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Wet chemical synthesis of Bi2S3 nanorods for efficient photocatalysis
Materials Letters 105 (2013) 12–15
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Wet chemical synthesis of Bi2S3 nanorods for efficient photocatalysis Yongfeng Luo a,b,n, Hong Chen a,n, Xi Li a,b, Zhiqiang Gong a, Xinjun Wang a, Xiaofang Peng a, Mengdong He a, Zhongzhi Sheng a a b
Institute of Mathematics and Physics, Central South University of Forestry and Technology, Changsha, Hunan 410004, China State Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai 200433, China
art ic l e i nf o
a b s t r a c t
Article history: Received 1 February 2013 Accepted 2 April 2013 Available online 11 April 2013
Uniform Bi2S3 nanorods (NRs) growing along [001] have been synthesized for the first time by a “green” wet chemical route. A possible formation mechanism for the growth process of the Bi2S3 spheres has been proposed. The prepared catalyst is characterized by field-emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and X-ray diffraction. The catalyst shows high and stable photocatalytic activity for the degradation of persistent toxic organic pollutants under visible (4 420 nm) light irradiation. More importantly, this synthesis method can be economical for a scale-up process, and may also be applicable to the preparation of other metal sulfides semiconductors for catalysis and other applications. & 2013 Elsevier B.V. All rights reserved.
Keywords: Bi2S3 nanorods Wet chemical Photocatalysis Organic pollutants
1. Introduction One-dimensional (1D) semiconductors, such as nanotubes, nanowires, nanorods, and nanobelts, have attracted intensive interest due to their importance in fundamental research and potential wideranging applications [1–4]. Especially, much effort has been devoted to the controlled synthesis of 1D nanostructures from chalcogenides semiconductors due to their interesting physical properties and potential applications in optoelectric and thermoelectric nanoscale devices. Bismuth sulfide (Bi2S3), which belongs to the family of main group metal chalcogenides AV2 BVI 3 (A¼ As, Sb, and Bi; B¼S, Se, and Te), is an important class of semiconductors with numerous applications, including photovoltaics [5,6] and thermoelectrics [7,8]. To date, much attention has been paid to preparing Bi2S3 nano- and microstructured materials through various synthesis approaches, including direct element reaction at high temperature [9], chemical vapor deposition [10,11], solvothermal and hydrothermal methods [12–15], sonochemical method [16], microwave irradiation [17], solventless thermolysis [18], and ionic liquid method [19]. However, the methods mentioned above generally require rigorous experimental conditions, expensive reagents, or intricate instruments, making it difficult to scale up the production. Therefore, the development of cost-effective and environment friendly methods suitable for the large-scale synthesis of Bi2S3 nano- and microstructures is of great importance and a challenge for their industrial applications.
n
Corresponding authors at: Central South University of Forestry and Technology, Institute of Mathematics and Physics, 498 South Shaoshan Road, Changsha, Hunan 410004, China. Tel./fax: +86 731 85623353. E-mail addresses: [email protected] (Y. Luo), chenhongcs@126. com (H. Chen). 0167-577X/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.04.006
In addition, finding new ways of treating environmental pollution is a great challenge and a major area of scientific study. Up to now, most photocatalysts have been based on metal oxides such as TiO2 and ZnO. However, the low quantum efficiency and high bandgap of semiconductor oxides limit their photocatalytic activity under visible light. Bi2S3 is a typical lamellar structured semiconductor with a bulk direct bandgap ranging from 1.3 to 1.7 eV [20], which is a good light-harvesting semiconductor with absorption in the visible and near-IR part of the solar spectrum, allowing their applications in photocatalysis. However, the photocatalytic properties of Bi2S3 have been scarcely reported. Therefore, the photocatalytic activity of pure Bi2S3 is worth studying further from the viewpoints of both fundamental research and applications in environmental treatment. Herein, for the first time, we report a template-free “green” wet chemical route for the gram-scale synthesis of Bi2S3 nanorods (about 40 nm in diameter) composed of orthorhombic phase Bi2S3 crystallites. This wet chemical route has the following advantages: (i) the route is inexpensive and suitable for the gram-scale synthesis and has excellent yield ( 499%), which is potentially suitable for industrial production; (ii) no extra template or capping agent is required and (iii) the catalyst can work efficiently under visible light irradiation. More importantly, we believe that this route can be extended to the synthesis of other transition-metal sulfide photocatalysts.
2. Experimental Synthesis of Bi2S3 nanorods: All reagents used in the experiments were of analytical grade (purchased from Shanghai Chem. Co.), and used without further purification. In a typical synthesis,
Y. Luo et al. / Materials Letters 105 (2013) 12–15
1.44 g Bi(NO3)3 5H2O was dissolved in 200 ml methanol and 10 ml concentrated hydrochloric acid. After the Bi(NO3)3 5H2O dissolved completely, 0.3 g thiourea was added to the mixture solution. After stirring for 30 min, the clear solution was transferred to an autoclave, and then a pressure of 1 MPa nitrogen was imposed before initiating heating. The mixture solution was heated to 150 1C for 1 h, and then to 240 1C for 2 h. After the supercritical fluid drying (SCFD), the black Bi2S3 powder (1.02 g) was collected, and then washed with ultrapure water and ethanol several times. Characterization of Bi2S3 nanorods: The crystalline structure of the catalysts was characterized by powder X-ray diffraction (XRD) employing a scanning rate of 0.051/s in a 2θ range from 101 to 801, in a Bruker D8 Advance using monochromatized Cu Kα radiation. The morphology and particle size of catalysts were analyzed by transmission electron microscopy using a Tecnai G20 (FEI) TEM operated at an accelerating voltage of 200 kV. HRTEM and electron diffraction data are collected using an FEI Titan TEM operated at 300 kV. A Quanta 200 scanning electron microscope was used to investigate the overall morphology of the product. Photodegradation experiment: The photoactivity of the samples was tested by the degradation of RhB under visible light (4 420 nm) or near UV (365 nm) irradiation. In a typical experiment, 50 mg photocatalyst and 50 ml aqueous solution of RhB (1.0 10−5 mol/L) were added into a flask; then the mixed solution was oscillated in darkness for 24 h. After reaching adsorption equilibrium, the photocatalytic reaction was initiated by irradiating the system with a 350 W Xenon lamp. At given time intervals,
13
4 ml aliquots were collected, centrifuged, and then filtered to remove the catalyst particles for analysis. The filtrates were finally analyzed using a UV–vis spectrophotometer (UV-2450). For comparison, the photocatalytic activity of Degussa P25 was also tested at the same experimental conditions.
3. Results and discussion The morphologies of the products are demonstrated in the SEM and TEM images. As shown in Fig. 1a–d, the SEM and TEM images of Bi2S3 obtained at 200 1C for 2 h show that the sample consists of monodisperse nanorods with a diameter in the range 20–40 nm and length in the range 200–600 nm. Fig. 1e shows the XRD pattern of the as-prepared Bi2S3 nanorods; all of the peaks can be indexed as the orthorhombic phase (space group Pbnm) of Bi2S3 with cell constants of a ¼11.14 Å, b¼ 11.30 Å, and c ¼3.98 Å, which are consistent with the values in the standard card (JCPDS 170320). No peaks of any other impurities were detected, indicating the high purity of the product. The phase purity and chemical composition of the product were confirmed by EDX analysis (Fig. 1f), which clearly demonstrates that the Bi2S3 nanorod is composed of only Bi and S (the signal of Cu is from the copper grid) with a molar ratio of 1:1.53, which is close to that of the standard stoichiometric composition of the Bi2S3 phase. The amount of pure Bi2S3 nanorod product can be easily scaled up to several grams by simply scaling the amount of reactants.
Fig. 1. (a, b) FESEM images, (c, d) TEM images, (e) XRD pattern and (f) EDX analysis of the as-prepared 1D Bi2S3 nanorod.
14
Y. Luo et al. / Materials Letters 105 (2013) 12–15
To identify the detailed crystallographic structure and orientation of the Bi2S3 nanorod, high-resolution TEM (HRTEM) and selected area electron microdiffraction (SAED) were used to characterize the sample. Fig. 2a shows the HRTEM image of a single Bi2S3 nanorod oriented with its [120] zone axis perpendicular to the substrate, and as a result the {001} and {21̄0} reflections appear in the corresponding SAED pattern (Fig. 2b) parallel and perpendicular to the [002] direction (the long axis of the nanorod), respectively. The HRTEM images (Fig. 2c, d) reveal that the perpendicular interlayer spacing is about 0.199 nm, corresponding to the interlayer distance of (002) plane of the Pbnm Bi2S3 phase, which indicates the [001] growth direction of the nanorod. Herein, we propose a formation mechanism of Bi2S3 nanorods on the basis of the TEM observations. Initially, the isomerization of
thiourea may occur below 150 1C [Eq. (1)].
(1)
Then, the generated isothiourea can have a strong nucleophilic substitution of the Bi3+ cation in Bi(NO3)3 nitrate solution to form Bi2S3 nanocrystal precursors [Eq. (2)]. The formed precursors decompose into Bi2S3 crystallites when the temperature is increased to 200 1C. As the temperature increased to 240 1C, these
Fig. 2. (a, c) HRTEM images of single Bi2S3 nanorod with (b) SAED pattern obtained from the imaged area and (d) HRTEM image of region 1 marked with blue square in (c). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 3. (a) The absorption spectrum of a solution of RhB (1. 10−5 M, 50 ml) in the presence of Bi2S3 nanorod (50 mg) under visible light ( 4420 nm) irradiation and (b) the C/ C0 vs time curves of RhB photodegration under visible light ( 4420 nm) irradiation.
Y. Luo et al. / Materials Letters 105 (2013) 12–15
crystallites self-assembled into nanorods under supercritical conditions in order to decrease their surface energies [21,22]. It should be mentioned that in the synthesis, it is essential to maintain the temperature of the reaction solution at 150 1C for 1 h; otherwise the thiourea will decompose resulting in very low yield. To evaluate the photocatalytic capability of the Bi2S3 nanorods, we investigated its photocatalytic activity by photocatalytic degradation of RhB as a probe reaction. Fig. 3a shows the change of absorption spectra of an RhB aqueous solution (initial concentration is 1.0 10−5 M, 50 ml) in the presence of 50 mg Bi2S3 nanorods under exposure to visible light (4420 nm). The absorption peak at λ¼553 nm drops rapidly with extension of the exposure time and completely disappears after about 240 min. No new absorption bands appear in either the visible or ultraviolet region, which indicates the complete photodegradation of RhB. A further comparative experiment was performed as shown in Fig. 3b. Under similar experimental conditions, Bi2S3 nanorods photocatalyst showed much higher activity than that of commercial Degussa P25 under visible light ( 4420 nm) irradiation. 4. Conclusions In summary, orthorhombic Bi2S3 nanorod has been successfully synthesized for the first time using an efficient “green” wet chemical synthesis approach. A possible growth mechanism was proposed to explain the formation of the Bi2S3 nanorod selfassembled with crystallites. The Bi2S3 nanorods display very high photocatalytic activity and are even more efficient than that of the particularly successful photocatalyst Degussa P25 under visible light irradiation. Moreover, this synthesis method may be economical for a scale-up process, and provides guidance to design and fabrication of novel photoactive materials for catalysis and other applications.
15
Acknowledgments This work was supported by the National Natural Science Foundation of China (Nos. 11247030 and 11174372), Open Topics of State Key Laboratory of Molecular Engineering of Polymers (No. K2012-12), and Introducing High-level Talent Research Start Fund of Central South University of Forestry and Technology (No. 1040281).
References [1] Xia Y, Yang P, Sun Y, Wu Y, Mayers B, Gates B, et al. Adv Mater 2003;15:353–89. [2] Cheng B, Russell JM, Shi W, Zhang L, Samulski ET. J Am Chem Soc 2004;126:5972–3. [3] Pan Z, Dai Z, Wang Z. Science 2001;291:1947–9. [4] Towe KM. Science 2001;291:436–7. [5] Shaw M, Holmberg S, Kostylev S. Phys Rev Lett 1973;31:542–5. [6] Suarez R, Nair P, Kamat PV. Langmuir 1998;14:3236–41. [7] Telkes M. J Appl Phys 1947;18:1116–27. [8] Chen B, Uher C, Iordanidis L, Kanatzidis MG. Chem Mater 1997;9:1655–8. [9] Kaito C, Saito Y, Fujita K. J Cryst Growth 1989;94:967–77. [10] Ye C, Meng G, Jiang Z, Wang Y, Wang G, Zhang L. J Am Chem Soc 2002;124:15180–1. [11] Koh YW, Lai CS, Du AY, Tiekink ERT, Loh KP. Chem Mater 2003;15:4544–54. [12] Yu SH, Yang J, Wu YS, Han ZH, Xie Y, Qian YT. Mater Res Bull 1998;33:1661–6. [13] Yu SH, Shu L, Yang J, Han ZH, Qian YT, Zhang YH. J Mater Res 1999;14:4157–62. [14] Wang D, Shao M, Yu D, Li G, Qian Y. J Cryst Growth 2002;243:331–5. [15] Liu Z, Peng S, Xie Q, Hu Z, Yang Y, Zhang S, et al. Adv Mater 2003;15:936–40. [16] Wang H, Zhu JJ, Zhu JM, Chen HY. J Phys Chem B 2002;106:3848–54. [17] Liao XH, Wang H, Zhu JJ, Chen HY. Mater Res Bull 2001;36:2339–46. [18] Sigman Jr MB, Korgel BA. Chem Mater 2005;17:1655–60. [19] Jiang J, Yu SH, Yao WT, Ge H, Zhang GZ. Chem Mater 2005;17:6094–100. [20] Vogel R, Hoyer P, Weller H. J Phys Chem 1994;98:3183–8. [21] Liu Y, Hu J, Zhou T, Che R, Li J. J Mater Chem 2011;21:16621–7. [22] Liu Y, Hu J, Ngo C, Prikhodko S, Kodambaka S, Li J, et al. Appl Catal B 2011;106:212–9.
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Wet chemical synthesis of Bi2S3 nanorods for efficient photocatalysis Yongfeng Luo a,b,n, Hong Chen a,n, Xi Li a,b, Zhiqiang Gong a, Xinjun Wang a, Xiaofang Peng a, Mengdong He a, Zhongzhi Sheng a a b
Institute of Mathematics and Physics, Central South University of Forestry and Technology, Changsha, Hunan 410004, China State Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai 200433, China
art ic l e i nf o
a b s t r a c t
Article history: Received 1 February 2013 Accepted 2 April 2013 Available online 11 April 2013
Uniform Bi2S3 nanorods (NRs) growing along [001] have been synthesized for the first time by a “green” wet chemical route. A possible formation mechanism for the growth process of the Bi2S3 spheres has been proposed. The prepared catalyst is characterized by field-emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and X-ray diffraction. The catalyst shows high and stable photocatalytic activity for the degradation of persistent toxic organic pollutants under visible (4 420 nm) light irradiation. More importantly, this synthesis method can be economical for a scale-up process, and may also be applicable to the preparation of other metal sulfides semiconductors for catalysis and other applications. & 2013 Elsevier B.V. All rights reserved.
Keywords: Bi2S3 nanorods Wet chemical Photocatalysis Organic pollutants
1. Introduction One-dimensional (1D) semiconductors, such as nanotubes, nanowires, nanorods, and nanobelts, have attracted intensive interest due to their importance in fundamental research and potential wideranging applications [1–4]. Especially, much effort has been devoted to the controlled synthesis of 1D nanostructures from chalcogenides semiconductors due to their interesting physical properties and potential applications in optoelectric and thermoelectric nanoscale devices. Bismuth sulfide (Bi2S3), which belongs to the family of main group metal chalcogenides AV2 BVI 3 (A¼ As, Sb, and Bi; B¼S, Se, and Te), is an important class of semiconductors with numerous applications, including photovoltaics [5,6] and thermoelectrics [7,8]. To date, much attention has been paid to preparing Bi2S3 nano- and microstructured materials through various synthesis approaches, including direct element reaction at high temperature [9], chemical vapor deposition [10,11], solvothermal and hydrothermal methods [12–15], sonochemical method [16], microwave irradiation [17], solventless thermolysis [18], and ionic liquid method [19]. However, the methods mentioned above generally require rigorous experimental conditions, expensive reagents, or intricate instruments, making it difficult to scale up the production. Therefore, the development of cost-effective and environment friendly methods suitable for the large-scale synthesis of Bi2S3 nano- and microstructures is of great importance and a challenge for their industrial applications.
n
Corresponding authors at: Central South University of Forestry and Technology, Institute of Mathematics and Physics, 498 South Shaoshan Road, Changsha, Hunan 410004, China. Tel./fax: +86 731 85623353. E-mail addresses: [email protected] (Y. Luo), chenhongcs@126. com (H. Chen). 0167-577X/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.04.006
In addition, finding new ways of treating environmental pollution is a great challenge and a major area of scientific study. Up to now, most photocatalysts have been based on metal oxides such as TiO2 and ZnO. However, the low quantum efficiency and high bandgap of semiconductor oxides limit their photocatalytic activity under visible light. Bi2S3 is a typical lamellar structured semiconductor with a bulk direct bandgap ranging from 1.3 to 1.7 eV [20], which is a good light-harvesting semiconductor with absorption in the visible and near-IR part of the solar spectrum, allowing their applications in photocatalysis. However, the photocatalytic properties of Bi2S3 have been scarcely reported. Therefore, the photocatalytic activity of pure Bi2S3 is worth studying further from the viewpoints of both fundamental research and applications in environmental treatment. Herein, for the first time, we report a template-free “green” wet chemical route for the gram-scale synthesis of Bi2S3 nanorods (about 40 nm in diameter) composed of orthorhombic phase Bi2S3 crystallites. This wet chemical route has the following advantages: (i) the route is inexpensive and suitable for the gram-scale synthesis and has excellent yield ( 499%), which is potentially suitable for industrial production; (ii) no extra template or capping agent is required and (iii) the catalyst can work efficiently under visible light irradiation. More importantly, we believe that this route can be extended to the synthesis of other transition-metal sulfide photocatalysts.
2. Experimental Synthesis of Bi2S3 nanorods: All reagents used in the experiments were of analytical grade (purchased from Shanghai Chem. Co.), and used without further purification. In a typical synthesis,
Y. Luo et al. / Materials Letters 105 (2013) 12–15
1.44 g Bi(NO3)3 5H2O was dissolved in 200 ml methanol and 10 ml concentrated hydrochloric acid. After the Bi(NO3)3 5H2O dissolved completely, 0.3 g thiourea was added to the mixture solution. After stirring for 30 min, the clear solution was transferred to an autoclave, and then a pressure of 1 MPa nitrogen was imposed before initiating heating. The mixture solution was heated to 150 1C for 1 h, and then to 240 1C for 2 h. After the supercritical fluid drying (SCFD), the black Bi2S3 powder (1.02 g) was collected, and then washed with ultrapure water and ethanol several times. Characterization of Bi2S3 nanorods: The crystalline structure of the catalysts was characterized by powder X-ray diffraction (XRD) employing a scanning rate of 0.051/s in a 2θ range from 101 to 801, in a Bruker D8 Advance using monochromatized Cu Kα radiation. The morphology and particle size of catalysts were analyzed by transmission electron microscopy using a Tecnai G20 (FEI) TEM operated at an accelerating voltage of 200 kV. HRTEM and electron diffraction data are collected using an FEI Titan TEM operated at 300 kV. A Quanta 200 scanning electron microscope was used to investigate the overall morphology of the product. Photodegradation experiment: The photoactivity of the samples was tested by the degradation of RhB under visible light (4 420 nm) or near UV (365 nm) irradiation. In a typical experiment, 50 mg photocatalyst and 50 ml aqueous solution of RhB (1.0 10−5 mol/L) were added into a flask; then the mixed solution was oscillated in darkness for 24 h. After reaching adsorption equilibrium, the photocatalytic reaction was initiated by irradiating the system with a 350 W Xenon lamp. At given time intervals,
13
4 ml aliquots were collected, centrifuged, and then filtered to remove the catalyst particles for analysis. The filtrates were finally analyzed using a UV–vis spectrophotometer (UV-2450). For comparison, the photocatalytic activity of Degussa P25 was also tested at the same experimental conditions.
3. Results and discussion The morphologies of the products are demonstrated in the SEM and TEM images. As shown in Fig. 1a–d, the SEM and TEM images of Bi2S3 obtained at 200 1C for 2 h show that the sample consists of monodisperse nanorods with a diameter in the range 20–40 nm and length in the range 200–600 nm. Fig. 1e shows the XRD pattern of the as-prepared Bi2S3 nanorods; all of the peaks can be indexed as the orthorhombic phase (space group Pbnm) of Bi2S3 with cell constants of a ¼11.14 Å, b¼ 11.30 Å, and c ¼3.98 Å, which are consistent with the values in the standard card (JCPDS 170320). No peaks of any other impurities were detected, indicating the high purity of the product. The phase purity and chemical composition of the product were confirmed by EDX analysis (Fig. 1f), which clearly demonstrates that the Bi2S3 nanorod is composed of only Bi and S (the signal of Cu is from the copper grid) with a molar ratio of 1:1.53, which is close to that of the standard stoichiometric composition of the Bi2S3 phase. The amount of pure Bi2S3 nanorod product can be easily scaled up to several grams by simply scaling the amount of reactants.
Fig. 1. (a, b) FESEM images, (c, d) TEM images, (e) XRD pattern and (f) EDX analysis of the as-prepared 1D Bi2S3 nanorod.
14
Y. Luo et al. / Materials Letters 105 (2013) 12–15
To identify the detailed crystallographic structure and orientation of the Bi2S3 nanorod, high-resolution TEM (HRTEM) and selected area electron microdiffraction (SAED) were used to characterize the sample. Fig. 2a shows the HRTEM image of a single Bi2S3 nanorod oriented with its [120] zone axis perpendicular to the substrate, and as a result the {001} and {21̄0} reflections appear in the corresponding SAED pattern (Fig. 2b) parallel and perpendicular to the [002] direction (the long axis of the nanorod), respectively. The HRTEM images (Fig. 2c, d) reveal that the perpendicular interlayer spacing is about 0.199 nm, corresponding to the interlayer distance of (002) plane of the Pbnm Bi2S3 phase, which indicates the [001] growth direction of the nanorod. Herein, we propose a formation mechanism of Bi2S3 nanorods on the basis of the TEM observations. Initially, the isomerization of
thiourea may occur below 150 1C [Eq. (1)].
(1)
Then, the generated isothiourea can have a strong nucleophilic substitution of the Bi3+ cation in Bi(NO3)3 nitrate solution to form Bi2S3 nanocrystal precursors [Eq. (2)]. The formed precursors decompose into Bi2S3 crystallites when the temperature is increased to 200 1C. As the temperature increased to 240 1C, these
Fig. 2. (a, c) HRTEM images of single Bi2S3 nanorod with (b) SAED pattern obtained from the imaged area and (d) HRTEM image of region 1 marked with blue square in (c). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 3. (a) The absorption spectrum of a solution of RhB (1. 10−5 M, 50 ml) in the presence of Bi2S3 nanorod (50 mg) under visible light ( 4420 nm) irradiation and (b) the C/ C0 vs time curves of RhB photodegration under visible light ( 4420 nm) irradiation.
Y. Luo et al. / Materials Letters 105 (2013) 12–15
crystallites self-assembled into nanorods under supercritical conditions in order to decrease their surface energies [21,22]. It should be mentioned that in the synthesis, it is essential to maintain the temperature of the reaction solution at 150 1C for 1 h; otherwise the thiourea will decompose resulting in very low yield. To evaluate the photocatalytic capability of the Bi2S3 nanorods, we investigated its photocatalytic activity by photocatalytic degradation of RhB as a probe reaction. Fig. 3a shows the change of absorption spectra of an RhB aqueous solution (initial concentration is 1.0 10−5 M, 50 ml) in the presence of 50 mg Bi2S3 nanorods under exposure to visible light (4420 nm). The absorption peak at λ¼553 nm drops rapidly with extension of the exposure time and completely disappears after about 240 min. No new absorption bands appear in either the visible or ultraviolet region, which indicates the complete photodegradation of RhB. A further comparative experiment was performed as shown in Fig. 3b. Under similar experimental conditions, Bi2S3 nanorods photocatalyst showed much higher activity than that of commercial Degussa P25 under visible light ( 4420 nm) irradiation. 4. Conclusions In summary, orthorhombic Bi2S3 nanorod has been successfully synthesized for the first time using an efficient “green” wet chemical synthesis approach. A possible growth mechanism was proposed to explain the formation of the Bi2S3 nanorod selfassembled with crystallites. The Bi2S3 nanorods display very high photocatalytic activity and are even more efficient than that of the particularly successful photocatalyst Degussa P25 under visible light irradiation. Moreover, this synthesis method may be economical for a scale-up process, and provides guidance to design and fabrication of novel photoactive materials for catalysis and other applications.
15
Acknowledgments This work was supported by the National Natural Science Foundation of China (Nos. 11247030 and 11174372), Open Topics of State Key Laboratory of Molecular Engineering of Polymers (No. K2012-12), and Introducing High-level Talent Research Start Fund of Central South University of Forestry and Technology (No. 1040281).
References [1] Xia Y, Yang P, Sun Y, Wu Y, Mayers B, Gates B, et al. Adv Mater 2003;15:353–89. [2] Cheng B, Russell JM, Shi W, Zhang L, Samulski ET. J Am Chem Soc 2004;126:5972–3. [3] Pan Z, Dai Z, Wang Z. Science 2001;291:1947–9. [4] Towe KM. Science 2001;291:436–7. [5] Shaw M, Holmberg S, Kostylev S. Phys Rev Lett 1973;31:542–5. [6] Suarez R, Nair P, Kamat PV. Langmuir 1998;14:3236–41. [7] Telkes M. J Appl Phys 1947;18:1116–27. [8] Chen B, Uher C, Iordanidis L, Kanatzidis MG. Chem Mater 1997;9:1655–8. [9] Kaito C, Saito Y, Fujita K. J Cryst Growth 1989;94:967–77. [10] Ye C, Meng G, Jiang Z, Wang Y, Wang G, Zhang L. J Am Chem Soc 2002;124:15180–1. [11] Koh YW, Lai CS, Du AY, Tiekink ERT, Loh KP. Chem Mater 2003;15:4544–54. [12] Yu SH, Yang J, Wu YS, Han ZH, Xie Y, Qian YT. Mater Res Bull 1998;33:1661–6. [13] Yu SH, Shu L, Yang J, Han ZH, Qian YT, Zhang YH. J Mater Res 1999;14:4157–62. [14] Wang D, Shao M, Yu D, Li G, Qian Y. J Cryst Growth 2002;243:331–5. [15] Liu Z, Peng S, Xie Q, Hu Z, Yang Y, Zhang S, et al. Adv Mater 2003;15:936–40. [16] Wang H, Zhu JJ, Zhu JM, Chen HY. J Phys Chem B 2002;106:3848–54. [17] Liao XH, Wang H, Zhu JJ, Chen HY. Mater Res Bull 2001;36:2339–46. [18] Sigman Jr MB, Korgel BA. Chem Mater 2005;17:1655–60. [19] Jiang J, Yu SH, Yao WT, Ge H, Zhang GZ. Chem Mater 2005;17:6094–100. [20] Vogel R, Hoyer P, Weller H. J Phys Chem 1994;98:3183–8. [21] Liu Y, Hu J, Zhou T, Che R, Li J. J Mater Chem 2011;21:16621–7. [22] Liu Y, Hu J, Ngo C, Prikhodko S, Kodambaka S, Li J, et al. Appl Catal B 2011;106:212–9.