Copper sulfide nanotubes: facile, large-scale synthesis, and application in photodegradation
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- Wang, X., Fang, Z. & Lin, X. J Nanopart Res (2009) 11: 731. doi:10.1007/s11051-008-9480-2
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Large-scale synthesis of copper sulfide (CuS) nanotubes with uniform size could be achieved via a facile hydrothermal method. The whole process could be adjusted to prepare CuS with different nanostructures by simply changing the concentration of NaOH or reaction temperature while keeping other conditions unchanged. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Photoluminescence (PL) spectroscopy were used to characterize the products. The as-prepared CuS nanotubes showed good photocatalytic activity of degrading eosin Y under UV-vis light irradiation, which indicated the potential application of the CuS nanotubes in eliminating pollution and environmental protection.
Soon after the discovery of carbon nanotubes (Iijima 1991), inorganic nanotubes attracted considerable attention due to their novel electrical, optical, magnetic, and catalytic (Peralta-Inga et al. 2003; Kempa et al. 2003; Shen et al. 2006) properties and their potential applications in numerous areas. Various tube-like inorganic nanomaterials were fabricated, including metal oxides (Yan and Xue 2008; Dobley et al. 2001; Zhan et al. 2004; Muhr et al. 2000), metal sulfides (Hu et al. 2004; Yin et al. 2005; Zhou et al. 2007), metals (Cao et al. 2003; Sun and Xia 2004; Sander and Gao 2005; Yu et al. 2005), other metal salts (Souza Filho et al. 2004; Liang et al. 2004; Park et al. 2004), nonmetals (Journet et al. 1997; Schlittler et al. 2001), hydroxides (Fang et al. 2003; Zang et al. 2003), and heterostructures (Gu et al. 2007; Zhou et al. 2007a, b).
As an important semiconductor with unusual electrical, optical, and catalytic prosperities (Crespo et al. 2007), CuS was a promising material with potential applications in many fields such as cathode material, nanocrystallites, semiconductor, solar cells, light-emitting diodes, and biological labeling (Dobson et al. 2001). Many methods of synthesis of copper sulfide nanotubes had been explored, such as templating method (Wu et al. 2006; Yao et al. 2007; Zhang et al. 2007; Zhu et al. 2007), aqueous phase reaction (Ni et al. 2004), hydrogel synthesis (Kalyanikutty et al. 2006; Tan et al. 2005), and hydrothermal process (Lu et al. 2002). However, facile and large scale synthesis of CuS nanotubes was scarcely reported as far as we know. In this article, a facile hydrothermal route to synthesize copper sulfide nanotubes in large scale without any structure-directing surfactants was described. The shape of CuS nanotubes was controlled by adjusting the concentration of NaOH and the reaction temperature.
All reagents (analytical-grade purity) used in this work were gained from commercial market, and were used without any further purification. In a typical experimental procedure, 2.4 mmol CuCl2·2H2O and 2.4 mmol CH3CSNH2 (TAA) were dissolved in 20 mL distilled water, respectively, and sonicated for 5 min to give a clear solution. The two solutions were mixed and stirred vigorously for 5 min. A total of 10 mL of 0.4 M NaOH aqueous solution was added to the above mixture and stirred for 5 min at room temperature to yield an opaque (final concentration of NaOH is 0.08 M). The opaque was transferred into a Teflon-lined stainless steel autoclave with a capacity of 60 mL. The autoclave was heated to 160 °C and maintained at this temperature for 6 h. After the autoclave was cooled to room temperature, the flocculent black green precipitate was collected, and then washed with absolute ethanol and distilled water several times to remove any possible residual impurities. The as-obtained samples were dried in a vacuum-drying oven at 60 °C for 6 h before further characterization.
The X-ray powder diffraction patterns (XRD) of the samples were measured using a Shimadzu X-ray diffractometer (XRD-6000). The morphology, structure, and size of the samples were characterized by scanning electron microscopy (SEM, Hitachi, and Model S-4800) and transmission electron microscopy (TEM, Hitachi, Model H-800). The excitation and photoluminescence (PL) spectrum of the as-obtained samples was measured on an Edinburgh 920 fluorescence spectrophotometer with a Xe lamp at room temperature. The photocatalytic performance of CuS nanotubes was evaluated by the degradation of eosin Y under UV irradiation; an aqueous suspension of CuS was prepared by adding 100 mg CuS nanotubes to an aqueous solution of eosin Y (100 mL, 10−4 M). The solution was protected from light and stirred for 6 h to reach adsorption equilibrium and uniform dispersion before irradiation. Then, the solution was irradiated by UV lamp with wavelengths centered at 365 nm, which was placed 10 cm high over the solution for 60 min. At 10 min intervals after irradiation, the dispersion was centrifuged, and the eosin Y concentration was determined by using a UV–vis absorption spectroscopy (Shimadzu, Model UV-3010).
Results and discussions
In conclusion, uniform and well-defined CuS nanotubes in pure hexagonal phase was easily synthesized via a facile hydrothermal method and the product was obtained in high-yield. Experiments revealed that a successful morphological transformation of copper sulfide nanomaterials can be achieved at different concentrations of NaOH or various reaction temperatures. The PL and photodegradation results indicated that CuS nanotubes have an outstanding optical property.
Financial supports from the National Natural Science Foundation of China (20701002), the Special Project Grants of Anhui Normal University (2007xzx12), Science and Technological Fund of Anhui Province for Outstanding Youth (08040106834), and the Education Department of Anhui Province (No. 2006KJ006TD) are gratefully acknowledged.