Structural and photocatalytic properties of nickel-doped zinc oxide powders with variable dopant contents Xiaoyan Cai a , Yun Cai a , Yongjun Liu b , He Li a , Fei Zhang a , Yude Wang a,n a Department of Materials Science and Engineering, Yunnan University, 650091 Kunming, People's Republic of China b Advanced Analysis and Measurement Center, Yunnan University, 650091 Kunming, People's Republic of China article info Article history: Received 13 November 2012 Received in revised form 3 March 2013 Accepted 20 March 2013 Keywords: A. Semiconductors B. Chemical synthesis C. Photoelectron spectroscopy D. Optical properties abstract The one-dimensional (1D) Ni-doped ZnO powders with variable dopant contents were synthesized at a low temperature (90 1C) using ZnCl 2 , NiCl 2 and NaOH solution as reaction precursors by a simple water bath method. The morphology and the microstructure of the as-prepared undoped and Ni-doped ZnO samples have been characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectra, X-ray Photoelectron Spectroscopy (XPS), and UV–vis spectroscopy. The results revealed that the samples were one-dimensional nanorods. Ni- doped ZnO nanorods were crystalline hexagonal wurtzite ZnO crystal structure, and the Ni ion was in a 2 + charge state in the crystal lattice of ZnO. The absorption spectra presented the existence of special two- absorption-region (strong UV-light and weak visible-light at 550–800 nm). The performance of Ni-doped ZnO powders as efficient photocatalyst was further demonstrated in the degradation of Rhodamine B (RB) under UV-light irradiation. The Ni-doped ZnO powders show high photocatalytic activity during the degradation of RB under UV-light. It was found that an appropriate amount of Ni dopant can greatly increase photocatalytic activity and the sample with 10% Ni doping exhibits the highest photocatalytic efficiency. & 2013 Elsevier Ltd. All rights reserved. 1. Introduction As an important II–VI semiconductor, ZnO is a promising material for the fabrication of high-technology applications such as light-emitting diodes, sensors, photoluminescent and photo- catalysts materials due to its wide band gap (3.37 eV), large exciton binding energy (60 mV), and excellent electro and optical properties [1–3]. Nanostructured ZnO has great research and application prospects for photocatalytic degradation of pollutants, on the one hand, the surface area of nano-ZnO increases rapidly and the reaction rate of nano-ZnO particle is 100–1000 times higher than normal ZnO as a result of relatively small particle size, on the other hand, nanostructured ZnO particle almost does not cause light scattering compared with the ordinary. In addition, ZnO nanomaterials which is known as the “environment-friendly material” also have the advantages of non-toxic, low cost and chemical stability, becoming the most promising and the most widely studied photocatalytic material after following TiO 2 [4]. Recently, one-dimensional (1D) ZnO nanomaterials, such as nano- wires, nanorods, nanobelts and nanotubes, have been extensively studied because not only they have larger surface area than microscale powders, which enlarges their contact surface during the reactions, but also their higher length-width ratio makes them easily to be filtered out after the reactions [5]. Up to now, one- dimensional ZnO nanostructures have been prepared by various routes, including thermal evaporation [6], metal organic chemical vapor deposition (MOCVD) [7], template method [8], hydrother- mal method [9], aqueous chemical growth (ACG) [10], etc. Among them, water bath method, as a branch of aqueous chemical growth, has great advantages in synthesizing one-dimensional nano-ZnO through easy operating, simple equipment and not harsh growing conditions, which makes the method more suitable and economic for large-scale production. The quick recombination of charge carriers is the main factor influencing the photocatalytic activity of ZnO. In order to improve the photocatalytic activity, different kinds of ions were doped into ZnO by different methods to inhibit the recombination of photo- induced electrons and holes [11–13]. Fu et al. [14] prepared the (Fe, Ni)-codoped ZnO nanosheets photocatalyst via a solution method, and discussed the effects of initial concentration of methyl orange, photocatalyst amount and initial pH of methyl orange solution on the photocatalytic efficiency of the nanosheets. Zhao et al. [5] newly reported that the Ni-doped ZnO nanorods with different concentration fabricated through hydrothermal method exhibited better photocatalytic activity than ZnO in the degradation of rhodamine B (RB). However, to our knowledge, the Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/jpcs Journal of Physics and Chemistry of Solids 0022-3697/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jpcs.2013.03.016 n Corresponding author. Tel: +86 871 6998372. E-mail address: ydwang@ynu.edu.cn (Y. Wang). Please cite this article as: X. Cai, et al., J. Phys. Chem. Solids (2013), http://dx.doi.org/10.1016/j.jpcs.2013.03.016i Journal of Physics and Chemistry of Solids ∎ (∎∎∎∎) ∎∎∎–∎∎∎