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Novel polyol route to AgBiS2 nanorods
Journal of Crystal Growth 252 (2003) 199–201
Novel polyol route to AgBiS2 nanorods Guozhen Shen, Di Chen, Kaibin Tang*, Yitai Qian Department of Chemistry and Structure Research Laboratory, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China Received 2 August 2002; accepted 2 December 2002 Communicated by L.F. Schneemeyer
Abstract The direct polyol method is used to prepare silver bismuth sulfide AgBiS2 nanorods. X-ray powder diffraction ( Transmission electron microscopy images reveal patterns indicate that AgBiS2 is cubic with a cell constant a ¼ 5:651 A. that the product consists of uniform rod-like crystals with diameters of about 40 nm and lengths up to 10 mm. A possible formation mechanism of silver bismuth sulfide is proposed. r 2003 Elsevier Science B.V. All rights reserved. PACS: 61.10.Nz; 81.10.Dn Keywords: A1. Low dimensional structures; A2. Growth from solutions; B1. Sulfides
In recent years, due to the continuing need for time-saving and energy-efficient techniques, the necessity to avoid competing reactions, and the synthesis of metastable phases, materials and chemistry researchers have paid more and more attention to the development of new routes to synthesize solid materials [1]. The polyol method has proved very attractive with regard to the preparation of nanoscale metal and oxide particles, and has been used to synthesize binary metal chalcogenide components [2–4]. Unfortunately, all these are conducted under either microwave irradiation or special high pressure. Recently, Feldmann et al. reported the direct polyol route to binary sulfides MS (M=Cd, Zn, Hg), which needs no special equipment or complex procedure *Corresponding author. Tel./fax: +86-551-360-1600. E-mail address: [email protected] (K. Tang).
[5]. But no report could be found on the synthesis of nanocrystallines ternary sulfide by this route. Herein, we try to extend the direct polyol route to nanocrystalline ternary sulfide and AgBiS2 nanorods were successfully synthesized, for the first time, by this novel route. To our knowledge, the ternary metal chalcogenide AgBiS2 belongs to the class of I–V–VI semiconducting materials, which are technologically important in linear, nonlinear, optoelectronic, and thermoelectric devices as well as optical recording media [6,7]. Traditionally, AgBiS2 can be prepared through solid-state reactions, solid solution techniques, and flux techniques. Our group has also developed solvothermal route [8–11]. In this paper, we report for the first time the synthesis of AgBiS2 nanorods via a direct low temperature polyol route, using AgNO3, Bi(NO3)3 and thiourea as the reactants.
0022-0248/03/$ - see front matter r 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0022-0248(02)02500-9
G. Shen et al. / Journal of Crystal Growth 252 (2003) 199–201
200
20
30
40
50
(004)
(113) (222)
(022)
(111)
Intensity (a.u.)
(002)
In a typical procedure, the appropriate amount of analytical grade AgNO3, Bi(NO3)3 and thiourea were added to a 100 ml flask. Filled with 50 ml glycol, the flask was heated and refluxed at 1951C for 1–2 h. After the mixture had cooled, the solid was filtered and washed several times with carbon bisulfide, absolute alcohol and distilled water, then vacuum dried at 601C for 3 h. the resulting product was black. The as-obtained sample was characterized by powder X-ray diffraction (XRD) performed on a Rigaku Dmax gA X-ray diffractometer with graphite-monochromated Cu Ka radiation ( Fig. 1 shows a XRD pattern of (l ¼ 1:54178 A). AgBiS2 sample prepared by the polyol mediated synthesis process. All the peaks can be indexed to the cubic phase of AgBiS2 with a cell constant of ( in agreement with reported data a ¼ 5:651 A, (JCPDS Card No. 21-1178). No characteristic peaks of other impurities such as Ag2S or Bi2S3 were observed. The composition of the product was determined by volumetric and gravimetric wet chemical analysis. The 0.300 g as-obtained sample consists of 0.7770 mmol of Ag, 0.7735 mmol of Bi and 1.529 mmol of S. The analysis gave a molar ratio of 1:0.996:1.968 Ag:Bi:S for the sample, by which the composition of the as-prepared AgBiS2 was determined to be AgBi0.996S1.968. The result confirms the formation of AgBiS2. The yield and morphology of prepared AgBiS2 nanorods were studied by scanning electron
60
2θ (degree)
Fig. 1. XRD pattern of AgBiS2.
70
Fig. 2. SEM image of obtained AgBiS2.
Fig. 3. (a) TEM image of obtained AgBiS2 nanorods; (b) ED pattern of AgBiS2 nanorod.
microscopy (SEM) (Fig. 2). The SEM image, which was performed on an AMRAY1000B scanning electron microanalyzer, reveals the appearance of nanorods with diameters range from 20 to 90 nm. The morphology and size of the product were further analyzed by transmission electron microscopy (TEM). TEM was taken on a Hitachi H-800 transmission electron microscope, using an accelerating voltage of 200 kV. The typical size of AgBiS2 nanorod observed by TEM is about 40 nm in diameter and length up to 10 mm. The representative ED pattern (Fig. 3b) shows its single-crystal nature.
G. Shen et al. / Journal of Crystal Growth 252 (2003) 199–201
The use of a suitable polyol as the solvent is undoubtedly vital in the formation of rodlike AgBiS2 crystallines. For comparison, different polyols were tested and the results showed that glycol was the optimum solvent. When glycerine, a high viscosity solvent with high boiling point, was used, only Bi2S3 with small amount of AgBiS2 was obtained. Using other polyols leads to similar results. The experimental results demonstrate that glycol plays an important role in the formation of phase pure AgBiS2 nanorods. Prior to our work, the literature has reported that many metal ions can complex with thiourea in alcohols to form metal-thiourea complexes [12,13]. In the present route, our observation confirmed that AgNO3 and Bi(NO3)3 were also dissolved in the thiourea solution. So, it is believed that Agthiourea and Bi-thiourea complexes formed in solution. On the basis of this, we propose a mechanism for the formation of AgBiS2 nanorods. The whole process can be expressed as the following: AgNO3 þ Tu-Ag2Tu
ðTu ¼ thioureaÞ
ð1Þ
BiðNO3 Þ3 þ Tu-Bi2Tu
ð2Þ
Ag2Tu þ Bi2Tu-AgBiS2
ð3Þ
First, the formation of Ag-thiourea and Bithiourea complexes prevent the formation of Ag2S and Bi2S3 because of few free ions, Ag+, Bi3+, S2, in the solution. Second, the Ag-thiourea and Bi-thiourea complexes undergo thermal decomposition at reaction temperature to produce AgBiS2 nanorods. At this stage, due to the relative stability of the complexes, decomposition will proceed more slowly and produce a smaller number of nuclei in the solution than the direct ion-exchange reaction. And at the same time, the boiling glycol makes these newly formed nuclei mix homogeneously, which may promote the oriented growth of the nanorods [14]. Although the proposed mechanism has been reported in literature [14], the exact mechanism of the M-thiourea and the reaction media on the
201
morphology of the crystals still remains obscure and further investigation is undoubtedly needed. In summary, we succeeded in synthesizing AgBiS2 nanorods via a simple direct polyol method. Compared with other methods, this route is a more effective, convenient, less energydemanding and time-saving technique and it is reasonable to expect the method to be useful for the synthesis of other one-dimensional ternary sulfides.
Acknowledgements Financial support from National Natural Science Foundation of China and the 973 Porjects of China is appreciated. We thank Prof. Zhou Geien, Fang Zhiqun, Liu Xianming, and Zhang Weizhen for helpful discussions.
References [1] C.N. Rao, Chemical Approaches to the Synthesis of Inorganic Materials, Wiley Eastern Limited, New Delhi, India, 1994, p. 1. [2] H. Grisaru, O. Palchik, A. Gedanken, V. Palchik, M.A. Weiss, J. Mater. Chem. 12 (2002) 339. [3] J. Zhu, S. Liu, O. Palchik, Y. Koltypin, A. Gedanken, J. Solid State. Chem. 153 (2000) 342. [4] O. Palchik, R. Kerner, J. Zhu, A. Gedanken, J. Solid State Chem. 154 (2000) 530. [5] C. Feldmann, C. Metzmacher, J. Mater. Chem. 11 (2001) 2603. [6] L.K. Snmanta, S. Chatterjee, Phys. Stat. Sol. B 182 (1994) 85. [7] S.A. Aliev, S.S. Raginov, Neorg. Mater. 28 (1992) 329. [8] H.S.G. Kullerud, Econ. Geol 54 (1959) 533. [9] G.H. Moh, L.A. Taylor, Neues Jahrb Mineral. H 9 (1971) 405. [10] L.T. Bryndzia, O.J. Kleppa, Econ. Geol 83 (1988) 174. [11] B. Xie, S.W. Yuan, Y. Jiang, J. Lu, Q. Li, Y. Wu, W.C. Yu, H.B. Zhang, Y.T. Qian, Chem. Lett. 31 (2002) 612. [12] M.K. Karanjai, D. Dasgupta, Thin Solid Films 155 (1987) 309. [13] N. Tohge, M. Asuka, T. Minami, J. Non-Cryst. Solids 147–148 (1992) 652. [14] J.Q. Hu, B. Deng, W.X. Zhang, K.B. Tang, Y.T. Qian, Int. J. Inorg. Mater. 3 (2001) 639.
Novel polyol route to AgBiS2 nanorods Guozhen Shen, Di Chen, Kaibin Tang*, Yitai Qian Department of Chemistry and Structure Research Laboratory, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China Received 2 August 2002; accepted 2 December 2002 Communicated by L.F. Schneemeyer
Abstract The direct polyol method is used to prepare silver bismuth sulfide AgBiS2 nanorods. X-ray powder diffraction ( Transmission electron microscopy images reveal patterns indicate that AgBiS2 is cubic with a cell constant a ¼ 5:651 A. that the product consists of uniform rod-like crystals with diameters of about 40 nm and lengths up to 10 mm. A possible formation mechanism of silver bismuth sulfide is proposed. r 2003 Elsevier Science B.V. All rights reserved. PACS: 61.10.Nz; 81.10.Dn Keywords: A1. Low dimensional structures; A2. Growth from solutions; B1. Sulfides
In recent years, due to the continuing need for time-saving and energy-efficient techniques, the necessity to avoid competing reactions, and the synthesis of metastable phases, materials and chemistry researchers have paid more and more attention to the development of new routes to synthesize solid materials [1]. The polyol method has proved very attractive with regard to the preparation of nanoscale metal and oxide particles, and has been used to synthesize binary metal chalcogenide components [2–4]. Unfortunately, all these are conducted under either microwave irradiation or special high pressure. Recently, Feldmann et al. reported the direct polyol route to binary sulfides MS (M=Cd, Zn, Hg), which needs no special equipment or complex procedure *Corresponding author. Tel./fax: +86-551-360-1600. E-mail address: [email protected] (K. Tang).
[5]. But no report could be found on the synthesis of nanocrystallines ternary sulfide by this route. Herein, we try to extend the direct polyol route to nanocrystalline ternary sulfide and AgBiS2 nanorods were successfully synthesized, for the first time, by this novel route. To our knowledge, the ternary metal chalcogenide AgBiS2 belongs to the class of I–V–VI semiconducting materials, which are technologically important in linear, nonlinear, optoelectronic, and thermoelectric devices as well as optical recording media [6,7]. Traditionally, AgBiS2 can be prepared through solid-state reactions, solid solution techniques, and flux techniques. Our group has also developed solvothermal route [8–11]. In this paper, we report for the first time the synthesis of AgBiS2 nanorods via a direct low temperature polyol route, using AgNO3, Bi(NO3)3 and thiourea as the reactants.
0022-0248/03/$ - see front matter r 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0022-0248(02)02500-9
G. Shen et al. / Journal of Crystal Growth 252 (2003) 199–201
200
20
30
40
50
(004)
(113) (222)
(022)
(111)
Intensity (a.u.)
(002)
In a typical procedure, the appropriate amount of analytical grade AgNO3, Bi(NO3)3 and thiourea were added to a 100 ml flask. Filled with 50 ml glycol, the flask was heated and refluxed at 1951C for 1–2 h. After the mixture had cooled, the solid was filtered and washed several times with carbon bisulfide, absolute alcohol and distilled water, then vacuum dried at 601C for 3 h. the resulting product was black. The as-obtained sample was characterized by powder X-ray diffraction (XRD) performed on a Rigaku Dmax gA X-ray diffractometer with graphite-monochromated Cu Ka radiation ( Fig. 1 shows a XRD pattern of (l ¼ 1:54178 A). AgBiS2 sample prepared by the polyol mediated synthesis process. All the peaks can be indexed to the cubic phase of AgBiS2 with a cell constant of ( in agreement with reported data a ¼ 5:651 A, (JCPDS Card No. 21-1178). No characteristic peaks of other impurities such as Ag2S or Bi2S3 were observed. The composition of the product was determined by volumetric and gravimetric wet chemical analysis. The 0.300 g as-obtained sample consists of 0.7770 mmol of Ag, 0.7735 mmol of Bi and 1.529 mmol of S. The analysis gave a molar ratio of 1:0.996:1.968 Ag:Bi:S for the sample, by which the composition of the as-prepared AgBiS2 was determined to be AgBi0.996S1.968. The result confirms the formation of AgBiS2. The yield and morphology of prepared AgBiS2 nanorods were studied by scanning electron
60
2θ (degree)
Fig. 1. XRD pattern of AgBiS2.
70
Fig. 2. SEM image of obtained AgBiS2.
Fig. 3. (a) TEM image of obtained AgBiS2 nanorods; (b) ED pattern of AgBiS2 nanorod.
microscopy (SEM) (Fig. 2). The SEM image, which was performed on an AMRAY1000B scanning electron microanalyzer, reveals the appearance of nanorods with diameters range from 20 to 90 nm. The morphology and size of the product were further analyzed by transmission electron microscopy (TEM). TEM was taken on a Hitachi H-800 transmission electron microscope, using an accelerating voltage of 200 kV. The typical size of AgBiS2 nanorod observed by TEM is about 40 nm in diameter and length up to 10 mm. The representative ED pattern (Fig. 3b) shows its single-crystal nature.
G. Shen et al. / Journal of Crystal Growth 252 (2003) 199–201
The use of a suitable polyol as the solvent is undoubtedly vital in the formation of rodlike AgBiS2 crystallines. For comparison, different polyols were tested and the results showed that glycol was the optimum solvent. When glycerine, a high viscosity solvent with high boiling point, was used, only Bi2S3 with small amount of AgBiS2 was obtained. Using other polyols leads to similar results. The experimental results demonstrate that glycol plays an important role in the formation of phase pure AgBiS2 nanorods. Prior to our work, the literature has reported that many metal ions can complex with thiourea in alcohols to form metal-thiourea complexes [12,13]. In the present route, our observation confirmed that AgNO3 and Bi(NO3)3 were also dissolved in the thiourea solution. So, it is believed that Agthiourea and Bi-thiourea complexes formed in solution. On the basis of this, we propose a mechanism for the formation of AgBiS2 nanorods. The whole process can be expressed as the following: AgNO3 þ Tu-Ag2Tu
ðTu ¼ thioureaÞ
ð1Þ
BiðNO3 Þ3 þ Tu-Bi2Tu
ð2Þ
Ag2Tu þ Bi2Tu-AgBiS2
ð3Þ
First, the formation of Ag-thiourea and Bithiourea complexes prevent the formation of Ag2S and Bi2S3 because of few free ions, Ag+, Bi3+, S2, in the solution. Second, the Ag-thiourea and Bi-thiourea complexes undergo thermal decomposition at reaction temperature to produce AgBiS2 nanorods. At this stage, due to the relative stability of the complexes, decomposition will proceed more slowly and produce a smaller number of nuclei in the solution than the direct ion-exchange reaction. And at the same time, the boiling glycol makes these newly formed nuclei mix homogeneously, which may promote the oriented growth of the nanorods [14]. Although the proposed mechanism has been reported in literature [14], the exact mechanism of the M-thiourea and the reaction media on the
201
morphology of the crystals still remains obscure and further investigation is undoubtedly needed. In summary, we succeeded in synthesizing AgBiS2 nanorods via a simple direct polyol method. Compared with other methods, this route is a more effective, convenient, less energydemanding and time-saving technique and it is reasonable to expect the method to be useful for the synthesis of other one-dimensional ternary sulfides.
Acknowledgements Financial support from National Natural Science Foundation of China and the 973 Porjects of China is appreciated. We thank Prof. Zhou Geien, Fang Zhiqun, Liu Xianming, and Zhang Weizhen for helpful discussions.
References [1] C.N. Rao, Chemical Approaches to the Synthesis of Inorganic Materials, Wiley Eastern Limited, New Delhi, India, 1994, p. 1. [2] H. Grisaru, O. Palchik, A. Gedanken, V. Palchik, M.A. Weiss, J. Mater. Chem. 12 (2002) 339. [3] J. Zhu, S. Liu, O. Palchik, Y. Koltypin, A. Gedanken, J. Solid State. Chem. 153 (2000) 342. [4] O. Palchik, R. Kerner, J. Zhu, A. Gedanken, J. Solid State Chem. 154 (2000) 530. [5] C. Feldmann, C. Metzmacher, J. Mater. Chem. 11 (2001) 2603. [6] L.K. Snmanta, S. Chatterjee, Phys. Stat. Sol. B 182 (1994) 85. [7] S.A. Aliev, S.S. Raginov, Neorg. Mater. 28 (1992) 329. [8] H.S.G. Kullerud, Econ. Geol 54 (1959) 533. [9] G.H. Moh, L.A. Taylor, Neues Jahrb Mineral. H 9 (1971) 405. [10] L.T. Bryndzia, O.J. Kleppa, Econ. Geol 83 (1988) 174. [11] B. Xie, S.W. Yuan, Y. Jiang, J. Lu, Q. Li, Y. Wu, W.C. Yu, H.B. Zhang, Y.T. Qian, Chem. Lett. 31 (2002) 612. [12] M.K. Karanjai, D. Dasgupta, Thin Solid Films 155 (1987) 309. [13] N. Tohge, M. Asuka, T. Minami, J. Non-Cryst. Solids 147–148 (1992) 652. [14] J.Q. Hu, B. Deng, W.X. Zhang, K.B. Tang, Y.T. Qian, Int. J. Inorg. Mater. 3 (2001) 639.