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Controlling morphologies of Bi2S3 nanostructures synthesized by glycolthermal method
Materials Letters 72 (2012) 104–106
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Controlling morphologies of Bi2S3 nanostructures synthesized by glycolthermal method Anukorn Phuruangrat a,⁎, Somchai Thongtem b, Titipun Thongtem c,⁎⁎ a b c
Department of Materials Science and Technology, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand
a r t i c l e
i n f o
Article history: Received 14 September 2011 Accepted 22 December 2011 Available online 29 December 2011 Keywords: Semiconductors X-ray techniques Electron microscopy
a b s t r a c t Single crystalline orthorhombic Bi2S3 nanostructures with different morphologies were synthesized by the 180 °C and 12 h glycolthermal reactions, using ethylene glycol, propylene glycol and polyethylene glycol with different molecular weights as solvents. The as-synthesized products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED). In the present research, different solvents played the role in the product morphologies. A formation mechanism of Bi2S3 nanostructures was also proposed. © 2011 Elsevier B.V. All rights reserved.
1. Introduction Generally, nanostructured materials exhibit novel properties, comparing to their bulks due to their quantum confinement effect and number of free electrons. Much effort has been dedicated to achieve in controlling over the morphologies [1–3]. Among them, ceria nanospindles as a catalyst for oxidation of CO were synthesized via a simple template-free solvothermal treatment [4], large-scale synthesis of single-crystalline and uniform CeO2 nanorods by a precipitation method [5], and CeO2 nanoplates, nanotubes, and nanorods by CTAB assisted hydrothermal synthesis, including the study of their morphologies on the oxidation of CO [6]. Over the past decades, chalcogenide semiconductors (A2X3, A = Sb, Bi, As, and X = S, Se, Te) have received considerable attention due to their wide applications in television cameras with photoconducting targets, thermoelectric devices, optoelectronic devices, and IR spectroscopy photovoltaic converters, including their unique thermal, mechanical, electron transport, phonon transport, optical and non-linear optical properties [2,3,7]. Particularly, Bi2S3 is a low direct band gap (1.3–1.7 eV) layered semiconductor that crystallizes in orthorhombic system with a promising candidate for a number of applications. It has large absorption coefficient, and is an ideal candidate for solar cells and photodetectors in the visible region, including thermoelectric applications [2,7–10].
⁎ Corresponding author. Tel.: + 66 74 288374; fax: + 66 74 288395. ⁎⁎ Corresponding author. Tel.: + 66 53 943344; fax: + 66 53 892277. E-mail addresses: [email protected] (A. Phuruangrat), [email protected] (T. Thongtem). 0167-577X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2011.12.085
Glycols such as ethylene glycol, 1,2-propadiol and polyethylene glycol with different molecular weights (MWs) are novel solvents for synthesizing nanostructured materials with different morphologies [11–15]. In this research, the synthesis of Bi2S3 with different morphologies by glycolthermal method using ethylene glycol (EG), propylene glycol (PG), polyethylene glycol (PEG) with different MWs as solvents was reported. 2. Experiment All chemicals with analytical grade were used without further purification. In this experiment, 0.01 mol Bi(NO3)3·5H2O and 0.015 mol L-cysteine were dissolved in 75 ml of different glycol solvents including EG, PG and PEG with different MWs of 200, 300, 400 and 600 under 1 h vigorous stirring. PEG with MW of 200 was encoded as PEG-200, and similarly for others. Each solution was loaded into an 80 ml Teflon-lined stainless-steel autoclave. The autoclaves were tightly closed and put in an oven at 180 °C for 12 h. At the conclusion, deep gray precipitates were synthesized, repeatedly washed with distilled water and absolute ethanol, and dried in vacuum at 60 °C for 4 h for further characterization. 3. Results and discussion XRD patterns (Fig. 1) of the as-synthesized products in different glycols were indexed as pure orthorhombic Bi2S3 with Pbnm space group (JCPDS database no. 17-0320) [16] with its calculated lattice parameters [17] of 11.1300, 11.260 and 3.960 Å. Strong sharp reflection peaks indicated that well-crystallized products were synthesized through the glycolthermal process.
A. Phuruangrat et al. / Materials Letters 72 (2012) 104–106
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Fig. 3. TEM and HRTEM images, and SAED pattern of Bi2S3 nanowires synthesized in PG. Fig. 1. XRD patterns of Bi2S3 nanostructures synthesized in (a–d) EG, PG, PEG-300, and PEG-600, respectively.
TEM images (Fig. 2a–f) of Bi2S3 nanostructures synthesized in different solvents revealed different product morphologies. A large number of Bi2S3 nanorods and nanowires were synthesized in EG and PG, respectively. They were well segregated with 50 nm diameter and 200–1200 nm long for nanorods, and 50 nm diameter and as long as 4 μm for nanowires. It should be noted that no individual nanorods and nanowires were synthesized in other glycols, showing that EG and PG have the advantage in forming the segregated nanorods and nanowires. TEM image of the as-synthesized Bi2S3 in PEG-200 indicates that the product was a cluster of typical straw-sheaves, composed of high agglomeration of numerous nanorods with radial radiation out of their center. Each straw-sheaf was approximately 4 μm long. In this research, nanostructured microflowers composed of petals with different shapes and sizes were synthesized in PEG300, PEG-400 and PEG-600. Spherical Bi3S2 microflowers synthesized in PEG-300 were clearly detected. A number of nanoneedles radially
radiated from a common point to build up microflowers. Bi2S3 architecture synthesized in PEG-400 was composed of well-aligned nanorods pointed out of a common center to form 4 μm microflower. Upon increasing the MW of PEG to 600, a typical TEM image presents Bi2S3 microflowers of nanorods, growing out of centers. Each microflower consisted of nanorods with 20−50 nm diameter and several hundred nanometers long. In conclusion, different solvents played the key role in the formation of Bi2S3 nanostructures with different morphologies. Bi2S3 nanowires were further characterized by TEM, SAED and HRTEM (Fig. 3). Bi2S3 long uniform nanowires with 35 nm diameter growing along the c axis were detected. The HRTEM image, recorded on two different nanowires, revealed the presence of single crystalline nanowires with 3.96 Å lattice spacing of the (220) planes of orthorhombic Bi2S3 [16]. Due to lowest excess energy of the (001) planes than others [18], the nanowires preferentially grew along the [001] direction—in accordance with the previous report [19]. Bi2S3 microflower (Fig. 4a and b) shows an individual Bi2S3 flower-like structure with perfect geometry, assembled by tens of
Fig. 2. TEM images of Bi2S3 nanostructures synthesized in (a–f) EG, PG, PEG-200, PEG-300, PEG-400 and PEG-600, respectively.
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A. Phuruangrat et al. / Materials Letters 72 (2012) 104–106
Bi2S3 molecules of these two paths gradually nucleated, and provided as seeds for crystalline growing. Concurrently different templates (EG, PG, PEG-200, PEG-300, PEG-400 and PEG-600) modeled the growing Bi2S3 nuclei to be perfect nanorods, nanowires, straw-sheaves of nanorods, and microflowers of nanorods [1–3,20]. 4. Conclusions Nanorods, nanowires, straw-sheaves and microflowers of nanostructured orthorhombic Bi2S3 were synthesized by the 180 °C and 12 h glycolthermal reactions, and were found to be controlled by different solvents: EG, PG and PEG with different MWs. Acknowledgements We wish to thank the National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency, for providing financial support through the project code: P-10-11345, and the Thailand Research Fund through the TRF research grant. Fig. 4. TEM and HRTEM images, and SAED pattern of Bi2S3 nanowires synthesized in PEG-600.
uniform nanorods with 0.75–1 μm long and 40–80 nm diameter. SAED pattern (Fig. 4c) was indexed through the [010] electron beam direction and specified as orthorhombic Bi2S3 [16]. HRTEM image (Fig. 4d) of the individual Bi2S3 nanorod clearly presents 3.96 Å lattice spacing of orthorhombic Bi2S3 [16]. The Bi2S3 nanorod building up the flower-like structure was single crystal composed of the (220) parallel planes, and has the preferred growth along the [001] direction. Basing on the above, a formation mechanism of Bi2S3 with different morphologies was proposed. Although the exact mechanism is still unclear, the interaction between Bi3 + and S 2 − ions assumingly played a significant role in the formation of Bi2S3 nanostructures. Two paths were possible. (1) Initially, Bi3 + ions were solvated by glycol molecules. Afterwards S2 − ions synthesized from L-cysteine through the hydrolysis reaction might attack the Bi3 + ions, inducing the formation of bond between Bi3 + and S2 −. (2) Alternately, Bi 3 + ions might react with L-cysteine to form complexes. Subsequently, the complexes glycolthermally decomposed to form Bi2S3 molecules. During processing,
References [1] Tang C, Wang C, Su F, Zang C, Yang Y, Zong Z, et al. Solid State Sci 2010;12:1352–6. [2] Thongtem T, Pilapong C, Kavinchan J, Phuruangrat A, Thongtem S. J Alloy Compd 2010;500:195–9. [3] Zhu G, Liu P. Cryst Res Technol 2009;44:713–20. [4] Zhang D, Niu F, Yan T, Shi L, Du X, Fang J. Appl Surf Sci 2011;257:10161–7. [5] Pan C, Zhang D, Shi L, Fang J. Eur J Inorg Chem 2008;2008:2429–36. [6] Pan C, Zhang D, Shi L. J Solid State Chem 2008;181:1298–306. [7] Lu J, Han Q, Yang X, Lu L, Wang X. Mater Lett 2007;61:3425–8. [8] Begum A, Hussain A, Rahman A. Mater Sci Appl 2011;2:163–8. [9] Yu Y, Sun WT. Mater Lett 2009;63:1917–20. [10] Tang CJ, Zhang YX, Dou XC, Li GH. J Cryst Growth 2010;312:692–7. [11] Zhang D, Yan T, Shi L, Pan C, Zhang J. Appl Surf Sci 2009;255:5789–94. [12] Phuruangrat A, Ekthammathat N, Thongtem T, Thongtem S. J Alloy Compd 2011;509:10150–4. [13] Zhang D, Fu H, Shi L, Pan C, Li Q, Chu Y, et al. Inorg Chem 2007;46:2446–51. [14] Phuruangrat A, Thongtem T, Thongtem S. Appl Surf Sci 2008;254:7553–8. [15] Thongtem T, Phuruangrat A, Thongtem S. J Ceram Proc Res 2008;9:189–91. [16] Powder Diffract. File, JCPDS-ICDD, 12 Campus Boulevard, Newtown Square, PA 19073-3273, U.S.A. 2001. [17] Suryanarayana C, Norton MG. X-ray Diffract. NY: Plenum Press; 1998. [18] Phuruangrat A, Thongtem T, Thongtem S. Mater Lett 2009;63:1538–41. [19] Wang Y, Chen J, Wang P, Chen L, Chen YB, Wu LM. J Phys Chem C 2009;113: 16009–14. [20] Wu J, Qin F, Cheng G, Li H, Zhang J, Xie Y, et al. J Alloy Compd 2011;509:2116–26.
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Controlling morphologies of Bi2S3 nanostructures synthesized by glycolthermal method Anukorn Phuruangrat a,⁎, Somchai Thongtem b, Titipun Thongtem c,⁎⁎ a b c
Department of Materials Science and Technology, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand
a r t i c l e
i n f o
Article history: Received 14 September 2011 Accepted 22 December 2011 Available online 29 December 2011 Keywords: Semiconductors X-ray techniques Electron microscopy
a b s t r a c t Single crystalline orthorhombic Bi2S3 nanostructures with different morphologies were synthesized by the 180 °C and 12 h glycolthermal reactions, using ethylene glycol, propylene glycol and polyethylene glycol with different molecular weights as solvents. The as-synthesized products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED). In the present research, different solvents played the role in the product morphologies. A formation mechanism of Bi2S3 nanostructures was also proposed. © 2011 Elsevier B.V. All rights reserved.
1. Introduction Generally, nanostructured materials exhibit novel properties, comparing to their bulks due to their quantum confinement effect and number of free electrons. Much effort has been dedicated to achieve in controlling over the morphologies [1–3]. Among them, ceria nanospindles as a catalyst for oxidation of CO were synthesized via a simple template-free solvothermal treatment [4], large-scale synthesis of single-crystalline and uniform CeO2 nanorods by a precipitation method [5], and CeO2 nanoplates, nanotubes, and nanorods by CTAB assisted hydrothermal synthesis, including the study of their morphologies on the oxidation of CO [6]. Over the past decades, chalcogenide semiconductors (A2X3, A = Sb, Bi, As, and X = S, Se, Te) have received considerable attention due to their wide applications in television cameras with photoconducting targets, thermoelectric devices, optoelectronic devices, and IR spectroscopy photovoltaic converters, including their unique thermal, mechanical, electron transport, phonon transport, optical and non-linear optical properties [2,3,7]. Particularly, Bi2S3 is a low direct band gap (1.3–1.7 eV) layered semiconductor that crystallizes in orthorhombic system with a promising candidate for a number of applications. It has large absorption coefficient, and is an ideal candidate for solar cells and photodetectors in the visible region, including thermoelectric applications [2,7–10].
⁎ Corresponding author. Tel.: + 66 74 288374; fax: + 66 74 288395. ⁎⁎ Corresponding author. Tel.: + 66 53 943344; fax: + 66 53 892277. E-mail addresses: [email protected] (A. Phuruangrat), [email protected] (T. Thongtem). 0167-577X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2011.12.085
Glycols such as ethylene glycol, 1,2-propadiol and polyethylene glycol with different molecular weights (MWs) are novel solvents for synthesizing nanostructured materials with different morphologies [11–15]. In this research, the synthesis of Bi2S3 with different morphologies by glycolthermal method using ethylene glycol (EG), propylene glycol (PG), polyethylene glycol (PEG) with different MWs as solvents was reported. 2. Experiment All chemicals with analytical grade were used without further purification. In this experiment, 0.01 mol Bi(NO3)3·5H2O and 0.015 mol L-cysteine were dissolved in 75 ml of different glycol solvents including EG, PG and PEG with different MWs of 200, 300, 400 and 600 under 1 h vigorous stirring. PEG with MW of 200 was encoded as PEG-200, and similarly for others. Each solution was loaded into an 80 ml Teflon-lined stainless-steel autoclave. The autoclaves were tightly closed and put in an oven at 180 °C for 12 h. At the conclusion, deep gray precipitates were synthesized, repeatedly washed with distilled water and absolute ethanol, and dried in vacuum at 60 °C for 4 h for further characterization. 3. Results and discussion XRD patterns (Fig. 1) of the as-synthesized products in different glycols were indexed as pure orthorhombic Bi2S3 with Pbnm space group (JCPDS database no. 17-0320) [16] with its calculated lattice parameters [17] of 11.1300, 11.260 and 3.960 Å. Strong sharp reflection peaks indicated that well-crystallized products were synthesized through the glycolthermal process.
A. Phuruangrat et al. / Materials Letters 72 (2012) 104–106
105
Fig. 3. TEM and HRTEM images, and SAED pattern of Bi2S3 nanowires synthesized in PG. Fig. 1. XRD patterns of Bi2S3 nanostructures synthesized in (a–d) EG, PG, PEG-300, and PEG-600, respectively.
TEM images (Fig. 2a–f) of Bi2S3 nanostructures synthesized in different solvents revealed different product morphologies. A large number of Bi2S3 nanorods and nanowires were synthesized in EG and PG, respectively. They were well segregated with 50 nm diameter and 200–1200 nm long for nanorods, and 50 nm diameter and as long as 4 μm for nanowires. It should be noted that no individual nanorods and nanowires were synthesized in other glycols, showing that EG and PG have the advantage in forming the segregated nanorods and nanowires. TEM image of the as-synthesized Bi2S3 in PEG-200 indicates that the product was a cluster of typical straw-sheaves, composed of high agglomeration of numerous nanorods with radial radiation out of their center. Each straw-sheaf was approximately 4 μm long. In this research, nanostructured microflowers composed of petals with different shapes and sizes were synthesized in PEG300, PEG-400 and PEG-600. Spherical Bi3S2 microflowers synthesized in PEG-300 were clearly detected. A number of nanoneedles radially
radiated from a common point to build up microflowers. Bi2S3 architecture synthesized in PEG-400 was composed of well-aligned nanorods pointed out of a common center to form 4 μm microflower. Upon increasing the MW of PEG to 600, a typical TEM image presents Bi2S3 microflowers of nanorods, growing out of centers. Each microflower consisted of nanorods with 20−50 nm diameter and several hundred nanometers long. In conclusion, different solvents played the key role in the formation of Bi2S3 nanostructures with different morphologies. Bi2S3 nanowires were further characterized by TEM, SAED and HRTEM (Fig. 3). Bi2S3 long uniform nanowires with 35 nm diameter growing along the c axis were detected. The HRTEM image, recorded on two different nanowires, revealed the presence of single crystalline nanowires with 3.96 Å lattice spacing of the (220) planes of orthorhombic Bi2S3 [16]. Due to lowest excess energy of the (001) planes than others [18], the nanowires preferentially grew along the [001] direction—in accordance with the previous report [19]. Bi2S3 microflower (Fig. 4a and b) shows an individual Bi2S3 flower-like structure with perfect geometry, assembled by tens of
Fig. 2. TEM images of Bi2S3 nanostructures synthesized in (a–f) EG, PG, PEG-200, PEG-300, PEG-400 and PEG-600, respectively.
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A. Phuruangrat et al. / Materials Letters 72 (2012) 104–106
Bi2S3 molecules of these two paths gradually nucleated, and provided as seeds for crystalline growing. Concurrently different templates (EG, PG, PEG-200, PEG-300, PEG-400 and PEG-600) modeled the growing Bi2S3 nuclei to be perfect nanorods, nanowires, straw-sheaves of nanorods, and microflowers of nanorods [1–3,20]. 4. Conclusions Nanorods, nanowires, straw-sheaves and microflowers of nanostructured orthorhombic Bi2S3 were synthesized by the 180 °C and 12 h glycolthermal reactions, and were found to be controlled by different solvents: EG, PG and PEG with different MWs. Acknowledgements We wish to thank the National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency, for providing financial support through the project code: P-10-11345, and the Thailand Research Fund through the TRF research grant. Fig. 4. TEM and HRTEM images, and SAED pattern of Bi2S3 nanowires synthesized in PEG-600.
uniform nanorods with 0.75–1 μm long and 40–80 nm diameter. SAED pattern (Fig. 4c) was indexed through the [010] electron beam direction and specified as orthorhombic Bi2S3 [16]. HRTEM image (Fig. 4d) of the individual Bi2S3 nanorod clearly presents 3.96 Å lattice spacing of orthorhombic Bi2S3 [16]. The Bi2S3 nanorod building up the flower-like structure was single crystal composed of the (220) parallel planes, and has the preferred growth along the [001] direction. Basing on the above, a formation mechanism of Bi2S3 with different morphologies was proposed. Although the exact mechanism is still unclear, the interaction between Bi3 + and S 2 − ions assumingly played a significant role in the formation of Bi2S3 nanostructures. Two paths were possible. (1) Initially, Bi3 + ions were solvated by glycol molecules. Afterwards S2 − ions synthesized from L-cysteine through the hydrolysis reaction might attack the Bi3 + ions, inducing the formation of bond between Bi3 + and S2 −. (2) Alternately, Bi 3 + ions might react with L-cysteine to form complexes. Subsequently, the complexes glycolthermally decomposed to form Bi2S3 molecules. During processing,
References [1] Tang C, Wang C, Su F, Zang C, Yang Y, Zong Z, et al. Solid State Sci 2010;12:1352–6. [2] Thongtem T, Pilapong C, Kavinchan J, Phuruangrat A, Thongtem S. J Alloy Compd 2010;500:195–9. [3] Zhu G, Liu P. Cryst Res Technol 2009;44:713–20. [4] Zhang D, Niu F, Yan T, Shi L, Du X, Fang J. Appl Surf Sci 2011;257:10161–7. [5] Pan C, Zhang D, Shi L, Fang J. Eur J Inorg Chem 2008;2008:2429–36. [6] Pan C, Zhang D, Shi L. J Solid State Chem 2008;181:1298–306. [7] Lu J, Han Q, Yang X, Lu L, Wang X. Mater Lett 2007;61:3425–8. [8] Begum A, Hussain A, Rahman A. Mater Sci Appl 2011;2:163–8. [9] Yu Y, Sun WT. Mater Lett 2009;63:1917–20. [10] Tang CJ, Zhang YX, Dou XC, Li GH. J Cryst Growth 2010;312:692–7. [11] Zhang D, Yan T, Shi L, Pan C, Zhang J. Appl Surf Sci 2009;255:5789–94. [12] Phuruangrat A, Ekthammathat N, Thongtem T, Thongtem S. J Alloy Compd 2011;509:10150–4. [13] Zhang D, Fu H, Shi L, Pan C, Li Q, Chu Y, et al. Inorg Chem 2007;46:2446–51. [14] Phuruangrat A, Thongtem T, Thongtem S. Appl Surf Sci 2008;254:7553–8. [15] Thongtem T, Phuruangrat A, Thongtem S. J Ceram Proc Res 2008;9:189–91. [16] Powder Diffract. File, JCPDS-ICDD, 12 Campus Boulevard, Newtown Square, PA 19073-3273, U.S.A. 2001. [17] Suryanarayana C, Norton MG. X-ray Diffract. NY: Plenum Press; 1998. [18] Phuruangrat A, Thongtem T, Thongtem S. Mater Lett 2009;63:1538–41. [19] Wang Y, Chen J, Wang P, Chen L, Chen YB, Wu LM. J Phys Chem C 2009;113: 16009–14. [20] Wu J, Qin F, Cheng G, Li H, Zhang J, Xie Y, et al. J Alloy Compd 2011;509:2116–26.