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polypyrrole composite nanowires
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Chinese Chemical Letters 22 (2011) 123–126 www.elsevier.com/locate/cclet
Coordinated organogel templated fabrication of silver/polypyrrole composite nanowires Bo Tian Li, Li Ming Tang *, Kai Chen, Yu Xia, Xin Jin Laboratory of Advanced Materials, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China Received 12 April 2010
Abstract A new method to fabricate metal/conducting polymer composite nanowires is presented by taking silver/polypyrrole composite nanowires as an example. A silver (I)-coordinated organogel as template was prepared firstly, and redox-polymerization of pyrrole took place on the gel fiber, giving product of silver/polypyrrole nanowires. The silver/polypyrrole nanowires were characterized by multiple techniques. This strategy could be carried out in one-step procedure at room temperature, and it proves the utility of coordinated organogels in template synthesis of polymer nanostructures. # 2010 Li Ming Tang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: Coordinated organogel; Template polymerization; Polypyrrole; Composite nanowires
In the past several years, coordinated organogels in which the solvents are trapped by networks of metal-organic nanostructures have been developed extremely rapidly. Metal ions and organic molecules are connected through coordination bonds to form one-dimensional fibers. The reversible nature of coordination bonds and the special catalytic and reactive characteristics of metal ions impart these gels great application potential in different areas, such as stimuli-responsive materials [1], biomedical materials [2], selective sorbents [3], and catalytic agents [4]. Moreover, the synthesis of nanostructures using metallogels as template is expected to possess some important properties because of the existence of metal ions [5]. Traditionally, organogel templated fabrications are limited to the synthesis of inorganic nanostructures [6]; some researchers have introduced coordinated gels into preparation of nanostructured polymers [7,8], however, in these cases the gels acted just as inverse template in monomeric solvents for producing porous polymers. The preparation of silver/polypyrrole (Ag/PPy) composites has been of increasing interest. Combining electrical characteristics of metal and conductive properties of polymers, these composites show enhanced electrocatalytic activity and increased conductivity [9,10], and present excellent potentials for different applications, such as sensors and electric devices [11,12]. Recently, our group has developed a silver coordinated organogel, based on which we managed to fabricate polymer nanotubes [13]. The silver ions in the gel fibers play an important role in the formation of core/shell structured fibers by attracting crosslinked polymer to adhere onto the surfaces of gel fibers. To make the silver ions more useful,
* Corresponding author. E-mail address: [email protected] (L.M. Tang). 1001-8417/$ – see front matter # 2010 Li Ming Tang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2010.06.034
[()TD$FIG] 124
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Scheme 1. Illustration of the procedure for fabrication of silver/PPy composite nanowires.
herein we focused on the oxidative reactivity of the silver ions in the gel fibers, to fabricate Ag/PPy composite nanowires. In this strategy, pyrrole is oxidized by the silver ions in the gel fibers while the coordinated organogel breaks up simultaneously. After the redox-polymerization, silver nanoparticles were found doping in the PPy wires, indicating that the composite nanowires were successfully prepared by this simple method. Although a variety of methods for fabricating Ag/PPy composites have been reported [14,15], only a few examples of Ag/PPy composites nanowires with regular shape have been achieved so far [16,17]. To our knowledge, this is the first time that Ag/PPy composite nanowires have been fabricated using coordinated organogels as template. The preparation is illustrated in Scheme 1. Tripodal ligand L (tripyridin-3-yl-benzene-1,3,5-tricarboxylate) was easily synthesized by our previous procedure [13] with the details shown in the supporting information, which could gelate various organic solvents with AgNO3 (at molar ratio of L/AgNO3 = 2/3). Pyrrole monomer was added to a THF solution of L, after injecting the THF solution of AgNO3 to L, a coordinated organogel was produced immediately. Successively, polymerization took place at room temperature for 2 weeks while the color of the gel turned black. After reaction, excessive ammonia was added into the gel to remove residue template gel and the product of Ag/PPy composite nanowires was obtained as dark powder. The fibrillar networks of the coordinated organogel (2 wt%) are observed by TEM. The average diameter of the nanofibers is 200 nm as shown in Fig. 1(a). Fig. 1(c) shows well-shaped Ag/PPy nanowires with their diameters of about 200–250 nm. The dark particles sheathed by an outer layer indicate the formation of Ag/PPy composites. In order to understand the process of template fabrication, the TEM image of the sample obtained in the middle stage of polymerization without ammonia treatment is observed in Fig. 1(b). As the template, the nano fibers of coordinated organogel (as indicated by arrow A) still exist, and their surface is covered by a layer of Ag/PPy composite formed in the early phase, which is indicated by arrow B in Fig. 1(b). The SEM image of the sample of Ag/PPy composite reveals a network structure in Fig. 1(d). Similar to the original gel fibers, the networks of Ag/PPy nanowires are branched and interconnected. A typical TEM image of a single nanowire is shown in Fig. 2, giving a better profile of the Ag/PPy composite. Energy dispersive spectroscopy (EDS) analysis of the selected region proves the existence of silver. The silver nanoparticles are dispersed throughout the PPy matrix, and they are almost spherical, with diameters of about 30– 60 nm. These results can be ascribed to the long-time redox-polymerization with a low reaction rate, which helps the formation of Ag/PPy composite with regular structure. The composition of the nanowires is investigated by X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). The XRD pattern of the product confirms the presence of elemental silver. The broad peak centered at 2u = 24.58 is ascribed to weak ordering parallel to the polymer chain. The sharp peaks at 2u = 38.38, 44.48 and 64.88 are clearly seen, corresponding to (1 1 1), (2 0 0), and (2 2 0) of silver crystal planes respectively [11]. These sharp peaks are absent in the XRD of pure polypyrrole, which was synthesized by rapid chemical oxidative
[()TD$FIG]
B.T. Li et al. / Chinese Chemical Letters 22 (2011) 123–126
125
Fig. 1. (a) TEM image of coordinated organogel; (b) TEM image of the sample obtained at the middle stage of polymerization (stored for one week); (c) and (d) are TEM and SEM images of Ag/PPy composite nanowires, respectively.
[()TD$FIG]
Fig. 2. EDS of selected area of Ag/PPy composite nanowire.
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B.T. Li et al. / Chinese Chemical Letters 22 (2011) 123–126
polymerization of pyrrole using ammonium persulfate as oxidant. The FT-IR spectrum of Ag/PPy nanowires shows the characteristic vibrations of doped PPy. The broad peak at 3410 cm 1 is assigned as the typical N–H stretching vibration, and the absorptions at 1652, 1577 and 1440 cm 1 are assigned as fundamental vibrations of pyrrole rings. Moreover, the bipolaron bands at 1195 and 918 cm 1 indicate the formation of PPy in its doped state [18]. The peak at 1380 cm 1 is attributed to the remnant NO3 anion due to the N–O stretch. The formation mechanism of Ag/PPy nanowires is speculated as reactive template polymerization, in which the fibers of silver coordinated gel act as reactive templates. Pyrrole monomers were oxidized into polypyrrole along the nanofibers by silver ions in the template, and meanwhile silver ions were reduced into silver nanoparticles, leading to the degradation of the template gel. In summary, we developed a simple approach to achieve Ag/PPy composite nanowires. This synthetic route is advantageous because it takes place through a one-step process at room temperature, and the product of Ag/PPy composite nanowires may find applications in electric devices as already mentioned in the literature [11,12]. Our study has also proved the utility of coordinated organogels in template synthesis of polymers. Using this strategy, a wide variety of metal/polymer nanowires or nanotubes could be prepared under appropriate conditions. Acknowledgments The financial support from the National Natural Science Foundation of China (Nos. 20574041 and 20874055) and Hi-tech Research and Development Program (863 plan) of China (No. SQ2009AA06XK1482459) is gratefully acknowledged. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/ j.cclet.2010.06.034. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18]
W.G. Weng, J.B. Beck, A.M. Jamieson, et al. J. Am. Chem. Soc. 128 (2006) 11663. S. Ray, A.K. Das, A. Banerjee, Chem. Mater. 19 (2007) 1633. B.G. Xing, M.F. Choi, B. Xu, Chem. Commun. 4 (2002) 362. B.G. Xing, M.F. Choi, B. Xu, Chem. Eur. J. 8 (2002) 5028. M. Llusar, C. Sanchez, Chem. Mater. 20 (2008) 782. J.H. Jung, Y. Ono, S. Shinkai, Angew. Chem. Int. Ed. 39 (2000) 1862. Q. Wei, S.L. James, Chem. Commun. 12 (2005) 1555. J.F. Yin, G.L. Yang, H.L. Wang, et al. Chem. Commun. (2007) 4614. N.A. Nikonorova, E.B. Barmatov, D.A. Pebalk, et al. J. Phys. Chem. C 111 (2007) 8451. A. Malinauskas, Synth. Meth. 107 (1999) 75. X.M. Feng, Z.Z. Sun, W.H. Hou, et al. Nanotechnology 18 (2007) 195603. H.T. Lee, Y.C. Liu, Polymer 46 (2005) 10727. K. Chen, L.M. Tang, Y. Xia, et al. Langmuir 24 (2008) 13838. P. Dallas, D. Niarchos, D. Vrbanic, et al. Polymer 48 (2007) 2007. J.M. Pringle, O. Winther-Jensen, C. Lynam, et al. Adv. Funct. Mater. 18 (2008) 2031. A.H. Chen, H.Q. Wang, X.Y. Li, Chem. Commun. 14 (2005) 1863. A.H. Chen, H.X. Xie, H.Q. Wang, et al. Synth. Meth. 156 (2006) 346. B. Tian, G. Zerbi, J. Chem. Phys. 92 (1990) 3892.
Chinese Chemical Letters 22 (2011) 123–126 www.elsevier.com/locate/cclet
Coordinated organogel templated fabrication of silver/polypyrrole composite nanowires Bo Tian Li, Li Ming Tang *, Kai Chen, Yu Xia, Xin Jin Laboratory of Advanced Materials, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China Received 12 April 2010
Abstract A new method to fabricate metal/conducting polymer composite nanowires is presented by taking silver/polypyrrole composite nanowires as an example. A silver (I)-coordinated organogel as template was prepared firstly, and redox-polymerization of pyrrole took place on the gel fiber, giving product of silver/polypyrrole nanowires. The silver/polypyrrole nanowires were characterized by multiple techniques. This strategy could be carried out in one-step procedure at room temperature, and it proves the utility of coordinated organogels in template synthesis of polymer nanostructures. # 2010 Li Ming Tang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: Coordinated organogel; Template polymerization; Polypyrrole; Composite nanowires
In the past several years, coordinated organogels in which the solvents are trapped by networks of metal-organic nanostructures have been developed extremely rapidly. Metal ions and organic molecules are connected through coordination bonds to form one-dimensional fibers. The reversible nature of coordination bonds and the special catalytic and reactive characteristics of metal ions impart these gels great application potential in different areas, such as stimuli-responsive materials [1], biomedical materials [2], selective sorbents [3], and catalytic agents [4]. Moreover, the synthesis of nanostructures using metallogels as template is expected to possess some important properties because of the existence of metal ions [5]. Traditionally, organogel templated fabrications are limited to the synthesis of inorganic nanostructures [6]; some researchers have introduced coordinated gels into preparation of nanostructured polymers [7,8], however, in these cases the gels acted just as inverse template in monomeric solvents for producing porous polymers. The preparation of silver/polypyrrole (Ag/PPy) composites has been of increasing interest. Combining electrical characteristics of metal and conductive properties of polymers, these composites show enhanced electrocatalytic activity and increased conductivity [9,10], and present excellent potentials for different applications, such as sensors and electric devices [11,12]. Recently, our group has developed a silver coordinated organogel, based on which we managed to fabricate polymer nanotubes [13]. The silver ions in the gel fibers play an important role in the formation of core/shell structured fibers by attracting crosslinked polymer to adhere onto the surfaces of gel fibers. To make the silver ions more useful,
* Corresponding author. E-mail address: [email protected] (L.M. Tang). 1001-8417/$ – see front matter # 2010 Li Ming Tang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2010.06.034
[()TD$FIG] 124
B.T. Li et al. / Chinese Chemical Letters 22 (2011) 123–126
Scheme 1. Illustration of the procedure for fabrication of silver/PPy composite nanowires.
herein we focused on the oxidative reactivity of the silver ions in the gel fibers, to fabricate Ag/PPy composite nanowires. In this strategy, pyrrole is oxidized by the silver ions in the gel fibers while the coordinated organogel breaks up simultaneously. After the redox-polymerization, silver nanoparticles were found doping in the PPy wires, indicating that the composite nanowires were successfully prepared by this simple method. Although a variety of methods for fabricating Ag/PPy composites have been reported [14,15], only a few examples of Ag/PPy composites nanowires with regular shape have been achieved so far [16,17]. To our knowledge, this is the first time that Ag/PPy composite nanowires have been fabricated using coordinated organogels as template. The preparation is illustrated in Scheme 1. Tripodal ligand L (tripyridin-3-yl-benzene-1,3,5-tricarboxylate) was easily synthesized by our previous procedure [13] with the details shown in the supporting information, which could gelate various organic solvents with AgNO3 (at molar ratio of L/AgNO3 = 2/3). Pyrrole monomer was added to a THF solution of L, after injecting the THF solution of AgNO3 to L, a coordinated organogel was produced immediately. Successively, polymerization took place at room temperature for 2 weeks while the color of the gel turned black. After reaction, excessive ammonia was added into the gel to remove residue template gel and the product of Ag/PPy composite nanowires was obtained as dark powder. The fibrillar networks of the coordinated organogel (2 wt%) are observed by TEM. The average diameter of the nanofibers is 200 nm as shown in Fig. 1(a). Fig. 1(c) shows well-shaped Ag/PPy nanowires with their diameters of about 200–250 nm. The dark particles sheathed by an outer layer indicate the formation of Ag/PPy composites. In order to understand the process of template fabrication, the TEM image of the sample obtained in the middle stage of polymerization without ammonia treatment is observed in Fig. 1(b). As the template, the nano fibers of coordinated organogel (as indicated by arrow A) still exist, and their surface is covered by a layer of Ag/PPy composite formed in the early phase, which is indicated by arrow B in Fig. 1(b). The SEM image of the sample of Ag/PPy composite reveals a network structure in Fig. 1(d). Similar to the original gel fibers, the networks of Ag/PPy nanowires are branched and interconnected. A typical TEM image of a single nanowire is shown in Fig. 2, giving a better profile of the Ag/PPy composite. Energy dispersive spectroscopy (EDS) analysis of the selected region proves the existence of silver. The silver nanoparticles are dispersed throughout the PPy matrix, and they are almost spherical, with diameters of about 30– 60 nm. These results can be ascribed to the long-time redox-polymerization with a low reaction rate, which helps the formation of Ag/PPy composite with regular structure. The composition of the nanowires is investigated by X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). The XRD pattern of the product confirms the presence of elemental silver. The broad peak centered at 2u = 24.58 is ascribed to weak ordering parallel to the polymer chain. The sharp peaks at 2u = 38.38, 44.48 and 64.88 are clearly seen, corresponding to (1 1 1), (2 0 0), and (2 2 0) of silver crystal planes respectively [11]. These sharp peaks are absent in the XRD of pure polypyrrole, which was synthesized by rapid chemical oxidative
[()TD$FIG]
B.T. Li et al. / Chinese Chemical Letters 22 (2011) 123–126
125
Fig. 1. (a) TEM image of coordinated organogel; (b) TEM image of the sample obtained at the middle stage of polymerization (stored for one week); (c) and (d) are TEM and SEM images of Ag/PPy composite nanowires, respectively.
[()TD$FIG]
Fig. 2. EDS of selected area of Ag/PPy composite nanowire.
126
B.T. Li et al. / Chinese Chemical Letters 22 (2011) 123–126
polymerization of pyrrole using ammonium persulfate as oxidant. The FT-IR spectrum of Ag/PPy nanowires shows the characteristic vibrations of doped PPy. The broad peak at 3410 cm 1 is assigned as the typical N–H stretching vibration, and the absorptions at 1652, 1577 and 1440 cm 1 are assigned as fundamental vibrations of pyrrole rings. Moreover, the bipolaron bands at 1195 and 918 cm 1 indicate the formation of PPy in its doped state [18]. The peak at 1380 cm 1 is attributed to the remnant NO3 anion due to the N–O stretch. The formation mechanism of Ag/PPy nanowires is speculated as reactive template polymerization, in which the fibers of silver coordinated gel act as reactive templates. Pyrrole monomers were oxidized into polypyrrole along the nanofibers by silver ions in the template, and meanwhile silver ions were reduced into silver nanoparticles, leading to the degradation of the template gel. In summary, we developed a simple approach to achieve Ag/PPy composite nanowires. This synthetic route is advantageous because it takes place through a one-step process at room temperature, and the product of Ag/PPy composite nanowires may find applications in electric devices as already mentioned in the literature [11,12]. Our study has also proved the utility of coordinated organogels in template synthesis of polymers. Using this strategy, a wide variety of metal/polymer nanowires or nanotubes could be prepared under appropriate conditions. Acknowledgments The financial support from the National Natural Science Foundation of China (Nos. 20574041 and 20874055) and Hi-tech Research and Development Program (863 plan) of China (No. SQ2009AA06XK1482459) is gratefully acknowledged. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/ j.cclet.2010.06.034. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18]
W.G. Weng, J.B. Beck, A.M. Jamieson, et al. J. Am. Chem. Soc. 128 (2006) 11663. S. Ray, A.K. Das, A. Banerjee, Chem. Mater. 19 (2007) 1633. B.G. Xing, M.F. Choi, B. Xu, Chem. Commun. 4 (2002) 362. B.G. Xing, M.F. Choi, B. Xu, Chem. Eur. J. 8 (2002) 5028. M. Llusar, C. Sanchez, Chem. Mater. 20 (2008) 782. J.H. Jung, Y. Ono, S. Shinkai, Angew. Chem. Int. Ed. 39 (2000) 1862. Q. Wei, S.L. James, Chem. Commun. 12 (2005) 1555. J.F. Yin, G.L. Yang, H.L. Wang, et al. Chem. Commun. (2007) 4614. N.A. Nikonorova, E.B. Barmatov, D.A. Pebalk, et al. J. Phys. Chem. C 111 (2007) 8451. A. Malinauskas, Synth. Meth. 107 (1999) 75. X.M. Feng, Z.Z. Sun, W.H. Hou, et al. Nanotechnology 18 (2007) 195603. H.T. Lee, Y.C. Liu, Polymer 46 (2005) 10727. K. Chen, L.M. Tang, Y. Xia, et al. Langmuir 24 (2008) 13838. P. Dallas, D. Niarchos, D. Vrbanic, et al. Polymer 48 (2007) 2007. J.M. Pringle, O. Winther-Jensen, C. Lynam, et al. Adv. Funct. Mater. 18 (2008) 2031. A.H. Chen, H.Q. Wang, X.Y. Li, Chem. Commun. 14 (2005) 1863. A.H. Chen, H.X. Xie, H.Q. Wang, et al. Synth. Meth. 156 (2006) 346. B. Tian, G. Zerbi, J. Chem. Phys. 92 (1990) 3892.