Visible light-driven CdSe nanotube array photocatalyst
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NANO EXPRESS
Open Access
Visible light-driven CdSe nanotube array photocatalyst Haojun Zhu and Quan Li*
Abstract Large-scale CdSe nanotube arrays on indium tin oxide (ITO) glass have been synthesized using ZnO nanorod template. The strong visible light absorption in CdSe, its excellent photoresponse, and the large surface area associated with the tubular morphology lead to good visible light-driven photocatalytic capability of these nanotube arrays. Compared to freestanding nanoparticles, such one-piece nanotube arrays on ITO make it very convenient for catalyst recycling after their usage Keywords: Nanotube arrays, Template synthesis, II-VI semiconductors, Visible light photocatalysis
Background The development of nanometer-sized photocatalysts for efficient degradation of organic pollutants has attracted continuous research attention [1-4]. Among various morphologies of nanostructures, well-aligned pseudoone-dimensional (1D) nanostructures such as nanowire (NW) or nanotube (NT) arrays are of particular interest, since the specific morphology brings in several advantages: Its large surface-to-volume ratio prompts the surface-related chemical reactions, which is critical in most of the catalytic processes; when organized into arrays, the ordered NW/NT provides a direct pathway for charge carrier transfer to the conductive substrate. In addition, the NW/NT arrays may enhance light absorption by reducing the reflection or extending the optical path in the nanostructures [5,6]. The most extensively studied NW/NT array photocatalyst for photodegradation of organic pollutants is the titanium dioxide (TiO2) nanotube arrays, as it is environmentally benign, capable of total mineralization of organic contaminants, easy to fabricate, and cheap. Nevertheless, its large bandgap (3.2 eV for anatase and 3.0 eV for rutile) only allows the absorption in UV range of the solar spectrum. Although doping TiO2 with elements, such as V, Cr, Mn, Fe, C, N, S, F, etc., could extend the absorption spectrum of TiO2 to the visible region, other problems occur and lead to the decrease in the quantum efficiency [7,8]. * Correspondence: [email protected] Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong
Alternatively, direct employment of the narrower bandgap materials as the photocatalyst has been proposed as a possible solution. A few semiconductors have been investigated, such as II-VI materials (e.g., CdS [2,9] and CdSe [10,11]) and transition metal oxides (e.g., WO3 [12-14], Fe2O3 [15-18], Cu2O [19], Bi2WO6 [20,21], and ZnFe2O4 [22]). Nevertheless, most of the photocatalysts developed are the nanoparticles, which would not enjoy the advantage of the 1D morphology. In addition, after the nanoparticles are dispersed in the waste water for the catalytic reactions, it is troublesome to collect them after use. In the present work, well-aligned CdSe nanotube arrays on indium tin oxide (ITO)/glass are obtained by electrodepositing CdSe on the surface of ZnO nanorod followed by ZnO etching. Su
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