Doping iodine in CdS for pure hexagonal phase, narrower band gap, and enhanced photocatalytic activity
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Zhi Zhenga) Institute of Surface Micro and Nano Materials, Xuchang University, Xuchang 461000, People’s Republic of China
Lizhi Zhangb) Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, People’s Republic of China (Received 12 June 2010; accepted 21 December 2010)
Iodine-doped CdS (I-CdS) with controllable morphologies, pure hexagonal phase, and enhanced photocatalytic activity was synthesized via a mild hydrothermal process with polyvinylpyrrolidoneiodine (PVP-I) acting as the template-directing reagent and iodine source. The morphologies of the as-prepared samples could be adjusted from irregular cone-shaped particles to uneven microspheres, further to smooth microspheres, while the crystal phases were also transformed from mixed cubic and hexagonal phases to pure hexagonal phase upon increasing the molar ratio of PVP-I to Cd2+ from 0 to 2. The iodine doping could result in red shift of the absorption edges and band gap narrowing of the I-CdS samples. Importantly, a critical point of 0.5 of molar ratio of PVP-I to Cd2+ for iodine doping was found to be necessary for obtaining a pure hexagonal phase that facilitates the improving of photocatalytic activity on the degradation of Rhodamine B in aqueous solution under visible light irradiation. I. INTRODUCTION
In the past few decades, nanostructured materials have become a focus of scientific research, and considerable interests have been paid in the synthesis of semiconductor materials because of their specific electronic and optoelectronic properties. The nanostructured semiconductors usually show improved physical and chemical properties for their widespread potential applications, such as solar energy conversion devices and solar cells,1,2 light-emitting diodes,3,4 electronic and optoelectronic devices,5 and so on. As one of the most important applications, heterogeneous photocatalysis of semiconductors has been widely used for the removal of toxic organic and inorganic contaminates from water.6 However, although some metal oxide semiconductors, such as TiO2 and ZnO, can be used as photocatalysts, they have an inborn demerit of an ultraviolet (UV)-absorbing wide band gap and require chemical modification such as anionic7 or cationic8 doping to make use of visible light. To overcome these UV-absorbing shortcomings, some metal chalcogenides with narrow band gaps have been developed to efficiently overcome the shortcomings of
Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2011.3 710
J. Mater. Res., Vol. 26, No. 5, Mar 14, 2011
http://journals.cambridge.org
Downloaded: 19 Mar 2015
those wide-band-gap metal oxide materials. Among them, CdS, as one of the most vital and classical II–VI group semiconductors, has been extensively explored because its optimum band gap (2.3 eV) corresponds well with the spectrum of visible light as well as other thermodynamic and electrochemical properties suita
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