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Preparation of ultra-fine fiber mats contained H4SiW12O40
Inorganic Chemistry Communications 6 (2003) 916–918 www.elsevier.com/locate/inoche
Preparation of ultra-fine fiber mats contained H4SiW12O40 Jian Gong *, Chang-Lu Shao, Guo-Cheng Yang, Yan Pan, Lun-Yu Qu Department of Chemistry, Northeast Normal University, Changchun 130024, China Received 17 January 2003; accepted 12 April 2003
Abstract For the first time, poly(vinyl alcohol) (PVA)/H4 SiW12 O40 ultra-fine fiber mats (80 wt% H4 SiW12 O40 ) was prepared by electrospinning technique. Calcining the PVA/HPA fiber mats at 380 °C for 4 h got pure H4 SiW12 O40 ultra-fine fiber mats. Ó 2003 Elsevier Science B.V. All rights reserved.
Hybrid inorganic–organic fiber mats have obtained more attention recently [1,2]. These materials can be designed as candidates for a number of applications including reinforcement in transparent composites, nanoelectronics, biomedical applications [3], and catalysis [4]. Usually, thin fibers of various materials have many novel properties. For examples, in composite applications, if there is a refractive index difference between fiber and matrix, the resulting composite becomes opaque or nontransparent due to light scattering [5]. One possible way of circumventing this limitation would be to use fibers with a diameter significantly smaller than the wavelength of visible light. Other excellent examples are thin fibers for filter applications [6], fiber mats serving as reinforcing component in composite system [5], biomedical applications [7], and template for the preparation of functional nanotubes [8]. As a result, making polymer/inorganic composite extra thin fibers will combine the advantages of organic–inorganic hybrids and thin fibers together, and meet the need of new materials. Heteropolyacid has been extensively studied as catalyst for many reactions and industrial application [9,10]. A main disadvantage, however, is its very low surface area [11]. Electrospinning is unique as a fiber spinning process that produces continuous fiber mats with nanoscale diameter [12]. Nonwoven fabrics composed of electrospun fibers have a large specific surface area and small pore size in comparison with commercial textiles. The morphology of fibers depends on the process *
Corresponding author. E-mail address: [email protected] (J. Gong).
parameters, including the solution concentration, applied electric field strength, deposition distance and deposition time [13,14]. In order to prepare fiber mats contained heteropolyacid by electrospinning technique and increase surface area of heteropolyacid, polymer needs to be used to increase viscosity of the solution. In this communication, we report the first PVA/H4 SiW12 O40 fiber mats prepared by electrospinning technique. For the first time, calcining the PVA/H4 SiW12 O40 fiber at 380 °C for 4 h gets pure H4 SiW12 O40 ultra fine fiber mats. The procedure employed for PVA/H4 SiW12 O40 fiber mats and pure H4 SiW12 O40 fiber mats were as follows. Aqueous PVA solution (20 g) of 10 wt% was added into 8 g of H4 SiW12 O40 with stirring for 24 h. The PVA/ H4 SiW12 O40 solution was placed in a plastic syringe at a fixed distance (8 cm) from a metal cathode. A copper pin connected to a high-voltage generator was placed in the solution; the negative terminal being attached to the aluminum foil target electrode, and the solution was kept in the capillary by adjusting the angle between capillary and the aluminum foil. The voltage applied between the anode and cathode was kept ca. 24 kV. The PVA/H4 SiW12 O40 (80 wt%) fiber mats were gotten in 8 h. The pure H4 SiW12 O40 ultra-fine fibers were gotten by calcining the PVA/ H4 SiW12 O40 fiber mats with a rate of 10 °C/min at 380 °C for 4 h. Elemental analysis showed that there was no carbon element in the PVA/ H4 SiW12 O40 fiber mats calcined at 380 °C for 4 h. This indicated that PVA had been decomposed and pure H4 SiW12 O40 fiber mats were gotten. The IR spectrum of PVA/H4 SiW12 O40 fiber mats showed four characteristic bands of H4 SiW12 O40 in the
1387-7003/03/$ - see front matter Ó 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S1387-7003(03)00148-5
J. Gong et al. / Inorganic Chemistry Communications 6 (2003) 916–918
Fig. 1. IR spectra of the different kinds of fiber mats.
range of 700–1100 cm 1 (Fig. 1) [15]. This indicated that H4 SiW12 O40 still kept Keggin structure in the PVA/ H4 SiW12 O40 fiber mats. Compared with the IR spectrum of H4 SiW12 O40 , the C@O stretching band (1600– 1800 cm 1 ) in the IR spectrum of PVA/H4 SiW12 O40 fiber mats became a broader band. This indicated the strong H-bonds between PVA and H4 SiW12 O40 [16]. The IR spectrum of the fiber mats calcined at 380 °C for 4 h showed the same as that of H4 SiW12 O40 . Obviously, pure H4 SiW12 O40 fiber was gotten after the PVA/ H4 SiW12 O40 fiber was calcined at 380 °C for 4 h. SEM photographs of the PVA/H4 SiW12 O40 fiber mats were investigated. The results indicated that the junctions of fibers decreased with increasing H4 SiW12 O40 content in PVA solution. We deduced that these apparent junctions were formed by overlap of fibers because of the viscosity of PVA solution. This also showed that the addition of H4 SiW12 O40 to PVA solution might obtain a homogenous species formed by the interaction between PVA and H4 SiW12 O40 molecules. Thus fiber mats with regular morphologies could be
Fig. 2. SEM of PVA/H4 SiW12 O40 fiber with 80 wt% H4 SiW12 O40 (a) and pure H4 SiW12 O40 ultra-fine fiber (b).
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prepared. In Figs. 2(a) and (b), the SEM photographs of the PVA/H4 SiW12 O40 fiber mats and PVA/H4 SiW12 O40 fiber mats calcined at 380 °C for 4 h were shown. As one could see, the PVA/H4 SiW12 O40 fiber mats calcined at 380 °C for 4 h still kept to the morphology and ultra-fine diameter of the fiber. The frequency distribution of the fiber matsÕ diameter was investigated. The result showed that the average diameter was 465 nm for PVA/ H4 SiW12 O40 fiber mats and 356 nm for PVA/ H4 SiW12 O40 fiber mats calcined at 380 °C for 4 h. Saying that the diameter of the fiber mats calcined at 380 °C for 4 h was thinner than that of the PVA/ H4 SiW12 O40 fiber mats. In Fig. 3, the XRD spectra of the PVA/H4 SiW12 O40 fiber mats and PVA/H4 SiW12 O40 fiber mats calcined at 380 °C for 4 h were shown. For PVA/H4 SiW12 O40 fiber mats, the characteristic peak of PVA was observed at about 20°, which corresponded to the (101) plane of PVA semi-crystalline [17]. At the same time, appearance of a peak at 2h < 10° indicated that the molecules of the fiber mats were ordered in short distance [18]. For the PVA/H4 SiW12 O40 fiber mats calcined at 380 °C for 4 h, there were four groupsÕ peaks in the ranges of 2h, 5–10°, 17–22°, 25–30°, and 31–37°, corresponding to the characteristic peaks of Keggin structure [19]. This result illustrated that pure H4 SiW12 O40 fiber mats (i.e., PVA/ H4 SiW12 O40 fiber mats calcined at 380 °C for 4 h) still kept Keggin structure. H4 SiW12 O:40 nH2 O powder, H4 SiW12 O40 /PVA fiber mats, and the PVA/H4 SiW12 O40 fiber mats calcined at 380 °C for 4 h were dried under vacuum at 50 °C for 24 h, respectively. Then, the BET of the sample was investigated. The results showed that the BET was 0.3 m2 / g for H4 SiW12 O40 powder, 4.1 m2 /g for PVA/HPA fiber mats, and 8.8 m2 /g for the PVA/H4 SiW12 O40 fiber mats
Fig. 3. XRD spectra of PVA/H4 SiW12 O40 fiber mats with 80 wt% H4 SiW12 O40 (a) and the PVA/H4 SiW12 O40 fiber mats calcined at 380 °C for 4 h (b).
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J. Gong et al. / Inorganic Chemistry Communications 6 (2003) 916–918
calcined at 380 °C for 4 h, respectively. The high BET surface area of the H4 SiW12 O40 fiber mats (i.e., the PVA/H4 SiW12 O40 fiber calcined at 380 °C for 4 h) could be applied as a promising catalyst in the coming future.
References [1] X.F. Qian, J. Yin, J.C. Huang, Y.F. Yang, X.X. Guo, Z.K. Zhe, Mater. Chem. Phys. 68 (2001) 95. [2] S. Hirano, T. Yogo, W. Sakamoto, S. Yamada, T. Nakamura, T. Yamanoto, H. Ukai, J. Eur. Ceram. Soc. 21 (2001) 1479. [3] J.M. Deitzel, W. Kosik, S.H. McKnight, N.C. Beck Tan, J.M. DeSimone, S. Crette, Polymer 43 (2002) 1025. [4] V.V. Ishtchenko, K.D. Huddersman, R.F. Vitkovskays, Appl. Catal. A: General (2002) in press. [5] M.M. Bergshoef, G..J. Vancso, Adv. Mater. 11 (1999) 1362. [6] M. Bognitzki, W. Czado, T. Frese, A. Schaper, M. Hellwig, M. Steinhart, A. Greiner, J.H. Wendorff, Adv. Mater. 13 (2001) 70. [7] E.L. Huang, R.A. Mcmillan, R.P. Apkarian, B. Pourdeyhimi, E.L. Chaikof, Macromolecules 33 (2000) 2989.
[8] M. Bognitzki, H. Hou, M. Ishaque, T. Frese, M. Hellwig, C. Schwarte, A. Schaper, J.H. Wendorff, A. Grwiner, Adv. Mater. 12 (2000) 637. [9] J.S. Choi, I.K. Song, W.Y. Lee, Catal. Today 67 (2001) 237. [10] L.E. Briand, H.J. Thomas, G.T. Baronetti, Appl. Catal. A: General 201 (2001) 191. [11] A. Molnar, C. Keresszegi, B. Torok, Appl. Catal. A: General 189 (1999) 217. [12] J.M. Deitzel, J.D. Kleinmeyer, D. Harris, T.N.C. Beck, Polymer 42 (2001) 261. [13] H. Fong, I. Chun, D.H. Reneker, Polymer 40 (1999) 4585. [14] J.M. Deitzel, J.D. Kleinmeyer, J.K. Hirvonen, T.N.C. Beck, Polymer 42 (2001) 8163. [15] J. Gong, X.J. Cui, Z.W. Xie, S.G.. Wang, L.Y. Qu, Synth. Metals 129 (2002) 187. [16] U.B. Mioc, S.K. Milonjic, D. Malovic, V. Stamenkovic, P. Colomban, M.M. Mitrovic, R. Dimitrijevic, Solid State Ionics 97 (1997) 239. [17] K. Nakane, T. Yamashita, K. Iwakura, F. Suzuki, J. Appl. Polym. Sci. 74 (1999) 133. [18] J. Gong, R.N. Hua, Z.W. Xie, S.G. Wang, L.Y. Qu, Polym. J. 33 (2001) 377. [19] Q.Y. Wu, G.Y. Meng, Solid State Ionics 273 (2000) 136.
Preparation of ultra-fine fiber mats contained H4SiW12O40 Jian Gong *, Chang-Lu Shao, Guo-Cheng Yang, Yan Pan, Lun-Yu Qu Department of Chemistry, Northeast Normal University, Changchun 130024, China Received 17 January 2003; accepted 12 April 2003
Abstract For the first time, poly(vinyl alcohol) (PVA)/H4 SiW12 O40 ultra-fine fiber mats (80 wt% H4 SiW12 O40 ) was prepared by electrospinning technique. Calcining the PVA/HPA fiber mats at 380 °C for 4 h got pure H4 SiW12 O40 ultra-fine fiber mats. Ó 2003 Elsevier Science B.V. All rights reserved.
Hybrid inorganic–organic fiber mats have obtained more attention recently [1,2]. These materials can be designed as candidates for a number of applications including reinforcement in transparent composites, nanoelectronics, biomedical applications [3], and catalysis [4]. Usually, thin fibers of various materials have many novel properties. For examples, in composite applications, if there is a refractive index difference between fiber and matrix, the resulting composite becomes opaque or nontransparent due to light scattering [5]. One possible way of circumventing this limitation would be to use fibers with a diameter significantly smaller than the wavelength of visible light. Other excellent examples are thin fibers for filter applications [6], fiber mats serving as reinforcing component in composite system [5], biomedical applications [7], and template for the preparation of functional nanotubes [8]. As a result, making polymer/inorganic composite extra thin fibers will combine the advantages of organic–inorganic hybrids and thin fibers together, and meet the need of new materials. Heteropolyacid has been extensively studied as catalyst for many reactions and industrial application [9,10]. A main disadvantage, however, is its very low surface area [11]. Electrospinning is unique as a fiber spinning process that produces continuous fiber mats with nanoscale diameter [12]. Nonwoven fabrics composed of electrospun fibers have a large specific surface area and small pore size in comparison with commercial textiles. The morphology of fibers depends on the process *
Corresponding author. E-mail address: [email protected] (J. Gong).
parameters, including the solution concentration, applied electric field strength, deposition distance and deposition time [13,14]. In order to prepare fiber mats contained heteropolyacid by electrospinning technique and increase surface area of heteropolyacid, polymer needs to be used to increase viscosity of the solution. In this communication, we report the first PVA/H4 SiW12 O40 fiber mats prepared by electrospinning technique. For the first time, calcining the PVA/H4 SiW12 O40 fiber at 380 °C for 4 h gets pure H4 SiW12 O40 ultra fine fiber mats. The procedure employed for PVA/H4 SiW12 O40 fiber mats and pure H4 SiW12 O40 fiber mats were as follows. Aqueous PVA solution (20 g) of 10 wt% was added into 8 g of H4 SiW12 O40 with stirring for 24 h. The PVA/ H4 SiW12 O40 solution was placed in a plastic syringe at a fixed distance (8 cm) from a metal cathode. A copper pin connected to a high-voltage generator was placed in the solution; the negative terminal being attached to the aluminum foil target electrode, and the solution was kept in the capillary by adjusting the angle between capillary and the aluminum foil. The voltage applied between the anode and cathode was kept ca. 24 kV. The PVA/H4 SiW12 O40 (80 wt%) fiber mats were gotten in 8 h. The pure H4 SiW12 O40 ultra-fine fibers were gotten by calcining the PVA/ H4 SiW12 O40 fiber mats with a rate of 10 °C/min at 380 °C for 4 h. Elemental analysis showed that there was no carbon element in the PVA/ H4 SiW12 O40 fiber mats calcined at 380 °C for 4 h. This indicated that PVA had been decomposed and pure H4 SiW12 O40 fiber mats were gotten. The IR spectrum of PVA/H4 SiW12 O40 fiber mats showed four characteristic bands of H4 SiW12 O40 in the
1387-7003/03/$ - see front matter Ó 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S1387-7003(03)00148-5
J. Gong et al. / Inorganic Chemistry Communications 6 (2003) 916–918
Fig. 1. IR spectra of the different kinds of fiber mats.
range of 700–1100 cm 1 (Fig. 1) [15]. This indicated that H4 SiW12 O40 still kept Keggin structure in the PVA/ H4 SiW12 O40 fiber mats. Compared with the IR spectrum of H4 SiW12 O40 , the C@O stretching band (1600– 1800 cm 1 ) in the IR spectrum of PVA/H4 SiW12 O40 fiber mats became a broader band. This indicated the strong H-bonds between PVA and H4 SiW12 O40 [16]. The IR spectrum of the fiber mats calcined at 380 °C for 4 h showed the same as that of H4 SiW12 O40 . Obviously, pure H4 SiW12 O40 fiber was gotten after the PVA/ H4 SiW12 O40 fiber was calcined at 380 °C for 4 h. SEM photographs of the PVA/H4 SiW12 O40 fiber mats were investigated. The results indicated that the junctions of fibers decreased with increasing H4 SiW12 O40 content in PVA solution. We deduced that these apparent junctions were formed by overlap of fibers because of the viscosity of PVA solution. This also showed that the addition of H4 SiW12 O40 to PVA solution might obtain a homogenous species formed by the interaction between PVA and H4 SiW12 O40 molecules. Thus fiber mats with regular morphologies could be
Fig. 2. SEM of PVA/H4 SiW12 O40 fiber with 80 wt% H4 SiW12 O40 (a) and pure H4 SiW12 O40 ultra-fine fiber (b).
917
prepared. In Figs. 2(a) and (b), the SEM photographs of the PVA/H4 SiW12 O40 fiber mats and PVA/H4 SiW12 O40 fiber mats calcined at 380 °C for 4 h were shown. As one could see, the PVA/H4 SiW12 O40 fiber mats calcined at 380 °C for 4 h still kept to the morphology and ultra-fine diameter of the fiber. The frequency distribution of the fiber matsÕ diameter was investigated. The result showed that the average diameter was 465 nm for PVA/ H4 SiW12 O40 fiber mats and 356 nm for PVA/ H4 SiW12 O40 fiber mats calcined at 380 °C for 4 h. Saying that the diameter of the fiber mats calcined at 380 °C for 4 h was thinner than that of the PVA/ H4 SiW12 O40 fiber mats. In Fig. 3, the XRD spectra of the PVA/H4 SiW12 O40 fiber mats and PVA/H4 SiW12 O40 fiber mats calcined at 380 °C for 4 h were shown. For PVA/H4 SiW12 O40 fiber mats, the characteristic peak of PVA was observed at about 20°, which corresponded to the (101) plane of PVA semi-crystalline [17]. At the same time, appearance of a peak at 2h < 10° indicated that the molecules of the fiber mats were ordered in short distance [18]. For the PVA/H4 SiW12 O40 fiber mats calcined at 380 °C for 4 h, there were four groupsÕ peaks in the ranges of 2h, 5–10°, 17–22°, 25–30°, and 31–37°, corresponding to the characteristic peaks of Keggin structure [19]. This result illustrated that pure H4 SiW12 O40 fiber mats (i.e., PVA/ H4 SiW12 O40 fiber mats calcined at 380 °C for 4 h) still kept Keggin structure. H4 SiW12 O:40 nH2 O powder, H4 SiW12 O40 /PVA fiber mats, and the PVA/H4 SiW12 O40 fiber mats calcined at 380 °C for 4 h were dried under vacuum at 50 °C for 24 h, respectively. Then, the BET of the sample was investigated. The results showed that the BET was 0.3 m2 / g for H4 SiW12 O40 powder, 4.1 m2 /g for PVA/HPA fiber mats, and 8.8 m2 /g for the PVA/H4 SiW12 O40 fiber mats
Fig. 3. XRD spectra of PVA/H4 SiW12 O40 fiber mats with 80 wt% H4 SiW12 O40 (a) and the PVA/H4 SiW12 O40 fiber mats calcined at 380 °C for 4 h (b).
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J. Gong et al. / Inorganic Chemistry Communications 6 (2003) 916–918
calcined at 380 °C for 4 h, respectively. The high BET surface area of the H4 SiW12 O40 fiber mats (i.e., the PVA/H4 SiW12 O40 fiber calcined at 380 °C for 4 h) could be applied as a promising catalyst in the coming future.
References [1] X.F. Qian, J. Yin, J.C. Huang, Y.F. Yang, X.X. Guo, Z.K. Zhe, Mater. Chem. Phys. 68 (2001) 95. [2] S. Hirano, T. Yogo, W. Sakamoto, S. Yamada, T. Nakamura, T. Yamanoto, H. Ukai, J. Eur. Ceram. Soc. 21 (2001) 1479. [3] J.M. Deitzel, W. Kosik, S.H. McKnight, N.C. Beck Tan, J.M. DeSimone, S. Crette, Polymer 43 (2002) 1025. [4] V.V. Ishtchenko, K.D. Huddersman, R.F. Vitkovskays, Appl. Catal. A: General (2002) in press. [5] M.M. Bergshoef, G..J. Vancso, Adv. Mater. 11 (1999) 1362. [6] M. Bognitzki, W. Czado, T. Frese, A. Schaper, M. Hellwig, M. Steinhart, A. Greiner, J.H. Wendorff, Adv. Mater. 13 (2001) 70. [7] E.L. Huang, R.A. Mcmillan, R.P. Apkarian, B. Pourdeyhimi, E.L. Chaikof, Macromolecules 33 (2000) 2989.
[8] M. Bognitzki, H. Hou, M. Ishaque, T. Frese, M. Hellwig, C. Schwarte, A. Schaper, J.H. Wendorff, A. Grwiner, Adv. Mater. 12 (2000) 637. [9] J.S. Choi, I.K. Song, W.Y. Lee, Catal. Today 67 (2001) 237. [10] L.E. Briand, H.J. Thomas, G.T. Baronetti, Appl. Catal. A: General 201 (2001) 191. [11] A. Molnar, C. Keresszegi, B. Torok, Appl. Catal. A: General 189 (1999) 217. [12] J.M. Deitzel, J.D. Kleinmeyer, D. Harris, T.N.C. Beck, Polymer 42 (2001) 261. [13] H. Fong, I. Chun, D.H. Reneker, Polymer 40 (1999) 4585. [14] J.M. Deitzel, J.D. Kleinmeyer, J.K. Hirvonen, T.N.C. Beck, Polymer 42 (2001) 8163. [15] J. Gong, X.J. Cui, Z.W. Xie, S.G.. Wang, L.Y. Qu, Synth. Metals 129 (2002) 187. [16] U.B. Mioc, S.K. Milonjic, D. Malovic, V. Stamenkovic, P. Colomban, M.M. Mitrovic, R. Dimitrijevic, Solid State Ionics 97 (1997) 239. [17] K. Nakane, T. Yamashita, K. Iwakura, F. Suzuki, J. Appl. Polym. Sci. 74 (1999) 133. [18] J. Gong, R.N. Hua, Z.W. Xie, S.G. Wang, L.Y. Qu, Polym. J. 33 (2001) 377. [19] Q.Y. Wu, G.Y. Meng, Solid State Ionics 273 (2000) 136.