of hexamethylene tetramine. <...> The optical properties of the samples are studied by UV-visible spectroscopy. <...> Their crystal structure and morphology are studied by XRD and scanning electron microscopy. <...> The absorption spectra of MgO and ZnO show that the optical band gaps are 4.27 eV and 3.02 eV, respectively. <...> In this investigation the photocatalytic degradation of indigo carmine (IC) in water is studied. <...> The effects of some parameters such as pH, amount of catalyst, initial concentration of dye, are examined. <...> Among semiconducting catalysts, zinc oxide (ZnO) has been extensively studied due to its low cost, nontoxicity, outstanding stability, and high efficiency [ 4—7]. <...> Owing to their large surface area, nanosized ZnO particles can be effectively utilized to enhance photocatalytic activity [ 8—11]. <...> Every solid has its own characteristic energy band structure. <...> A variation in the band structure is responsible for the wide range of electrical characteristics observed in various materials. <...> In semiconductors and insulators, electrons are confined to a number of energy bands and forbidden from other regions. <...> The conductivity of intrinsic semiconductors is strongly dependent on the band gap. <...> Magnesium oxide (MgO) as a versatile oxide material with assorted properties such as a large band gap, excellent thermodynamic stability, low dielectric constant, and low refractive index, finds extensive applications in catalysis, ceramics, toxic waste remediation, antibacterial materials, and as an additive in refractory, paint and superconductor products [12—16 ]. <...> Among various methods of the chemical synthesis there are the sol-gel method [ 17 ], hydrothermal [ 18 ], chemical vapor deposition [ 19 ], pulsed laser deposition [ 20 ], and molecular beam epitaxy [ 21 ]. <...> Hence, in this work, we have synthesized ZnO and MgO nanostructures by a simple reflux method. <...> For the UV <...>