Hydrothermal synthesis of highly stable CuO nanostructures for efficient photocatalytic degradation of organic dyes S. Sonia a , S. Poongodi a , P. Suresh Kumar b , D. Mangalaraj a,n , N. Ponpandian a , C. Viswanathan a a Department of Nanoscience and Technology, Bharathiar University, Coimbatore 641046, India b Thin Film and Nanomaterials Laboratory, Department of Physics, Bharathiar University, Coimbatore 641046, India article info Available online 22 November 2014 Keywords: CuO Nanoleaves Hydrothermal Optical properties Photocatalytic abstract Highly stable CuO nanoleaves were synthesized by a simple hydrothermal method using tri-sodium citrate as a structure directing agent. The surface shape of the CuO nanoleaves was controlled and optimized by adjusting the molar concentration of the citrate. The structural properties of the prepared nanoleaves were investigated using X-ray diffraction which confirmed the formation of monoclinic CuO with an average crystallite size of 13–17 nm. FESEM and TEM analysis techniques confirmed the leaf-like morphology of CuO with sizes ranging from 250–300 nm. Analysis of the SAED pattern showed the polycrystalline nature of CuO nanoleaves. The band gap energy E g was evaluated as ranging from 2.67 to 2.97 eV from the UV–visible spectrum. CuO nanoleaves exhibited excellent recyclable photocatalytic activity with degradation values of 89% and 96% for methylene blue (MB) and methylene violet (MV) dyes respectively under ultraviolet light illumination. Thus, the present work is significant in terms of the potential applications in waste water treatment. & 2014 Elsevier Ltd. All rights reserved. 1. Introduction Recently, metal oxide nanostructures have attracted great attention in the field of photocatalysis to degrade the organic compounds present in contaminated water. This heterogeneous photocatalysis route leads to the complete degradation of organic pollutants through their interaction with the photogenerated charge carriers and reactive oxygen species [1]. As a heterogeneous catalyst, tenorite (CuO) has been used for the conversion of hydro- carbons into carbon dioxide and water and also for catalytic oxidation of cyclohexane and oxidative degradation of methylene blue in waste water [2–4]. Apart from the widely used photocatalysts such as TiO 2 and ZnO [5–7], p-type semiconductor CuO has been employed as an effective photocatalyst due to its high photochemical stability [8–10]. Even though CuO has been publicized as a good photocatalyst in many reports [11,12], its photocatalytic properties for the degradation of pollutants are directly related to the synthesis route, particle size and shape. Hence, a study of the synthesis and applications of CuO is both theoretically and practically important. In recent years, efforts have been made to synthesize a variety of well-defined CuO nanostructures such as nano- flowers, hollow spheres, nanodendrites, and nanorods by various wet chemical methods [13–16]. Among them, the hydrothermal process has been considered as the most promising route for the controlled synthesis of CuO nanostructures due to its simplicity and other advantages Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/mssp Materials Science in Semiconductor Processing http://dx.doi.org/10.1016/j.mssp.2014.10.012 1369-8001/& 2014 Elsevier Ltd. All rights reserved. n Corresponding author. Tel.: þ91 422 2425458; fax: þ91 422 2422387. E-mail address: dmraj800@yahoo.com (D. Mangalaraj). Materials Science in Semiconductor Processing 30 (2015) 585–591