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Synthesis of size-tunable metal nanoparticles based on polyacrylonitrile nanofibers enabled by electrospinning and microwave irradiation
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Materials Letters 62 (2008) 692 – 694 www.elsevier.com/locate/matlet
Synthesis of size-tunable metal nanoparticles based on polyacrylonitrile nanofibers enabled by electrospinning and microwave irradiation Jingyu Chen, Zhenyu Li, Danming Chao, Wanjin Zhang, Ce Wang ⁎ Alan G. MacDiarmid Institute, Jilin University, Changchun 130012, PR China Received 25 February 2007; accepted 18 June 2007 Available online 23 June 2007
Abstract In this study, a simple route has been presented for the preparation of size-tunable metal (Pd, Ag) nanoparticles (NPs) based on polyacrylonitrile (PAN) nanofibers through electrospinning and microwave irradiation. PAN nanofibers containing metal salts (PdCl2 and AgNO3) were prepared through electrospinning and then the salts were reduced to metal NPs under microwave irradiation. The diameters of the metal NPs can be controlled by varying the molar ratio of PdCl2 to PAN and the concentration of NaOH. The structures and distribution of the metal nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). © 2007 Elsevier B.V. All rights reserved. Keywords: Nanocomposites; Polymers; Electrospinning; Microwave irradiation; Metal
1. Introduction Nano-scale metal particles are of great research interest due to their unique quantum effect [1,2] and potential applications in optoelectronic devices [3], ultra-sensitive chemical and biological sensors [4,5], and chemical and photochemical reactions [6–8]. Recently, for practical applications such as heterogeneous catalysis and surface enhanced Raman scattering (SERS), fabrication of metal nanoparticles (NPs) based on solid substrates has attracted special interest [9–15]. Many methods have been developed to prepare metal NPs based on solid substrates, such as electro/electroless deposition [9,10], linkage with biomolecules [11], physical evaporation [12], UV irradiation [13], chemical reducing [14], pyrogenation [15], etc. Nanofibers fabricated via electrospinning have gained special attraction for their multifunctional properties in biomedical fields, catalyst supports, sensors, and sacrificial templates [16]. Taking the advantage of high surface-area-to-volume ratio of electrospun nanofibers, much focus has been put on the fabrication of functional NPs on electrospun nanofibers. For example, Hou and
Reneker fabricated Fe NPs based on carbon nanofibers [17]. Dong et al. reported the assembly of metal NPs on electrospun poly (4-vinylpyridine) fibers [18]. Our group fabricated Ag, (Ag2S) NPs and Cu2S nanorods based on PAN nanofibers [19]. Wang and co-workers assembled metal oxide NPs on electrospun nanofibers [20]. However, to the best of our knowledge, little attention has been put on the fabrication of metal NPs based on electrospun nanofibers via microwave irradiation. In this communication, microwave irradiation [21–24] and electrospinning were combined for the first time to fabricate metal NPs with diameter of several nanometers on electrospun polymer nanofibers. In our experiment, microwave irradiation is used to rapidly prepare metal NPs in polymer nanofibers matrices in ethylene glycol. The time of this process is less than half a minute, which is especially advantageous for large quantity synthesis in industry. We believe that our method can offer a powerful platform to design and fabricate functional polymer/metal nanocomposite fibers with desirable properties. 2. Experimental 2.1. Preparation of PAN/metal salt–DMF solution
⁎ Corresponding author. Tel.: +86 431 85168292; fax: +86 431 85168292. E-mail address: [email protected] (C. Wang). 0167-577X/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2007.06.047
1.4 g of PAN (MW: 60,000 and 150,000, purchased from Jilin Chem. Co) and 0.02 g of AOT (Dioctyl sulfosuccinate
J. Chen et al. / Materials Letters 62 (2008) 692–694
693
cooled down to room temperature and magnetically stirred for 12 h. Finally, a suitable metallic salt (PdCl2 or AgNO3) was added to the solution under magnetic stirring for 12 h in a dark room. 2.2. Electrospinning Electrospinning was conducted by putting the solution in a glass syringe with tip inner diameter of 1 mm. The distance from the tip of the spinning nozzle to the Al collector was adjusted to 20 cm. To prevent the reduction of the metallic ions inside the syringe, a piece of Al foil instead of a copper wire was used as anode. 2.3. Microwave irradiation The electrospun nanofiber mat peeled from the Al foil was immersed in 5 ml ethylene glycol containing certain amount of NaOH. The container was heated in the center of a Haier domestic 2450 MHz microwave oven for 25 s. 2.4. Measurements Transmission electron microscopy (TEM) and selective area electron diffraction (SAED) were carried out on a Hitachi H8100 electron microscope with an acceleration voltage of 200 kV. Scanning electron microscopy (SEM) measurements were performed on a SHIMADZU SSX-550 microscope. X-ray diffraction patterns (XRD) were obtained with a Siemens D5005 diffractometer using Cu Kα radiation. 3. Results and discussion
Fig. 1. (a) TEM image of the PAN/Pd nanocomposite fibers by keeping the molar ratio of PAN:Pd at 20:1. (b) TEM image of the PAN/Pd nanocomposite fibers by keeping the molar ratio of PAN:Pd at 40:1. (c) The XRD pattern of the PAN/Pd nanocomposite fibers (⁎ diffraction peaks from glass). The molecular weight of PAN is 60,000 and the concentration of PAN and NaOH is 7 wt.% and 0.2 M, respectively. The insert in (A) is SAED pattern of Pd nanoparticles.
sodium: C20H37O7SNa, purchased from Aldrich) were dissolved in 18.6 g of DMF followed by heating the solution at 90 °C for 6 h under magnetic stirring. Then, the solution was
Pd NPs on PAN nanofibers have been prepared firstly and characterized by TEM. Fig. 1a shows the TEM image of the products reduced in ethylene glycol containing 0.2 M NaOH (the molar ratio of PAN:Pd is 20:1 and Mw of PAN is 60,000). In the image it can be observed that Pd NPs with average diameter of 10 nm were obtained on PAN nanofibers. The diameter of Pd nanoparticles can be controlled by the variation of Pd salt content in PAN nanofibers. With other conditions fixed, when the molar ratio of PAN to Pd is increased to 40:1, Pd NPs with diameter less than 5 nm can be obtained (Fig. 1b). Compared with the products in Fig 1a and b, at lower salt content, the Pd NPs tend to distribute better on PAN nanofibers. The insert in Fig. 1a shows the selective area electron diffraction (SAED) pattern of these Pd NPs, proving these Pd NPs are polycrystalline and in the standard face-centered nanocrystals [25]. Additionally, these facecentered Pd NPs have been further proved by XRD. In XRD pattern (Fig. 1c), three typical and broadening peaks at 2θ = 40, 46.5 and 68 can be clearly detected, which correspond to the face-centered Pd (111, 200, and 220). A sharp crystalline peak at 17° corresponding to the orthorhombic PAN (110) reflection is also detected. In our experiment, the sizes of Pd NPs can be also adjusted by changing the concentration of NaOH (keeping the molar ratio of PAN: Pd at 40:1). When the [NaOH] is 0 M, aggregated Pd NPs with the diameter more than 30 nm can be clearly detected (Fig. 2a). As the [NaOH] is 0.01 M, Pd NPs with average diameter of 7 nm on PAN nanofibers have been obtained and the aggregation of Pd NPs greatly reduced (Fig. 2b). These results can be explained that under the
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J. Chen et al. / Materials Letters 62 (2008) 692–694
Fig. 2. TEM images of the PAN/Pd nanocomposite fibers by keeping the molar ratio of PAN:Pd at 40:1. The concentration of NaOH is 0 M (a) and 0.01 M (b), respectively.
Acknowledgements This work has been supported in part by the National Natural Science Foundation of China (NSFC No. 50473008 and 50673034) and in part by HEADWATERS NANOKINETIX. INC. References [1] [2] [3] [4] [5] Fig. 3. TEM image of PAN/Ag nanocomposite fibers. The inset is SAED pattern of Ag nanoparticles.
[6] [7] [8] [9]
microwave irradiation, NaOH can hasten the reduction and can reduce the size of Pd NPs [26]. Our method can also be applied to fabricate Ag NPs on PAN nanofibers according to the same steps mentioned above (PAN: 150,000; [NaOH]: 0.01 M; and PAN:Ag is 20:1). The product was also characterized with TEM and shown in Fig. 3. From the TEM image, it can be found that Ag NPs with diameter of 7–15 nm were fabricated on PAN nanofibers. The insert of Fig. 3 is SAED pattern of the Ag nanoparticles, confirming these Ag nanoparticles exist in the standard face-centered cubic.
4. Conclusion In this communication, we have demonstrated a simple route for the preparation of size-controlled metal NPs/PAN nanocomposite fibers. Comparing with the previous methods, the size of the metal NPs can be adjusted by varying the molar ratio of PdCl2 to PAN and the concentration of NaOH. We believe that our method should be versatile and effective for designing and fabricating metal/polymer nano-hybrids with desirable properties.
[10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26]
A.P. Alivisatos, Science 271 (1996) 993. L.N. Lewis, Chem. Rev. 93 (1993) 2693. V.L. Colvin, M.C. Schlamp, A.P. Alivisatos, Nature 370 (1994) 354. W.C. Chan, S. Nie, Science 281 (1998) 2016. M. Bruchez Jr., M. Moronne, P. Gin, S. Weiss, A.P. Alivisatos, Science 281 (1998) 2013. D.L. Feldheim Jr., C.A. Foss, Metal Nanoparticles, Marcel Dekker, New York, 2002. D. Astruc, F. Lu, J.R. Aranzaes, Angew. Chem., Int. Ed. Engl. 44 (2005) 7852. A. Roucoux, J. Schulz, H. Patin, Chem. Rev. 102 (2002) 3757. T.M. Day, P.R. Unwin, N.R. Wilson, J.V. Macpherson, J. Am. Chem. Soc. 127 (2005) 10639. L. Qu, L. Dai, J. Am. Chem. Soc. 127 (2005) 10806. M.J. Moghaddam, S. Taylor, M. Gao, S. Huang, L. Dai, M.J. McCall, Nano Lett. 4 (2004) 89. A. Bezryadin, C.N. Lau, M. Tinkham, Nature 404 (2000) 971. Z.Y. Li, H.M. Huang, T.C. Shang, F. Yang, W. Zheng, C. Wang, Nanotechnology 17 (2006) 917. M.M. Demir, M.A. Gulgun, Y.Z. Menceloglu, B. Erman, S.S. Abramchuk, E.E. Makhaeva, Macromolecules 37 (2004) 1787. Z.Y. Li, H.M. Huang, C. Wang, Solid State Phenom. 121 (2007) 123. D. Li, Y. Xia, Adv. Mater. 16 (2004) 1151. H. Hou, D.H. Reneker, Adv. Mater. 16 (2004) 69. H. Dong, E. Fey, A. Gandelman, W.E. Jones Jr., Chem. Mater. 18 (2006) 2008. F. Dong, Z. Li, H. Huang, F. Yang, W. Zheng, C. Wang, Mater. Lett. 61 (2007) 6556. C. Drew, X. Liu, D. Ziegler, X. Wang, F.F. Bruno, J. Whitten, Nano Lett. 3 (2003) 143. R.A. Abramovitch, Org. Prep. Proced. Int. 23 (1991) 683. J.R.J. Paré, J.M.R. Belanger, S.S. Stafford, Trends Anal. Chem. 13 (1994) 176. W.Y. Yu, W.X. Tu, H.F. Liu, Langmuir 15 (1999) 6. W.X. Tu, H.F. Liu, Chem. Mater. 12 (2000) 564. D. Bera, S.C. Kuiry, M. McCutchen, S. Seal, H. Heinrich, J. Appl. Phys. 96 (2004) 5153. W.X. Tu, H.F. Liu, J. Mater. Chem. 10 (2000) 2207.
Materials Letters 62 (2008) 692 – 694 www.elsevier.com/locate/matlet
Synthesis of size-tunable metal nanoparticles based on polyacrylonitrile nanofibers enabled by electrospinning and microwave irradiation Jingyu Chen, Zhenyu Li, Danming Chao, Wanjin Zhang, Ce Wang ⁎ Alan G. MacDiarmid Institute, Jilin University, Changchun 130012, PR China Received 25 February 2007; accepted 18 June 2007 Available online 23 June 2007
Abstract In this study, a simple route has been presented for the preparation of size-tunable metal (Pd, Ag) nanoparticles (NPs) based on polyacrylonitrile (PAN) nanofibers through electrospinning and microwave irradiation. PAN nanofibers containing metal salts (PdCl2 and AgNO3) were prepared through electrospinning and then the salts were reduced to metal NPs under microwave irradiation. The diameters of the metal NPs can be controlled by varying the molar ratio of PdCl2 to PAN and the concentration of NaOH. The structures and distribution of the metal nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). © 2007 Elsevier B.V. All rights reserved. Keywords: Nanocomposites; Polymers; Electrospinning; Microwave irradiation; Metal
1. Introduction Nano-scale metal particles are of great research interest due to their unique quantum effect [1,2] and potential applications in optoelectronic devices [3], ultra-sensitive chemical and biological sensors [4,5], and chemical and photochemical reactions [6–8]. Recently, for practical applications such as heterogeneous catalysis and surface enhanced Raman scattering (SERS), fabrication of metal nanoparticles (NPs) based on solid substrates has attracted special interest [9–15]. Many methods have been developed to prepare metal NPs based on solid substrates, such as electro/electroless deposition [9,10], linkage with biomolecules [11], physical evaporation [12], UV irradiation [13], chemical reducing [14], pyrogenation [15], etc. Nanofibers fabricated via electrospinning have gained special attraction for their multifunctional properties in biomedical fields, catalyst supports, sensors, and sacrificial templates [16]. Taking the advantage of high surface-area-to-volume ratio of electrospun nanofibers, much focus has been put on the fabrication of functional NPs on electrospun nanofibers. For example, Hou and
Reneker fabricated Fe NPs based on carbon nanofibers [17]. Dong et al. reported the assembly of metal NPs on electrospun poly (4-vinylpyridine) fibers [18]. Our group fabricated Ag, (Ag2S) NPs and Cu2S nanorods based on PAN nanofibers [19]. Wang and co-workers assembled metal oxide NPs on electrospun nanofibers [20]. However, to the best of our knowledge, little attention has been put on the fabrication of metal NPs based on electrospun nanofibers via microwave irradiation. In this communication, microwave irradiation [21–24] and electrospinning were combined for the first time to fabricate metal NPs with diameter of several nanometers on electrospun polymer nanofibers. In our experiment, microwave irradiation is used to rapidly prepare metal NPs in polymer nanofibers matrices in ethylene glycol. The time of this process is less than half a minute, which is especially advantageous for large quantity synthesis in industry. We believe that our method can offer a powerful platform to design and fabricate functional polymer/metal nanocomposite fibers with desirable properties. 2. Experimental 2.1. Preparation of PAN/metal salt–DMF solution
⁎ Corresponding author. Tel.: +86 431 85168292; fax: +86 431 85168292. E-mail address: [email protected] (C. Wang). 0167-577X/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2007.06.047
1.4 g of PAN (MW: 60,000 and 150,000, purchased from Jilin Chem. Co) and 0.02 g of AOT (Dioctyl sulfosuccinate
J. Chen et al. / Materials Letters 62 (2008) 692–694
693
cooled down to room temperature and magnetically stirred for 12 h. Finally, a suitable metallic salt (PdCl2 or AgNO3) was added to the solution under magnetic stirring for 12 h in a dark room. 2.2. Electrospinning Electrospinning was conducted by putting the solution in a glass syringe with tip inner diameter of 1 mm. The distance from the tip of the spinning nozzle to the Al collector was adjusted to 20 cm. To prevent the reduction of the metallic ions inside the syringe, a piece of Al foil instead of a copper wire was used as anode. 2.3. Microwave irradiation The electrospun nanofiber mat peeled from the Al foil was immersed in 5 ml ethylene glycol containing certain amount of NaOH. The container was heated in the center of a Haier domestic 2450 MHz microwave oven for 25 s. 2.4. Measurements Transmission electron microscopy (TEM) and selective area electron diffraction (SAED) were carried out on a Hitachi H8100 electron microscope with an acceleration voltage of 200 kV. Scanning electron microscopy (SEM) measurements were performed on a SHIMADZU SSX-550 microscope. X-ray diffraction patterns (XRD) were obtained with a Siemens D5005 diffractometer using Cu Kα radiation. 3. Results and discussion
Fig. 1. (a) TEM image of the PAN/Pd nanocomposite fibers by keeping the molar ratio of PAN:Pd at 20:1. (b) TEM image of the PAN/Pd nanocomposite fibers by keeping the molar ratio of PAN:Pd at 40:1. (c) The XRD pattern of the PAN/Pd nanocomposite fibers (⁎ diffraction peaks from glass). The molecular weight of PAN is 60,000 and the concentration of PAN and NaOH is 7 wt.% and 0.2 M, respectively. The insert in (A) is SAED pattern of Pd nanoparticles.
sodium: C20H37O7SNa, purchased from Aldrich) were dissolved in 18.6 g of DMF followed by heating the solution at 90 °C for 6 h under magnetic stirring. Then, the solution was
Pd NPs on PAN nanofibers have been prepared firstly and characterized by TEM. Fig. 1a shows the TEM image of the products reduced in ethylene glycol containing 0.2 M NaOH (the molar ratio of PAN:Pd is 20:1 and Mw of PAN is 60,000). In the image it can be observed that Pd NPs with average diameter of 10 nm were obtained on PAN nanofibers. The diameter of Pd nanoparticles can be controlled by the variation of Pd salt content in PAN nanofibers. With other conditions fixed, when the molar ratio of PAN to Pd is increased to 40:1, Pd NPs with diameter less than 5 nm can be obtained (Fig. 1b). Compared with the products in Fig 1a and b, at lower salt content, the Pd NPs tend to distribute better on PAN nanofibers. The insert in Fig. 1a shows the selective area electron diffraction (SAED) pattern of these Pd NPs, proving these Pd NPs are polycrystalline and in the standard face-centered nanocrystals [25]. Additionally, these facecentered Pd NPs have been further proved by XRD. In XRD pattern (Fig. 1c), three typical and broadening peaks at 2θ = 40, 46.5 and 68 can be clearly detected, which correspond to the face-centered Pd (111, 200, and 220). A sharp crystalline peak at 17° corresponding to the orthorhombic PAN (110) reflection is also detected. In our experiment, the sizes of Pd NPs can be also adjusted by changing the concentration of NaOH (keeping the molar ratio of PAN: Pd at 40:1). When the [NaOH] is 0 M, aggregated Pd NPs with the diameter more than 30 nm can be clearly detected (Fig. 2a). As the [NaOH] is 0.01 M, Pd NPs with average diameter of 7 nm on PAN nanofibers have been obtained and the aggregation of Pd NPs greatly reduced (Fig. 2b). These results can be explained that under the
694
J. Chen et al. / Materials Letters 62 (2008) 692–694
Fig. 2. TEM images of the PAN/Pd nanocomposite fibers by keeping the molar ratio of PAN:Pd at 40:1. The concentration of NaOH is 0 M (a) and 0.01 M (b), respectively.
Acknowledgements This work has been supported in part by the National Natural Science Foundation of China (NSFC No. 50473008 and 50673034) and in part by HEADWATERS NANOKINETIX. INC. References [1] [2] [3] [4] [5] Fig. 3. TEM image of PAN/Ag nanocomposite fibers. The inset is SAED pattern of Ag nanoparticles.
[6] [7] [8] [9]
microwave irradiation, NaOH can hasten the reduction and can reduce the size of Pd NPs [26]. Our method can also be applied to fabricate Ag NPs on PAN nanofibers according to the same steps mentioned above (PAN: 150,000; [NaOH]: 0.01 M; and PAN:Ag is 20:1). The product was also characterized with TEM and shown in Fig. 3. From the TEM image, it can be found that Ag NPs with diameter of 7–15 nm were fabricated on PAN nanofibers. The insert of Fig. 3 is SAED pattern of the Ag nanoparticles, confirming these Ag nanoparticles exist in the standard face-centered cubic.
4. Conclusion In this communication, we have demonstrated a simple route for the preparation of size-controlled metal NPs/PAN nanocomposite fibers. Comparing with the previous methods, the size of the metal NPs can be adjusted by varying the molar ratio of PdCl2 to PAN and the concentration of NaOH. We believe that our method should be versatile and effective for designing and fabricating metal/polymer nano-hybrids with desirable properties.
[10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26]
A.P. Alivisatos, Science 271 (1996) 993. L.N. Lewis, Chem. Rev. 93 (1993) 2693. V.L. Colvin, M.C. Schlamp, A.P. Alivisatos, Nature 370 (1994) 354. W.C. Chan, S. Nie, Science 281 (1998) 2016. M. Bruchez Jr., M. Moronne, P. Gin, S. Weiss, A.P. Alivisatos, Science 281 (1998) 2013. D.L. Feldheim Jr., C.A. Foss, Metal Nanoparticles, Marcel Dekker, New York, 2002. D. Astruc, F. Lu, J.R. Aranzaes, Angew. Chem., Int. Ed. Engl. 44 (2005) 7852. A. Roucoux, J. Schulz, H. Patin, Chem. Rev. 102 (2002) 3757. T.M. Day, P.R. Unwin, N.R. Wilson, J.V. Macpherson, J. Am. Chem. Soc. 127 (2005) 10639. L. Qu, L. Dai, J. Am. Chem. Soc. 127 (2005) 10806. M.J. Moghaddam, S. Taylor, M. Gao, S. Huang, L. Dai, M.J. McCall, Nano Lett. 4 (2004) 89. A. Bezryadin, C.N. Lau, M. Tinkham, Nature 404 (2000) 971. Z.Y. Li, H.M. Huang, T.C. Shang, F. Yang, W. Zheng, C. Wang, Nanotechnology 17 (2006) 917. M.M. Demir, M.A. Gulgun, Y.Z. Menceloglu, B. Erman, S.S. Abramchuk, E.E. Makhaeva, Macromolecules 37 (2004) 1787. Z.Y. Li, H.M. Huang, C. Wang, Solid State Phenom. 121 (2007) 123. D. Li, Y. Xia, Adv. Mater. 16 (2004) 1151. H. Hou, D.H. Reneker, Adv. Mater. 16 (2004) 69. H. Dong, E. Fey, A. Gandelman, W.E. Jones Jr., Chem. Mater. 18 (2006) 2008. F. Dong, Z. Li, H. Huang, F. Yang, W. Zheng, C. Wang, Mater. Lett. 61 (2007) 6556. C. Drew, X. Liu, D. Ziegler, X. Wang, F.F. Bruno, J. Whitten, Nano Lett. 3 (2003) 143. R.A. Abramovitch, Org. Prep. Proced. Int. 23 (1991) 683. J.R.J. Paré, J.M.R. Belanger, S.S. Stafford, Trends Anal. Chem. 13 (1994) 176. W.Y. Yu, W.X. Tu, H.F. Liu, Langmuir 15 (1999) 6. W.X. Tu, H.F. Liu, Chem. Mater. 12 (2000) 564. D. Bera, S.C. Kuiry, M. McCutchen, S. Seal, H. Heinrich, J. Appl. Phys. 96 (2004) 5153. W.X. Tu, H.F. Liu, J. Mater. Chem. 10 (2000) 2207.