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Solution-phase synthesis of Ag2S hollow and concave nanocubes
Inorganic Chemistry Communications 7 (2004) 359–362 www.elsevier.com/locate/inoche
Solution-phase synthesis of Ag2S hollow and concave nanocubes Mengdong Wu 1, Xinxin Pan, Xuefeng Qian *, Jie Yin, Zikang Zhu School of Chemistry and Chemical Technology, Research Institute of Polymer Materials, State Key Laboratory of Composite Materials, Shanghai Jiao Tong University, Shanghai 200240, PR China Received 29 November 2003; accepted 13 December 2003 Published online: 8 January 2004
Abstract Hollow and concave Ag2 S nanocubes have been prepared through the reaction of thioacetamide (TAA) and AgNO3 in carboxymethyl cellulose (CMC) aqueous solution. CMC acts as the templates and capping agents in the solution. The edge length of each cube was about 200 50 nm. Ó 2003 Elsevier B.V. All rights reserved. Keywords: Ag2 S; Nanocubes; Hollow; Concave
Recently, many efforts have been devoted to the morphological control of chalcogenide semiconductor nanocrystals owing to their technological importance [1–4]. As one of the most important chalcogenide, Ag2 S is a semiconductor that has potential applications as a photoelectric and thermoelectric material [5]. Ag2 S nanoparticles with different structures have been synthesized by various methods. For example, we and others have successfully prepared sphere or chain-like Ag2 S with the modification of polyvinylpyrrolidone (PVP) or not at room temperature [6,7]. Hollow nanoparticles are an interesting class of materials which are potentially useful for a wide range of applications and will help one to understand the relationship between morphology and property [8–12]. The preparation of hollow cubic nanostructure is very difficult. Hollow gold cubes have been made by etching the silver nanocubes with HAuCl4 [13]. To the best of our knowledge, the preparation of Ag2 S with hollow and concave cubic structure has never been reported. Herein, hollow and concave Ag2 S nanocubes were prepared through a onestep, facile process based on the reaction between
* Corresponding author. Tel.: +86-021-54743268; fax: +86-02154741297. E-mail address: [email protected] (X. Qian). 1 Tel.: +86-021-54743262; fax: +86-021-54741297.
1387-7003/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2003.12.016
AgNO3 and thioacetamide (TAA) in aqueous solution with the presence of carboxymethyl cellulose (CMC). In a typical process, 0.05 g CMC was dissolved into 10 ml water, then 5 ml of 4 103 M aqueous AgNO3 solution was added to the solution under magnetic stirring. After 3 h, 5 ml of 3 103 M aqueous TAA (50% excessive based on AgNO3 ) was added to the solution and the mixture was stirred in dark for sulfuration reaction for 3 h. This reaction mixture was then constantly heated at 80 °C for 8 h for the aging of Ag2 S particles and then cooled to room temperature naturally. The final products were obtained after being centrifuged and washed with water several times. The X-ray powder diffraction (XRD) patterns were recorded at a scanning rate of 4° min1 in the 2h range of 20–80° using a Rigaku D/max cC X-ray diffractom Fig. 1 shows eter with Cu-Ka radiation (k ¼ 1:54178 A). the typical XRD patterns of the obtained samples. All the diffraction peaks could be indexed to b-Ag2 S phase b0 ¼ 6:9 A, c0 ¼ 7:9 A. with cell constants a0 ¼ 4:3 A, TEM images were taken on a Hitachi model S-530 transmission electron microscope, using an accelerating voltage of 100 kv. SEM images were taken on a LEO model 1550 VP. From the TEM image of the Ag2 S (Fig. 2(a)), many cubic hollow structures could be observed and the edge length of each cube was about 200 50 nm. Interestingly, we could find some cubic structures with two or three holes in Fig. 2(a). We
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M. Wu et al. / Inorganic Chemistry Communications 7 (2004) 359–362
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121 022 112 013 103
134
213
223
031
111 012
200 103 131 123 212 014
111
500
120
112
1000 101
Intensity (a.u.)
1500
0 20
30
40
50
60
70
2 theta / degrees Fig. 1. XRD pattern of the Ag2 S particles synthesized at 80 °C.
Fig. 2. (a) TEM and (b) SEM images of hollow cubic Ag2 S particles synthesized at 80 °C.
speculate that, the hollow cubic structure has more than two outlets on its facet. From the SEM photograph (Fig. 2(b)), we could find that cubes have two holes on their adjacent facets. So the cubic structure prepared is
more like a ‘‘frame’’ structure, which is hollow inside and has holes on each side. The reaction temperature has great influence on the morphology of Ag2 S nanoparticles. When the solution was stirred at room temperature for 11 h after the introduction of TAA without changing the other conditions, concave cubic structures were obtained. From the TEM photographs (Fig. 3(a)) we found that, those particles were monodisperse with an edge length of 200 50 nm. From which we could also find that, the edges of these nanoparticles were darker than the central portions. We think that, each facet of cubic structure may be concave. The SEM photographs (Fig. 3(b)) further confirmed the speculation. Ultraviolet–visible (UV–Vis) spectra were measured on a Perkin–Elmer Lambda 20 UV–Vis spectrophotometer. UV–Vis spectra of the two samples, which were obtained from the supernates of Ag2 S powders redispersed in aqueous solution, are shown in Fig. 4. The spectra are broadened and the maximum absorption is on 261 and 286 nm, respectively. We could find that, the hollow Ag2 S nanocubes have more blue shift than the concave ones. This result is consistent with the phenomenon observed by Chad A. Mirkin and co-workers [8]. When they back-filled the hollow nanoframes to be nanoprisms, they observed red shift in the UV–Vis spectrum. The formation process of Ag2 S nanoparticles in CMC could be described as follows. When TAA was added to the CMC/Agþ solution, it gradually released sulfide ions upon decomposition, then combined with silver ions to form Ag2 S as described in Eqs. (1) and (2). CH3 CSNH2 ! CH3 CN þ H2 S
ð1Þ
2Agþ þ H2 S ! Ag2 S þ 2Hþ
ð2Þ
Although the exact formation mechanism of the Ag2 S hollow, concave cubic microstructure is unclear, we think that CMC plays a key role in the formation of cubic and chain like Ag2 S nanoparticles. As a biomacromolecule, CMC has rich carboxylate groups which could coordinate with Agþ in solution-phase. When CMC was introduced, the coordination between CMC and Agþ could determine the spatial site of nucleation and prevent the aggregation of initially formed Ag2 S particles due to the steric effect of CMC which can overlap and coil up to form micelle and serve as template to form the cubic structure [14]. The morphology of the product was also found to strongly depend on reaction conditions such as temperature. When the reaction was carried at low temperature (room temperature), the Ag2 S nanoparticle with concave microstructure was formed in the solution due to the effect of CMC. When the temperature is higher (80 °C), the solubility of CMC increases and the CMC micelle incorporated in the Ag2 S cubic begin to dissolve into
M. Wu et al. / Inorganic Chemistry Communications 7 (2004) 359–362
361
Fig. 3. (a) TEM and (b) SEM image of concave Ag2 S particles synthesized at room temperature.
2.2
a
2.0
b
Absorbance (a.u.)
1.8 1.6 1.4 1.2 1.0 0.8
solution gradually, and leading to the formation of hollow cubic microstructure of Ag2 S. In conclusion, concave and hollow Ag2 S nanocubes were successfully prepared through the reaction of AgNO3 and TAA with CMC as the template. Furthermore, as a biomacromolecular, CMC is nontoxic, cheap and can effectively control the Ag2 S morphology. We expect that, this convenient synthetic route to hollow Ag2 S nanocubes may be extended to the synthesis of other technologically important inorganic materials.
0.6 0.4 0.2
Acknowledgements 200
250 300 350 Wavelength (nm)
400
Fig. 4. UV–Vis spectra of Ag2 S particles synthesized at (a) 80 °C and (b) room temperature.
This work is financially supported by the National Nature Foundation of China (50103006), the Shanghai ShuGuang Project (01-SG-15) and the Shanghai Nanomaterials Project (0241nm106).
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M. Wu et al. / Inorganic Chemistry Communications 7 (2004) 359–362
References [1] S.-M. Lee, Y. Jun, S.-N. Cho, J. Cheon, J. Am. Chem. Soc. 124 (2002) 11244. [2] E.D. Sone, E.R. Zubarev, S.I. Stupp, Angew. Chem. Int. Ed. 41 (2002) 1706. [3] Z. Zhang, Q. Wu, Y. Ding, Inorg. Chem. Commun. 6 (2003) 1393–1394. [4] Y. Ni, F. Wang, H. Liu, Y. Liang, G. Yin, J. Hong, X. Ma, Z. Xu, Inorg. Chem. Commun. 6 (2003) 1406–1408. [5] C. Wang, X. Zhang, X. Qian, W. Wang, Y. Qian, Mater. Res. Bull. 33 (1998) 1083. [6] S. Liu, X. Qian, J. Yin, L. Hong, X. Wang, Z. Zhu, J. Solid State Chem. 168 (2002) 259.
[7] X. Qian, J. Yin, S. Feng, S. Liu, Z. Zhu, J. Mater. Chem. 11 (2001) 2504. [8] Gabriella S. Metraux, Yunwei Charles Cao, R. Jin, Chad A. Mirkin., Nano. Lett. 3 (2003) 519. [9] J. Zhu, S. Xu, H. Wang, J. Zhu, H. Chen, Adv. Mater. 15 (2003) 156. [10] Z. Zhong, Y. Yin, B. Gates, Y. Xia, Adv. Mater. 12 (2000) 206. [11] C.E. Fowler, D. Khushalani, S. Mann, Chem. Commun. (2001) 2028. [12] S.-W. Kim, M. Kim, W.Y. Lee, T. Hyeon, J. Am. Chem. Soc. 124 (2002) 7642. [13] Y. Sun, Y. Xia, Science 298 (2002) 2176. [14] U. Kastner, H. Hoffmann, R. Donges, J. Hilbig, Colloids Surf. A 123–124 (1997) 307–328.
Solution-phase synthesis of Ag2S hollow and concave nanocubes Mengdong Wu 1, Xinxin Pan, Xuefeng Qian *, Jie Yin, Zikang Zhu School of Chemistry and Chemical Technology, Research Institute of Polymer Materials, State Key Laboratory of Composite Materials, Shanghai Jiao Tong University, Shanghai 200240, PR China Received 29 November 2003; accepted 13 December 2003 Published online: 8 January 2004
Abstract Hollow and concave Ag2 S nanocubes have been prepared through the reaction of thioacetamide (TAA) and AgNO3 in carboxymethyl cellulose (CMC) aqueous solution. CMC acts as the templates and capping agents in the solution. The edge length of each cube was about 200 50 nm. Ó 2003 Elsevier B.V. All rights reserved. Keywords: Ag2 S; Nanocubes; Hollow; Concave
Recently, many efforts have been devoted to the morphological control of chalcogenide semiconductor nanocrystals owing to their technological importance [1–4]. As one of the most important chalcogenide, Ag2 S is a semiconductor that has potential applications as a photoelectric and thermoelectric material [5]. Ag2 S nanoparticles with different structures have been synthesized by various methods. For example, we and others have successfully prepared sphere or chain-like Ag2 S with the modification of polyvinylpyrrolidone (PVP) or not at room temperature [6,7]. Hollow nanoparticles are an interesting class of materials which are potentially useful for a wide range of applications and will help one to understand the relationship between morphology and property [8–12]. The preparation of hollow cubic nanostructure is very difficult. Hollow gold cubes have been made by etching the silver nanocubes with HAuCl4 [13]. To the best of our knowledge, the preparation of Ag2 S with hollow and concave cubic structure has never been reported. Herein, hollow and concave Ag2 S nanocubes were prepared through a onestep, facile process based on the reaction between
* Corresponding author. Tel.: +86-021-54743268; fax: +86-02154741297. E-mail address: [email protected] (X. Qian). 1 Tel.: +86-021-54743262; fax: +86-021-54741297.
1387-7003/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2003.12.016
AgNO3 and thioacetamide (TAA) in aqueous solution with the presence of carboxymethyl cellulose (CMC). In a typical process, 0.05 g CMC was dissolved into 10 ml water, then 5 ml of 4 103 M aqueous AgNO3 solution was added to the solution under magnetic stirring. After 3 h, 5 ml of 3 103 M aqueous TAA (50% excessive based on AgNO3 ) was added to the solution and the mixture was stirred in dark for sulfuration reaction for 3 h. This reaction mixture was then constantly heated at 80 °C for 8 h for the aging of Ag2 S particles and then cooled to room temperature naturally. The final products were obtained after being centrifuged and washed with water several times. The X-ray powder diffraction (XRD) patterns were recorded at a scanning rate of 4° min1 in the 2h range of 20–80° using a Rigaku D/max cC X-ray diffractom Fig. 1 shows eter with Cu-Ka radiation (k ¼ 1:54178 A). the typical XRD patterns of the obtained samples. All the diffraction peaks could be indexed to b-Ag2 S phase b0 ¼ 6:9 A, c0 ¼ 7:9 A. with cell constants a0 ¼ 4:3 A, TEM images were taken on a Hitachi model S-530 transmission electron microscope, using an accelerating voltage of 100 kv. SEM images were taken on a LEO model 1550 VP. From the TEM image of the Ag2 S (Fig. 2(a)), many cubic hollow structures could be observed and the edge length of each cube was about 200 50 nm. Interestingly, we could find some cubic structures with two or three holes in Fig. 2(a). We
360
M. Wu et al. / Inorganic Chemistry Communications 7 (2004) 359–362
2000
121 022 112 013 103
134
213
223
031
111 012
200 103 131 123 212 014
111
500
120
112
1000 101
Intensity (a.u.)
1500
0 20
30
40
50
60
70
2 theta / degrees Fig. 1. XRD pattern of the Ag2 S particles synthesized at 80 °C.
Fig. 2. (a) TEM and (b) SEM images of hollow cubic Ag2 S particles synthesized at 80 °C.
speculate that, the hollow cubic structure has more than two outlets on its facet. From the SEM photograph (Fig. 2(b)), we could find that cubes have two holes on their adjacent facets. So the cubic structure prepared is
more like a ‘‘frame’’ structure, which is hollow inside and has holes on each side. The reaction temperature has great influence on the morphology of Ag2 S nanoparticles. When the solution was stirred at room temperature for 11 h after the introduction of TAA without changing the other conditions, concave cubic structures were obtained. From the TEM photographs (Fig. 3(a)) we found that, those particles were monodisperse with an edge length of 200 50 nm. From which we could also find that, the edges of these nanoparticles were darker than the central portions. We think that, each facet of cubic structure may be concave. The SEM photographs (Fig. 3(b)) further confirmed the speculation. Ultraviolet–visible (UV–Vis) spectra were measured on a Perkin–Elmer Lambda 20 UV–Vis spectrophotometer. UV–Vis spectra of the two samples, which were obtained from the supernates of Ag2 S powders redispersed in aqueous solution, are shown in Fig. 4. The spectra are broadened and the maximum absorption is on 261 and 286 nm, respectively. We could find that, the hollow Ag2 S nanocubes have more blue shift than the concave ones. This result is consistent with the phenomenon observed by Chad A. Mirkin and co-workers [8]. When they back-filled the hollow nanoframes to be nanoprisms, they observed red shift in the UV–Vis spectrum. The formation process of Ag2 S nanoparticles in CMC could be described as follows. When TAA was added to the CMC/Agþ solution, it gradually released sulfide ions upon decomposition, then combined with silver ions to form Ag2 S as described in Eqs. (1) and (2). CH3 CSNH2 ! CH3 CN þ H2 S
ð1Þ
2Agþ þ H2 S ! Ag2 S þ 2Hþ
ð2Þ
Although the exact formation mechanism of the Ag2 S hollow, concave cubic microstructure is unclear, we think that CMC plays a key role in the formation of cubic and chain like Ag2 S nanoparticles. As a biomacromolecule, CMC has rich carboxylate groups which could coordinate with Agþ in solution-phase. When CMC was introduced, the coordination between CMC and Agþ could determine the spatial site of nucleation and prevent the aggregation of initially formed Ag2 S particles due to the steric effect of CMC which can overlap and coil up to form micelle and serve as template to form the cubic structure [14]. The morphology of the product was also found to strongly depend on reaction conditions such as temperature. When the reaction was carried at low temperature (room temperature), the Ag2 S nanoparticle with concave microstructure was formed in the solution due to the effect of CMC. When the temperature is higher (80 °C), the solubility of CMC increases and the CMC micelle incorporated in the Ag2 S cubic begin to dissolve into
M. Wu et al. / Inorganic Chemistry Communications 7 (2004) 359–362
361
Fig. 3. (a) TEM and (b) SEM image of concave Ag2 S particles synthesized at room temperature.
2.2
a
2.0
b
Absorbance (a.u.)
1.8 1.6 1.4 1.2 1.0 0.8
solution gradually, and leading to the formation of hollow cubic microstructure of Ag2 S. In conclusion, concave and hollow Ag2 S nanocubes were successfully prepared through the reaction of AgNO3 and TAA with CMC as the template. Furthermore, as a biomacromolecular, CMC is nontoxic, cheap and can effectively control the Ag2 S morphology. We expect that, this convenient synthetic route to hollow Ag2 S nanocubes may be extended to the synthesis of other technologically important inorganic materials.
0.6 0.4 0.2
Acknowledgements 200
250 300 350 Wavelength (nm)
400
Fig. 4. UV–Vis spectra of Ag2 S particles synthesized at (a) 80 °C and (b) room temperature.
This work is financially supported by the National Nature Foundation of China (50103006), the Shanghai ShuGuang Project (01-SG-15) and the Shanghai Nanomaterials Project (0241nm106).
362
M. Wu et al. / Inorganic Chemistry Communications 7 (2004) 359–362
References [1] S.-M. Lee, Y. Jun, S.-N. Cho, J. Cheon, J. Am. Chem. Soc. 124 (2002) 11244. [2] E.D. Sone, E.R. Zubarev, S.I. Stupp, Angew. Chem. Int. Ed. 41 (2002) 1706. [3] Z. Zhang, Q. Wu, Y. Ding, Inorg. Chem. Commun. 6 (2003) 1393–1394. [4] Y. Ni, F. Wang, H. Liu, Y. Liang, G. Yin, J. Hong, X. Ma, Z. Xu, Inorg. Chem. Commun. 6 (2003) 1406–1408. [5] C. Wang, X. Zhang, X. Qian, W. Wang, Y. Qian, Mater. Res. Bull. 33 (1998) 1083. [6] S. Liu, X. Qian, J. Yin, L. Hong, X. Wang, Z. Zhu, J. Solid State Chem. 168 (2002) 259.
[7] X. Qian, J. Yin, S. Feng, S. Liu, Z. Zhu, J. Mater. Chem. 11 (2001) 2504. [8] Gabriella S. Metraux, Yunwei Charles Cao, R. Jin, Chad A. Mirkin., Nano. Lett. 3 (2003) 519. [9] J. Zhu, S. Xu, H. Wang, J. Zhu, H. Chen, Adv. Mater. 15 (2003) 156. [10] Z. Zhong, Y. Yin, B. Gates, Y. Xia, Adv. Mater. 12 (2000) 206. [11] C.E. Fowler, D. Khushalani, S. Mann, Chem. Commun. (2001) 2028. [12] S.-W. Kim, M. Kim, W.Y. Lee, T. Hyeon, J. Am. Chem. Soc. 124 (2002) 7642. [13] Y. Sun, Y. Xia, Science 298 (2002) 2176. [14] U. Kastner, H. Hoffmann, R. Donges, J. Hilbig, Colloids Surf. A 123–124 (1997) 307–328.