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Preparation of nanoporous SiOx materials via interpenetrating polymer network method
Materials Letters 57 (2003) 3606 – 3608 www.elsevier.com/locate/matlet
Preparation of nanoporous SiOx materials via interpenetrating polymer network method Qingchun Zhao a,b,*, Wenming Chen a,b, Qingren Zhu a a
Structure Research Laboratory, University of Science and Technology of China, Academia Sinica, Hefei 230026 Anhui, People’s Republic of China b Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026 Anhui, People’s Republic of China Received 28 December 2002; accepted 8 January 2003
Abstract In this letter, polyacrylamide gels with SiO23 and Na+ ions in the porous were prepared by using free-radical aqueous polymerization method. Nanoporous SiOx materials were prepared by heating the polyacrylamide gels with colloid of silicic acid in porous to 600 jC and held at this temperature for 24 h. The porous size of nanoporous SiOx materials in the obtained samples was investigated by scanning electron microscopy (SEM) and the average porous size is 50 nm in diameter. From SEM image, we can see the porous size distribution is narrow, but the porous array is irregular. Nanoporous SiOx materials were investigated from the X-ray photoelectron spectra (XPS) spectra and infrared spectrum of the obtained samples. The chemical mechanism for the formation of nanoporous SiOx materials is discussed. D 2003 Elsevier Science B.V. All rights reserved. Keywords: Interpenetrating polymer network; Nanoporous SiOx materials
Since the discovery of the mesoporous molecular sieves MCM-41 [1], these materials have been extensively investigated in many potential applications in catalysis, separation, coating, microelectronics and electrooptics, [2– 4] several different synthesis strategies have been proposed and successfully used to prepare mesoporous materials with a unique pore size distribution. Bagshaw et al. [5] prepared mesoporous molecular sieves using polyethylenoxide as a surfactant. Templin et al. [6] used block copolymer phases * Corresponding author. Structure Research Laboratory, University of Science and Technology of China, Academia Sinica, Hefei 230026, Anhui, People’s Republic of China. E-mail address: [email protected] (Q. Zhao).
for the synthesis of aluminosilicate mesostructures with different morphologies. Beck et al. [7] reported to prepare MCM-48 materials by a self-assembly process based on the electrostatic interaction between positively charged quaternary ammonium micelles (S+) and inorganic anions (I ). It is well known that the polyacrylamide gels are three-dimensional network structure. In this letter, nanoporous SiOx materials were prepared by using interpenetrating polymer network method. This will offer a facile method to prepare nanoporous materials in the material field. Gels of acrylamide with SiO32 and Na+ ions in the porous were prepared by free radical polymerization in water using g rays as initiator. Total concentration
0167-577X/03/$ - see front matter D 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0167-577X(03)00134-4
Q. Zhao et al. / Materials Letters 57 (2003) 3606–3608
3607
of monomer, T (T = A + B, where A and B are concentration of acrylamide and Na2SiO3, A is 10) is 30%. After the solutions were bubbled with N2 for 20 min to eliminate oxygen, they were irradiated by g rays with 2000 Gy. After the polyacrylamide gels were obtained and were immersed in 1 mol l 1 H2SO4 solutions for 3 days, colloid of silicic acid was produced in porous of the polyacrylamide gels and the interpenetrating network polymers were produced. The interpenetrating network polymers were taken out and were washed with water until there are no Na+ and SO42 ions in the porosity of the interpenetrating network polymers; the interpenetrating network polymers were heated to 600 jC and held at this temperature for 24 h. The polyacrylamide gels were degradated, volatilized and oxidized by high temperature and oxygen, and high pure nanoporous SiOx materials were obtained. The synthesized products were characterized by scanning electron microscopy (SEM) (JEOL JSM6300); X-ray photoelectron spectra (XPS) were acquired in VG ESCALAB MKII instrument in which Mg K-Aipha was employed. Infrared spectrum is carried out on a Bruker FT-IR (Vector 22). In Fig. 1, SEM observation shows that they are a large quantity of porous with average diameter 50 nm in the obtained samples and the porous array is irregular. A key question here is why the amorphous material is formed in nanoporous materials. The most likely
Fig. 2. XPS spectra of nanoporous SiOx materials: (a) survey spectrum; (b) O (1s) binding energy spectrum; (c) Si (2p) binding energy spectrum.
Fig. 1. SEM image of typical nanoporous SiOx materials.
mechanism to explain the growth of the nanoporous materials may be the control of the network of the polyacrylamide gels. It is well known that polyacrylamide gels are three-dimensional network structure. When polyacrylamide gels with SiO32 and Na+ ions
3608
Q. Zhao et al. / Materials Letters 57 (2003) 3606–3608
in the porous were immersed into the 1 mol l 1H2SO4 solutions. Colloid of silicic acid was produced in porous of the polyacrylamide gels and formed interpenetrating polymer network. After the interpenetrating network polymer were heated to 600 jC and held at this temperature for 24 h, the polyacrylamide gels were degradated, volatilized and oxidized by high temperature and oxygen, and high pure nanoporous SiOx materials were obtained and the nanoporous may formed by the polyacrylamide molecular chains. The X-ray photoelectron spectroscopy (XPS) in Fig. 2 displays mainly the oxygen and silicon peaks. Quantification of these peaks reveals that the atomic ratio of O to Si is about 7:3. This spectrum does not display a C (1s) peak and this means the polyacrylamide gels were entirely degradated, volatilized and oxidized by high temperature and oxygen. The typical Si (2p) peak (at 103.6 eV) indicates that the SiOx microspheres are composed of silicon. An obvious peak is observed in the O (1s) spectrum (at 532.6 eV), meaning there are SiUO and OH bonds. Typical infrared spectrum of obtained samples is shown in Fig. 3. There are two strong absorption bands. The absorption peak at 3441 cm 1 can be attributed to the vibration mode of SiUOH, while the other at around 1111.4 cm 1 is due to the absorption of SiUO groups [8]. The CUH stretching vibrations at 2857 and 2928 cm 1 are not observed in our samples. This mean the polyacrylamide gels were entirely degradated, volatilized and oxidized by oxygen and high temperature. The obtained samples belong to oxygen surplus silica and the atomic ratio of O to Si is about 7:3. In summary, interpenetrating polymer network method has been successfully used to prepare nanoporous SiOx materials, but there are some questions, for example, the porous array is irregular and this problem will be further investigated. This approach
Fig. 3. The typical infrared spectrum of obtained nanoporous SiOx materials.
provides a new chemical route to the fabrication of semiconductor nanoporous SiOx materials, which may find applications in many technological fields.
References [1] C.T. Kresge, M.E. Leonowicz, W.J. Roth, J.C. Vaituli, J.S. Beck, Nature 359 (1992) 710. [2] C.C. Wu, T. Bein, Science 266 (1994) 1013. [3] F. Marlow, M.D. Mcgehee, D. Zhao, B.F. Chmelka, G.D. Stucky, Adv. Mater. 11 (1999) 632. [4] S. Mann, G.A. Ozin, Nature 382 (1996) 313. [5] S.A. Bagshaw, E. Prouzet, T.J. Pinnavaia, Science 269 (1995). [6] M. Templin, A. Franck, A.Du. Chense, H. Leist, Y. Zhang, R. Ulrich, V. Scha¨ndler, U. Wiesner, Science 278 (1997). [7] J.S. Beck, J.C. Vartuli, W.J. Roth, M.E. Leonowicz, C.T. Kresge, K.D. Schimitt, C.T.W. Chu, D.H. Olson, E.W. Sheppard, E.B. Mccullen, J.B. Higgins, J.L. Schlenker, J. Am. Chem. Soc. 114 (1992) 10834. [8] G. Socrates, Infrared Characteristic Group Frequencies, Wiley, New York, 1980, p. 129.
Preparation of nanoporous SiOx materials via interpenetrating polymer network method Qingchun Zhao a,b,*, Wenming Chen a,b, Qingren Zhu a a
Structure Research Laboratory, University of Science and Technology of China, Academia Sinica, Hefei 230026 Anhui, People’s Republic of China b Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026 Anhui, People’s Republic of China Received 28 December 2002; accepted 8 January 2003
Abstract In this letter, polyacrylamide gels with SiO23 and Na+ ions in the porous were prepared by using free-radical aqueous polymerization method. Nanoporous SiOx materials were prepared by heating the polyacrylamide gels with colloid of silicic acid in porous to 600 jC and held at this temperature for 24 h. The porous size of nanoporous SiOx materials in the obtained samples was investigated by scanning electron microscopy (SEM) and the average porous size is 50 nm in diameter. From SEM image, we can see the porous size distribution is narrow, but the porous array is irregular. Nanoporous SiOx materials were investigated from the X-ray photoelectron spectra (XPS) spectra and infrared spectrum of the obtained samples. The chemical mechanism for the formation of nanoporous SiOx materials is discussed. D 2003 Elsevier Science B.V. All rights reserved. Keywords: Interpenetrating polymer network; Nanoporous SiOx materials
Since the discovery of the mesoporous molecular sieves MCM-41 [1], these materials have been extensively investigated in many potential applications in catalysis, separation, coating, microelectronics and electrooptics, [2– 4] several different synthesis strategies have been proposed and successfully used to prepare mesoporous materials with a unique pore size distribution. Bagshaw et al. [5] prepared mesoporous molecular sieves using polyethylenoxide as a surfactant. Templin et al. [6] used block copolymer phases * Corresponding author. Structure Research Laboratory, University of Science and Technology of China, Academia Sinica, Hefei 230026, Anhui, People’s Republic of China. E-mail address: [email protected] (Q. Zhao).
for the synthesis of aluminosilicate mesostructures with different morphologies. Beck et al. [7] reported to prepare MCM-48 materials by a self-assembly process based on the electrostatic interaction between positively charged quaternary ammonium micelles (S+) and inorganic anions (I ). It is well known that the polyacrylamide gels are three-dimensional network structure. In this letter, nanoporous SiOx materials were prepared by using interpenetrating polymer network method. This will offer a facile method to prepare nanoporous materials in the material field. Gels of acrylamide with SiO32 and Na+ ions in the porous were prepared by free radical polymerization in water using g rays as initiator. Total concentration
0167-577X/03/$ - see front matter D 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0167-577X(03)00134-4
Q. Zhao et al. / Materials Letters 57 (2003) 3606–3608
3607
of monomer, T (T = A + B, where A and B are concentration of acrylamide and Na2SiO3, A is 10) is 30%. After the solutions were bubbled with N2 for 20 min to eliminate oxygen, they were irradiated by g rays with 2000 Gy. After the polyacrylamide gels were obtained and were immersed in 1 mol l 1 H2SO4 solutions for 3 days, colloid of silicic acid was produced in porous of the polyacrylamide gels and the interpenetrating network polymers were produced. The interpenetrating network polymers were taken out and were washed with water until there are no Na+ and SO42 ions in the porosity of the interpenetrating network polymers; the interpenetrating network polymers were heated to 600 jC and held at this temperature for 24 h. The polyacrylamide gels were degradated, volatilized and oxidized by high temperature and oxygen, and high pure nanoporous SiOx materials were obtained. The synthesized products were characterized by scanning electron microscopy (SEM) (JEOL JSM6300); X-ray photoelectron spectra (XPS) were acquired in VG ESCALAB MKII instrument in which Mg K-Aipha was employed. Infrared spectrum is carried out on a Bruker FT-IR (Vector 22). In Fig. 1, SEM observation shows that they are a large quantity of porous with average diameter 50 nm in the obtained samples and the porous array is irregular. A key question here is why the amorphous material is formed in nanoporous materials. The most likely
Fig. 2. XPS spectra of nanoporous SiOx materials: (a) survey spectrum; (b) O (1s) binding energy spectrum; (c) Si (2p) binding energy spectrum.
Fig. 1. SEM image of typical nanoporous SiOx materials.
mechanism to explain the growth of the nanoporous materials may be the control of the network of the polyacrylamide gels. It is well known that polyacrylamide gels are three-dimensional network structure. When polyacrylamide gels with SiO32 and Na+ ions
3608
Q. Zhao et al. / Materials Letters 57 (2003) 3606–3608
in the porous were immersed into the 1 mol l 1H2SO4 solutions. Colloid of silicic acid was produced in porous of the polyacrylamide gels and formed interpenetrating polymer network. After the interpenetrating network polymer were heated to 600 jC and held at this temperature for 24 h, the polyacrylamide gels were degradated, volatilized and oxidized by high temperature and oxygen, and high pure nanoporous SiOx materials were obtained and the nanoporous may formed by the polyacrylamide molecular chains. The X-ray photoelectron spectroscopy (XPS) in Fig. 2 displays mainly the oxygen and silicon peaks. Quantification of these peaks reveals that the atomic ratio of O to Si is about 7:3. This spectrum does not display a C (1s) peak and this means the polyacrylamide gels were entirely degradated, volatilized and oxidized by high temperature and oxygen. The typical Si (2p) peak (at 103.6 eV) indicates that the SiOx microspheres are composed of silicon. An obvious peak is observed in the O (1s) spectrum (at 532.6 eV), meaning there are SiUO and OH bonds. Typical infrared spectrum of obtained samples is shown in Fig. 3. There are two strong absorption bands. The absorption peak at 3441 cm 1 can be attributed to the vibration mode of SiUOH, while the other at around 1111.4 cm 1 is due to the absorption of SiUO groups [8]. The CUH stretching vibrations at 2857 and 2928 cm 1 are not observed in our samples. This mean the polyacrylamide gels were entirely degradated, volatilized and oxidized by oxygen and high temperature. The obtained samples belong to oxygen surplus silica and the atomic ratio of O to Si is about 7:3. In summary, interpenetrating polymer network method has been successfully used to prepare nanoporous SiOx materials, but there are some questions, for example, the porous array is irregular and this problem will be further investigated. This approach
Fig. 3. The typical infrared spectrum of obtained nanoporous SiOx materials.
provides a new chemical route to the fabrication of semiconductor nanoporous SiOx materials, which may find applications in many technological fields.
References [1] C.T. Kresge, M.E. Leonowicz, W.J. Roth, J.C. Vaituli, J.S. Beck, Nature 359 (1992) 710. [2] C.C. Wu, T. Bein, Science 266 (1994) 1013. [3] F. Marlow, M.D. Mcgehee, D. Zhao, B.F. Chmelka, G.D. Stucky, Adv. Mater. 11 (1999) 632. [4] S. Mann, G.A. Ozin, Nature 382 (1996) 313. [5] S.A. Bagshaw, E. Prouzet, T.J. Pinnavaia, Science 269 (1995). [6] M. Templin, A. Franck, A.Du. Chense, H. Leist, Y. Zhang, R. Ulrich, V. Scha¨ndler, U. Wiesner, Science 278 (1997). [7] J.S. Beck, J.C. Vartuli, W.J. Roth, M.E. Leonowicz, C.T. Kresge, K.D. Schimitt, C.T.W. Chu, D.H. Olson, E.W. Sheppard, E.B. Mccullen, J.B. Higgins, J.L. Schlenker, J. Am. Chem. Soc. 114 (1992) 10834. [8] G. Socrates, Infrared Characteristic Group Frequencies, Wiley, New York, 1980, p. 129.