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Preparation and characterization of single-crystalline bismuth nanowires by a low-temperature solvothermal process
Chemical Physics Letters 367 (2003) 141–144 www.elsevier.com/locate/cplett
Preparation and characterization of single-crystalline bismuth nanowires by a low-temperature solvothermal process Yuanhao Gao 1, Helin Niu, Chuan Zeng, Qianwang Chen
*
Structure Research Laboratory, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, PR China Received 15 July 2002
Abstract Single-crystalline metallic bismuth nanowires have been successfully prepared by a solvothermal process at low temperatures, using aqueous bismuth nitrate ½BiðNO3 Þ3 5H2 O and ethylene diamine ðH2 NCH2 CH2 NH2 Þ as starting materials. Characterizations have been carried out by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The diameter of the nanowires is about 20–30 nm and lengths range from 0.2 to 2:5 lm. The reduction of bismuth ions (Bi3þ ) and formation mechanism of nanowire were discussed based on the characteristic of the reaction system employed. Ó 2002 Elsevier Science B.V. All rights reserved.
1. Introduction Over the past several years, one-dimensional nanostructures including nanotubes [1–4], nanorods [5,6] and nanowires [7–10], have received considerable attention from the scientific community. Much effort has been carried out on understanding the electronic [4,11], magnetic [12], and optical [13] properties of these nanostructures because they exhibit novel physical and chemical properties different from their bulk counterparts due to their reduced sizes and large surface-to*
Corresponding author. Fax: +86-551-3607292. E-mail address: [email protected] (Q. Chen). 1 Present address: Department of Chemistry, PingDingShan Teachers College, Henan, China, Visiting Scholar in the University of Science and Technology of China.
volume ratio [1]. These one-dimensional nanostructures are also promising candidates for realizing nanoscale electronic [14], optical [13], and mechanical [1] devices because they retain wire-like connectivity despite their nanoscale radial dimension. To date, most synthetic efforts have been directed toward carbon nanotubes [3,4], semiconductor [6–8], metallic [5], and binary oxide [9,10] nanotubes and nanowires. It is known that bismuth has small effective mass (0:001m0 ) and large mean-free path (0.4 mm at 4 K), which makes Bi nanowire become an interesting system for studying quantum confinement effects [15,16]. In addition, nanoscale bismuth materials have been recently suggested to be responsible for the enhancement of thermoelectric properties at room temperature [17,18]. However, owing to the relatively low-melting point of Bi (271.3 °C), the
0009-2614/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII: S 0 0 0 9 - 2 6 1 4 ( 0 2 ) 0 1 6 8 0 - 9
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synthesis of Bi nanowires is much more difficult [19]. Most of the existing high-temperature approaches, such as laser ablation [20], plasma-arc [21], or chemical vapor-phase synthesis [22–24] are inappropriate for synthesis of Bi nanowires. Hence, the investigations of rational synthesis, physical properties, and applications of the Bi nanowires remain as challenges to materials scientists. Here we report the synthesis of singlecrystalline metallic bismuth nanowires by a lowtemperature solvothermal process, using aqueous bismuth nitrate ½BiðNO3 Þ3 5H2 O and ethylene diamine as starting materials.
2. Experimental For the present experiment, the solvothermal technique is used to prepare Bi nanowires. The whole system consists of aqueous bismuth nitrate BiðNO3 Þ3 5H2 O, ethylene diamine and acetone. Two grams analytically pure aqueous bismuth nitrate BiðNO3 Þ3 5H2 O and 5 ml acetone were put into 40 ml pure ethylene diamine at room temperature to form a mixture with insoluble precipitate. The mixture was stirred strongly for 10 min and transferred into a stainless steel autoclave with inner Teflon vessel (volume, 80 ml). The autoclave was closed tightly to perform solvothermal process for 6 h at 160 °C. After the process, the obtained black product was washed with alcohol and distilled water three times, respectively, dried in air at 50 °C for 0.5 h. The sample was examined by XRD using a 18KW advanced X-ray diffractometer with ). The nanostrucCu Ka radiation (k ¼ 1:54056 A ture of as-prepared products was studied by TEM at an accelerating voltage of 200 kV.
3. Results and discussion Fig. 1 shows XRD pattern of the product. Compared the d values (d ¼ 3:9449, 3.7294, 3.2758, 2.3647, 2.2696, 2.0291, 1.9706, 1.8661, ) with 1.6386, 1.5547, 1.4900, 1.4419, 1.3861 A those in standard JCPDS cards (JCPDS, 05-0519), the peaks can be well indexed with the reflections of (0 0 3), (0 1 1), (1 0 2), (0 1 4), (1 1 0), (1 0 5),
Fig. 1. A typical XRD pattern of the obtained product.
(1 1 3), (0 2 2), (2 0 4), (0 1 7), (1 1 6), (2 1 2), (1 0 8) of Bi rhombohedral phase [space group: R3m (166)]. Lattice constants calculated from the dif and c ¼ 11:848 A , fraction data are a ¼ 4:552 A which are compatible with the literature values , c ¼ 11:852 A ). This XRD pattern (a ¼ 4:546 A indicates that the reduction of Bi3þ to elemental Bi is complete under current synthetic condition, consequently, pure metal Bi products were obtained. It is found that no or poor crystallinity elementary Bi was obtained under conditions of lower temperatures and shorter reaction times. For example, when the reaction was carried out at 130°C for 6 h, very weak diffraction peaks from elementary Bi accompanied by some unknown peaks were detected by XRD (not shown). TEM studies show agglomerates are main products. While reactions taken place at higher temperatures result in significant growth of wires. The ethylene diamine can coordinate with Bi3þ to form a triple-coordination compound. Thus, it is suggested that this is a typical coordinative reduction process in pure ethylene diamine system. In the high-pressure and alkalescent system, ethylene diamine mainly takes the role of electron transfer, displaying moderate intensity reductive characteristic [25]. Especially, the short distance between bismuth and nitrogen atom in the coordination compound is favorable for electron to transfer From N to Bi3þ , resulting in reduction of Bi3þ to Bi [26]. Meanwhile the elevated pressure applied provides a greater driving force for the reactions to occur [27,28]. It should be noted that no elementary Bi was detected by XRD when the
Y. Gao et al. / Chemical Physics Letters 367 (2003) 141–144
reaction was carried out in ethanol system containing zinc powder without ethylene diamine, which provide evidence that a coordinative reduction process might be involved. In addition, the chemical reaction between carbonyl and ethylene diamine in the above-mentioned system could increase electron cloud density around N atom, as a result enhances the ability of ethylene diamine to coordination with Bi3þ and reduction of Bi3þ [29]. Representative TEM images of Bi nanowires obtained from the synthesis at 160 °C for 6 h are presented in Figs. 2 and 3. About 20% portion of the samples shows wire-like structures. Other materials are small spherical particles with sizes less than 50 nm and large size agglomerates. Electron diffraction studies confirm that they are to be elementary Bi. This is agreement with XRD results in which no impurity phase was observed. The nanowires are, mainly straight with diameters of 20–30 nm and lengths of 0.2–2.5 lm, clearly observed in Fig. 2. It was found that the wires are uniform in width, while their lengths vary from several hundred nanometers to several micrometers. Fig. 2b shows a magnified image of an individual Bi nanowire. It is seen that the diameter of the nanowire is about 25 nm, and lengths reach up to 2:5 lm. Fig. 3b shows a representative high-
Fig. 2. TEM images and CBED pattern of Bi nanowires. (a) TEM microscopy at a low magnification; (b) individual Bi nanowire at a relatively higher magnification. Inset in (b) shows a CBED pattern of the individual nanowire. Note that the CBED pattern changes from regular into irregular, and finally into rings.
143
Fig. 3. (a) TEM image of the Bi nanowires. (b) A highresolution TEM image of one 10 nm diameter Bi nanowire that shows lattice fringes to be the (1 0 2) faces, (c) TEM image of the same Bi nanowires shown in (a) after electron beam radiation for ten seconds, holes generated from electron beam radiation can be clearly seen. Note the Bi nanowires have ever transformed into small liquid droplets and then evaporated or recrystallized.
resolution TEM (HRTEM) image of the nanowires, which confirms that the nanowires are single crystal with lattice fringes to be (1 0 2) direction. The convergent beam electron diffraction (CBED) pattern (inset of Fig. 2b) exhibits the diffraction spots characteristic of single-crystalline Bi, but it is also observed that the CBED pattern changes from regular into irregular, and finally to polycrystalline diffraction rings, displaying the sensitive characteristic of metal bismuth to electron beam radiation. This phenomenon is also observed in HRTEM experiments. Amorphousized phenomenon can be clearly observed during measuring high-resolution image (Fig. 3b). Fig. 3c shows a TEM image of the same Bi nanowires in Fig. 3a after electron beam radiation. It is observed that small liquid droplets appeared during electron radiation, the droplets would re-crystallize to Bi particles after the radiation process, which lead to a single-crystal nanowire transforming into a polycrystalline nanowire. It is the Bi nanowires sensitive to electron beam radiation that makes the measurement of intrinsic electron diffraction pattern of the as-prepared nanowire difficult. Nonetheless, HRTEM has distinctly demonstrated that the wire-like structures in the sample are singlecrystalline metallic Bi nanowires. Since ethylene diamine is bidentate coordinating agent, the long chains of triple-coordination poly-nucleus compound of Bi3þ could be easily formed in the system. The long chains could serve as template for
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materials formation, hence the formation of Bi nanowires might be related to the long chain structure of bismuth poly-nucleus coordination, saving as template for Bi atoms to nuclei and crystallization. Further work should be done to make the mechanism established firmly. 4. Conclusions In summary, the above studies show that singlecrystalline metallic Bi nanowires with rhombohedral phase structure can be synthesized by a low-temperature solvothermal process. The formation mechanism of Bi nanowires could be related to the formation of long chain bismuth poly-nucleus coordination compound. The rational low-temperature solvothermal synthetic strategy may be extended to fabricate other metal nanowires by choosing appropriate coordinating agents. Acknowledgements This work was supported by the Chinese National Natural Science Foundation (20125103). References [1] J.T. Hu, T.W. Odom, C.M. Lieber, Acc. Chem. Res. 32 (1999) 435. [2] W.K. Hsu, B.H. Chang, Y.Q. Zhu, W.Q. Han, M. Terrones, N. Grobert, A.K. Cheetham, H.W. Kroto, D.R. Walton, J. Am. Chem. Soc. 122 (2000) 10155. [3] S. Iijima, Nature 354 (1991) 56. [4] W.J. Liang, M. Bockrath, D. Bozovic, J.H. Hafner, M. Tinkham, H. Park, Nature 411 (2001) 665. [5] V.F. Puntes, K.M. Krishnan, A.P. Alivisatos, Science 291 (2001) 2115. [6] X.G. Peng, L. Manna, W.D. Yang, J. Wickham, E. Scher, A. Kadavanich, A.P. Alivisatos, Nature 404 (2000) 59.
[7] J.D. Holmes, K.P. Johnstin, R.C. Doty, B.A. Korgel, Science 287 (2000) 1471. [8] M.S. Gudiksen, C.M. Lieber, J. Am. Chem. Soc. 122 (2000) 8801. [9] Y. Lei, L.D. Zhang, J.C. Fan, Chem. Phys. Lett. 338 (2001) 231. [10] M.H. Huang, Y. Wu, H. Feick, N. Tran, E. Weber, P. Yang, Adv. Mater. 13 (2001) 113. [11] T.W. Odom, J.L. Huang, P. Kim, C.M. Lieber, J. Phys. Chem. B 104 (2000) 2794. [12] T. Thurn-Albrecht, J. Schotter, C.A. Kastle, N. Emley, T. Shibauchi, L. Krusin-Elbaum, K. Guarini, C.T. Black, M.T. Tuominen, T.P. Russell, Science 290 (2000) 2126. [13] X.F. Duan, Y. Huang, Y. Cui, J. Wang, C.M. Lieber, Nature 409 (2001) 6816. [14] Y. Cui, C.M. Lieber, Science 291 (2001) 5505. [15] Z.B. Zhang, J.Y. Ying, M.S. Dresselhaus, J. Mater. Res. 13 (1998) 1745. [16] D. Gekhtman, Z.B. Zhang, D. Adderton, M.S. Dresselhaus, G. Dresselhaus, Phys. Rev. Lett. 82 (1999) 3887. [17] L.D. Hicks, T.C. Harman, M.S. Dresselhaus, Appl. Phys. Lett. 63 (1993) 3230. [18] Z.B. Zhang, D. Gekhman, M.S. Dresselhaus, J.Y. Ying, Chem. Mater. 11 (1999) 1659. [19] Y.D. Li, J.W. Wang, Z. Deng, J. Am. Chem. Soc. 123 (2001) 9904. [20] Y.H. Tang, Y.F. Zhang, C.S. Lee, N. Wang, D.P. Yu, I. Bello, S.T. Lee, Mater. Res. Soc. Symp. Proc. 526 (1998) 73. [21] Y. Moriyoshi, Y. Shimizu, T. Watanabe, Thin Solid Films 390 (2001) 26. [22] R. Ma, Y. Bando, T. Sato, Chem. Phys. Lett. 337 (2001) 61. [23] Y. Bando, K. Ogawa, D. Golberg, Chem. Phys. Lett. 347 (2001) 349. [24] W.Q. Han, J. Cumings, X.S. Huang, K. Bradley, A. Zettl, Chem. Phys. Lett. 346 (2001) 368. [25] W. Huntress, M. Mosesman, D. Elleman, J. Chem. Phys. 54 (1970) 843. [26] A.B. Dai, in: Coordination Chemistry, Academic Press, Beijing, 1987, pp. 368–378. [27] P.R. Bonneau, R.F. Jarvis Jr., R.B. Kaner, Nature 349 (1991) 510. [28] C.H. Wallace, S.-H. Kim, G.A. Rose, L. Rao, J.R. Heath, M. Nicol, R.B. Kaner, Appl. Phys. Lett. 72 (1998) 596. [29] J.T. Wang, in: Organic Chemistry, Nankai University Press, 1993, pp. 335–347.
Preparation and characterization of single-crystalline bismuth nanowires by a low-temperature solvothermal process Yuanhao Gao 1, Helin Niu, Chuan Zeng, Qianwang Chen
*
Structure Research Laboratory, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, PR China Received 15 July 2002
Abstract Single-crystalline metallic bismuth nanowires have been successfully prepared by a solvothermal process at low temperatures, using aqueous bismuth nitrate ½BiðNO3 Þ3 5H2 O and ethylene diamine ðH2 NCH2 CH2 NH2 Þ as starting materials. Characterizations have been carried out by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The diameter of the nanowires is about 20–30 nm and lengths range from 0.2 to 2:5 lm. The reduction of bismuth ions (Bi3þ ) and formation mechanism of nanowire were discussed based on the characteristic of the reaction system employed. Ó 2002 Elsevier Science B.V. All rights reserved.
1. Introduction Over the past several years, one-dimensional nanostructures including nanotubes [1–4], nanorods [5,6] and nanowires [7–10], have received considerable attention from the scientific community. Much effort has been carried out on understanding the electronic [4,11], magnetic [12], and optical [13] properties of these nanostructures because they exhibit novel physical and chemical properties different from their bulk counterparts due to their reduced sizes and large surface-to*
Corresponding author. Fax: +86-551-3607292. E-mail address: [email protected] (Q. Chen). 1 Present address: Department of Chemistry, PingDingShan Teachers College, Henan, China, Visiting Scholar in the University of Science and Technology of China.
volume ratio [1]. These one-dimensional nanostructures are also promising candidates for realizing nanoscale electronic [14], optical [13], and mechanical [1] devices because they retain wire-like connectivity despite their nanoscale radial dimension. To date, most synthetic efforts have been directed toward carbon nanotubes [3,4], semiconductor [6–8], metallic [5], and binary oxide [9,10] nanotubes and nanowires. It is known that bismuth has small effective mass (0:001m0 ) and large mean-free path (0.4 mm at 4 K), which makes Bi nanowire become an interesting system for studying quantum confinement effects [15,16]. In addition, nanoscale bismuth materials have been recently suggested to be responsible for the enhancement of thermoelectric properties at room temperature [17,18]. However, owing to the relatively low-melting point of Bi (271.3 °C), the
0009-2614/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII: S 0 0 0 9 - 2 6 1 4 ( 0 2 ) 0 1 6 8 0 - 9
142
Y. Gao et al. / Chemical Physics Letters 367 (2003) 141–144
synthesis of Bi nanowires is much more difficult [19]. Most of the existing high-temperature approaches, such as laser ablation [20], plasma-arc [21], or chemical vapor-phase synthesis [22–24] are inappropriate for synthesis of Bi nanowires. Hence, the investigations of rational synthesis, physical properties, and applications of the Bi nanowires remain as challenges to materials scientists. Here we report the synthesis of singlecrystalline metallic bismuth nanowires by a lowtemperature solvothermal process, using aqueous bismuth nitrate ½BiðNO3 Þ3 5H2 O and ethylene diamine as starting materials.
2. Experimental For the present experiment, the solvothermal technique is used to prepare Bi nanowires. The whole system consists of aqueous bismuth nitrate BiðNO3 Þ3 5H2 O, ethylene diamine and acetone. Two grams analytically pure aqueous bismuth nitrate BiðNO3 Þ3 5H2 O and 5 ml acetone were put into 40 ml pure ethylene diamine at room temperature to form a mixture with insoluble precipitate. The mixture was stirred strongly for 10 min and transferred into a stainless steel autoclave with inner Teflon vessel (volume, 80 ml). The autoclave was closed tightly to perform solvothermal process for 6 h at 160 °C. After the process, the obtained black product was washed with alcohol and distilled water three times, respectively, dried in air at 50 °C for 0.5 h. The sample was examined by XRD using a 18KW advanced X-ray diffractometer with ). The nanostrucCu Ka radiation (k ¼ 1:54056 A ture of as-prepared products was studied by TEM at an accelerating voltage of 200 kV.
3. Results and discussion Fig. 1 shows XRD pattern of the product. Compared the d values (d ¼ 3:9449, 3.7294, 3.2758, 2.3647, 2.2696, 2.0291, 1.9706, 1.8661, ) with 1.6386, 1.5547, 1.4900, 1.4419, 1.3861 A those in standard JCPDS cards (JCPDS, 05-0519), the peaks can be well indexed with the reflections of (0 0 3), (0 1 1), (1 0 2), (0 1 4), (1 1 0), (1 0 5),
Fig. 1. A typical XRD pattern of the obtained product.
(1 1 3), (0 2 2), (2 0 4), (0 1 7), (1 1 6), (2 1 2), (1 0 8) of Bi rhombohedral phase [space group: R3m (166)]. Lattice constants calculated from the dif and c ¼ 11:848 A , fraction data are a ¼ 4:552 A which are compatible with the literature values , c ¼ 11:852 A ). This XRD pattern (a ¼ 4:546 A indicates that the reduction of Bi3þ to elemental Bi is complete under current synthetic condition, consequently, pure metal Bi products were obtained. It is found that no or poor crystallinity elementary Bi was obtained under conditions of lower temperatures and shorter reaction times. For example, when the reaction was carried out at 130°C for 6 h, very weak diffraction peaks from elementary Bi accompanied by some unknown peaks were detected by XRD (not shown). TEM studies show agglomerates are main products. While reactions taken place at higher temperatures result in significant growth of wires. The ethylene diamine can coordinate with Bi3þ to form a triple-coordination compound. Thus, it is suggested that this is a typical coordinative reduction process in pure ethylene diamine system. In the high-pressure and alkalescent system, ethylene diamine mainly takes the role of electron transfer, displaying moderate intensity reductive characteristic [25]. Especially, the short distance between bismuth and nitrogen atom in the coordination compound is favorable for electron to transfer From N to Bi3þ , resulting in reduction of Bi3þ to Bi [26]. Meanwhile the elevated pressure applied provides a greater driving force for the reactions to occur [27,28]. It should be noted that no elementary Bi was detected by XRD when the
Y. Gao et al. / Chemical Physics Letters 367 (2003) 141–144
reaction was carried out in ethanol system containing zinc powder without ethylene diamine, which provide evidence that a coordinative reduction process might be involved. In addition, the chemical reaction between carbonyl and ethylene diamine in the above-mentioned system could increase electron cloud density around N atom, as a result enhances the ability of ethylene diamine to coordination with Bi3þ and reduction of Bi3þ [29]. Representative TEM images of Bi nanowires obtained from the synthesis at 160 °C for 6 h are presented in Figs. 2 and 3. About 20% portion of the samples shows wire-like structures. Other materials are small spherical particles with sizes less than 50 nm and large size agglomerates. Electron diffraction studies confirm that they are to be elementary Bi. This is agreement with XRD results in which no impurity phase was observed. The nanowires are, mainly straight with diameters of 20–30 nm and lengths of 0.2–2.5 lm, clearly observed in Fig. 2. It was found that the wires are uniform in width, while their lengths vary from several hundred nanometers to several micrometers. Fig. 2b shows a magnified image of an individual Bi nanowire. It is seen that the diameter of the nanowire is about 25 nm, and lengths reach up to 2:5 lm. Fig. 3b shows a representative high-
Fig. 2. TEM images and CBED pattern of Bi nanowires. (a) TEM microscopy at a low magnification; (b) individual Bi nanowire at a relatively higher magnification. Inset in (b) shows a CBED pattern of the individual nanowire. Note that the CBED pattern changes from regular into irregular, and finally into rings.
143
Fig. 3. (a) TEM image of the Bi nanowires. (b) A highresolution TEM image of one 10 nm diameter Bi nanowire that shows lattice fringes to be the (1 0 2) faces, (c) TEM image of the same Bi nanowires shown in (a) after electron beam radiation for ten seconds, holes generated from electron beam radiation can be clearly seen. Note the Bi nanowires have ever transformed into small liquid droplets and then evaporated or recrystallized.
resolution TEM (HRTEM) image of the nanowires, which confirms that the nanowires are single crystal with lattice fringes to be (1 0 2) direction. The convergent beam electron diffraction (CBED) pattern (inset of Fig. 2b) exhibits the diffraction spots characteristic of single-crystalline Bi, but it is also observed that the CBED pattern changes from regular into irregular, and finally to polycrystalline diffraction rings, displaying the sensitive characteristic of metal bismuth to electron beam radiation. This phenomenon is also observed in HRTEM experiments. Amorphousized phenomenon can be clearly observed during measuring high-resolution image (Fig. 3b). Fig. 3c shows a TEM image of the same Bi nanowires in Fig. 3a after electron beam radiation. It is observed that small liquid droplets appeared during electron radiation, the droplets would re-crystallize to Bi particles after the radiation process, which lead to a single-crystal nanowire transforming into a polycrystalline nanowire. It is the Bi nanowires sensitive to electron beam radiation that makes the measurement of intrinsic electron diffraction pattern of the as-prepared nanowire difficult. Nonetheless, HRTEM has distinctly demonstrated that the wire-like structures in the sample are singlecrystalline metallic Bi nanowires. Since ethylene diamine is bidentate coordinating agent, the long chains of triple-coordination poly-nucleus compound of Bi3þ could be easily formed in the system. The long chains could serve as template for
144
Y. Gao et al. / Chemical Physics Letters 367 (2003) 141–144
materials formation, hence the formation of Bi nanowires might be related to the long chain structure of bismuth poly-nucleus coordination, saving as template for Bi atoms to nuclei and crystallization. Further work should be done to make the mechanism established firmly. 4. Conclusions In summary, the above studies show that singlecrystalline metallic Bi nanowires with rhombohedral phase structure can be synthesized by a low-temperature solvothermal process. The formation mechanism of Bi nanowires could be related to the formation of long chain bismuth poly-nucleus coordination compound. The rational low-temperature solvothermal synthetic strategy may be extended to fabricate other metal nanowires by choosing appropriate coordinating agents. Acknowledgements This work was supported by the Chinese National Natural Science Foundation (20125103). References [1] J.T. Hu, T.W. Odom, C.M. Lieber, Acc. Chem. Res. 32 (1999) 435. [2] W.K. Hsu, B.H. Chang, Y.Q. Zhu, W.Q. Han, M. Terrones, N. Grobert, A.K. Cheetham, H.W. Kroto, D.R. Walton, J. Am. Chem. Soc. 122 (2000) 10155. [3] S. Iijima, Nature 354 (1991) 56. [4] W.J. Liang, M. Bockrath, D. Bozovic, J.H. Hafner, M. Tinkham, H. Park, Nature 411 (2001) 665. [5] V.F. Puntes, K.M. Krishnan, A.P. Alivisatos, Science 291 (2001) 2115. [6] X.G. Peng, L. Manna, W.D. Yang, J. Wickham, E. Scher, A. Kadavanich, A.P. Alivisatos, Nature 404 (2000) 59.
[7] J.D. Holmes, K.P. Johnstin, R.C. Doty, B.A. Korgel, Science 287 (2000) 1471. [8] M.S. Gudiksen, C.M. Lieber, J. Am. Chem. Soc. 122 (2000) 8801. [9] Y. Lei, L.D. Zhang, J.C. Fan, Chem. Phys. Lett. 338 (2001) 231. [10] M.H. Huang, Y. Wu, H. Feick, N. Tran, E. Weber, P. Yang, Adv. Mater. 13 (2001) 113. [11] T.W. Odom, J.L. Huang, P. Kim, C.M. Lieber, J. Phys. Chem. B 104 (2000) 2794. [12] T. Thurn-Albrecht, J. Schotter, C.A. Kastle, N. Emley, T. Shibauchi, L. Krusin-Elbaum, K. Guarini, C.T. Black, M.T. Tuominen, T.P. Russell, Science 290 (2000) 2126. [13] X.F. Duan, Y. Huang, Y. Cui, J. Wang, C.M. Lieber, Nature 409 (2001) 6816. [14] Y. Cui, C.M. Lieber, Science 291 (2001) 5505. [15] Z.B. Zhang, J.Y. Ying, M.S. Dresselhaus, J. Mater. Res. 13 (1998) 1745. [16] D. Gekhtman, Z.B. Zhang, D. Adderton, M.S. Dresselhaus, G. Dresselhaus, Phys. Rev. Lett. 82 (1999) 3887. [17] L.D. Hicks, T.C. Harman, M.S. Dresselhaus, Appl. Phys. Lett. 63 (1993) 3230. [18] Z.B. Zhang, D. Gekhman, M.S. Dresselhaus, J.Y. Ying, Chem. Mater. 11 (1999) 1659. [19] Y.D. Li, J.W. Wang, Z. Deng, J. Am. Chem. Soc. 123 (2001) 9904. [20] Y.H. Tang, Y.F. Zhang, C.S. Lee, N. Wang, D.P. Yu, I. Bello, S.T. Lee, Mater. Res. Soc. Symp. Proc. 526 (1998) 73. [21] Y. Moriyoshi, Y. Shimizu, T. Watanabe, Thin Solid Films 390 (2001) 26. [22] R. Ma, Y. Bando, T. Sato, Chem. Phys. Lett. 337 (2001) 61. [23] Y. Bando, K. Ogawa, D. Golberg, Chem. Phys. Lett. 347 (2001) 349. [24] W.Q. Han, J. Cumings, X.S. Huang, K. Bradley, A. Zettl, Chem. Phys. Lett. 346 (2001) 368. [25] W. Huntress, M. Mosesman, D. Elleman, J. Chem. Phys. 54 (1970) 843. [26] A.B. Dai, in: Coordination Chemistry, Academic Press, Beijing, 1987, pp. 368–378. [27] P.R. Bonneau, R.F. Jarvis Jr., R.B. Kaner, Nature 349 (1991) 510. [28] C.H. Wallace, S.-H. Kim, G.A. Rose, L. Rao, J.R. Heath, M. Nicol, R.B. Kaner, Appl. Phys. Lett. 72 (1998) 596. [29] J.T. Wang, in: Organic Chemistry, Nankai University Press, 1993, pp. 335–347.