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Nanomorphological anatase TiO2: From spongy network to porous nanoparticles
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Materials Letters 62 (2008) 1896 – 1898 www.elsevier.com/locate/matlet
Nanomorphological anatase TiO2: From spongy network to porous nanoparticles Xingtao Jia a,b , Wen He b,⁎, Wei Yang a , Hongshi Zhao b , Xudong Zhang b a
b
College of Chemistry & Chemical Engineering, China University of Petroleum, Dongying, 257061, China Department of Materials Science and Engineering, Shandong Institute of Light Industry, Jinan, 250353, China Received 19 July 2007; accepted 18 October 2007 Available online 24 October 2007
Abstract Nanomorphological anatase TiO2 from spongy network to porous nanoparticles was synthesized by a modified sol–gel preparation and a post microwave-assisted combustion treatment. The TEM studies showed that the spongy network texture was resulted in sample calcined at lower temperature (360 °C) and the structure partially collapsed into solid and porous nanoparticles when calcined at higher temperature (400 °C). The photocatalysis study showed that the lower calcinations sample is photo-inactive large adsorbed of methyl orange than P25. The special texture, large adsorption of organ molecular and photo-inactivity of the lower calcinations sample indicated that the materials maybe served as a kind of promising biomimetic material. © 2007 Elsevier B.V. All rights reserved. Keywords: Spongy network structure; Nanomaterials; Sol–gel preparation; TiO2; Biomaterial
1. Introduction Nanomorphological TiO2 are of both theoretical and technological interest for their novel properties in using as catalyst and photocatalyst, chemical sensors and solar cell electrodes, hydrogen storage materials, organ and tissue materials and so on [1–5]. Generally speaking, materials with different morphologies would show different properties. Such as TiO2 nanotube is a good candidate as solar cell electrode, and mesoporous TiO2 is a kind of host material and shows enhanced photocatalysis [6–11]. To develop new functionalities, it is always a good strategy to modulate the compositions, morphologies and texture of the traditional materials. Comparing to traditional synthesis, evaporation induced self-assembly (EISA) had been demonstrated to be a powerful method to prepare materials with different morphologies [12,13]. Microwaveassisted synthesis has been widely used in synthetic chemistry since 1986, which is advantageous in reduction of reaction time ⁎ Corresponding author. Tel.: +86 531 8963 1231; fax: +86 531 8963 1226. E-mail addresses: [email protected] (X. Jia), [email protected] (W. He), [email protected] (W. Yang), [email protected] (H. Zhao), [email protected] (X. Zhang). 0167-577X/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2007.10.034
by orders of magnitude, higher production efficiency, higher uniformity and higher property [14]. Unfortunately the combination of the two techniques in one synthesis was seldom explored, although some synthesis demonstrated that the method is simple and powerful to realize in situ synthesis [15–17]. In the synthesis, nanomorphological anatase TiO2 from spongy network to porous nanoparticles was obtained by an EISA synthesis and microwave-assisted combustion treatment. TEM studies showed an evolution from spongy network structure to porous solid nanoparticle when change the calcinations temperature. The spongy sample shows good adsorption of small organ molecular and photo-inactivity. 2. Experimental Anatase TiO2 powders were synthesized by a modified EISA synthesis and a post microwave-assisted treatment [12,13]. In a typical synthesis, tri-block copolymer surfactant P123 was dissolved into a diluted hydrochloric acid (HCl)–ethanol (EtOH) solution and stirred for 30 min, the resultant transparent solution was labeled as A; at the same time, titanium tetraethoxide (TBOT) was dropped into diluted HCl–EtOH solution, and the demonized water was added dropwise after
X. Jia et al. / Materials Letters 62 (2008) 1896–1898
15 min vigorous stirring, the resultant light yellow solution was labeled as B. Then, solution B was added into A and stirred 30 min, a transparent sol with molar composition TBOT/P123/ HCl/H2O/EtOH = 1:0.002:4:8:30 was resulted. After keeping stationary for 30 min, the stock solution was transferred into a petri dish, and crack-free membranes were obtained after aged at 40 °C for 7 days in air. The as-prepared membranes were collected and transferred into a microwave oven (Glanz WP800L23-3), a self-propagation combustion was ignited at once when fired under high-power microwave. Lower temperature calcinations were treated at 360 °C with heating rate 2.5 °C/min and held the temperature for 3.5 h, higher temperature calcination was treated at 400 °C for 3.5 h with heating rate 20 °C/min. The crystalline structure was investigated by X-ray diffraction (XRD) on a D/max-ra X-ray diffractometer with Cu Kα radiation (λ = 0.15418 nm) and graphite monochromator. The morphologies were studied on a TEM-100X transition electron microscope. Brunauer–Emett–Teller (BET) method was used for the specific surface area investigation on ST-08A metering
1897
system. The photocatalysis was carried on self-designed equipment; 40 W/220 V UV lamp (365 nm) was used as luminous source and methyl orange as reactant. 3. Results and discussion Anatase TiO2 with morphologies from spongy network structure to porous nanoparticles was synthesized by a modified EISA method and a microwave-assisted combustion treatment. TEM photographs of sample calcined at 360 °C and 400 °C were shown in Fig. 1(a, b, c) and Fig. 1(d, e, f) respectively. In lower temperature calcinations samples (Fig. 1(a, b, c)), there showed the spongy network structure and large pores. Unfortunately, the spongy network texture was degenerated into porous nanoparticles when sintered under higher temperature (Fig. 1(e, f)). In higher resolution photograph (Fig. 1(c)) there showed some build-in pores, we supposed that the smaller pores merge into a larger one (Fig. 1(d)) when elevated the calcinations temperature. The selected area electron diffraction (SAED) image of the lower temperature calcinations samples was shown in the insert of Fig. 1 (a), therein unclearly diffraction halos were shown indicating poor crystallization. The detail image (Fig. 1(f)) of solid nanoparticles in
Fig. 1. TEM photographs of the sample calcined at 360 °C (a)–(c) and 400 °C (d)–(f). Insert images of (a) and (e) are selected area electron diffraction (SAED) patterns of sample calcined at 360 °C and 400 °C respectively. (Scale bar in all photographs is 100 nm).
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texture would effectively diminish the probability of organ rejection that often happened during the tissue and organ transplantation. So, we considered that the spongy network structure TiO2 in our study might find use as biomimetic material.
4. Conclusions
Fig. 2. Wide-angle XRD patterns of the sample calcined at 360 °C (a) and 400 °C (b).
Fig. 1(d, e) indicated loose texture of the nanoparticles. The clearly diffraction rings in the insert of Fig. 1(e) indicated that the loose texture was well-crystallized (Fig. 1(e)), this was different with the normal compact nanoparticle morphology without the using of surfactant in the synthesis, indicated that the surfactant plays roles in the formation of the nanomorphologies. In a word, the lower temperature calcinations sample showed spongy network structure but poor-crystallized; and the higher temperature sample showed loose texture and well-crystallized. The wide-angle XRD patterns of sample calcined at 360 °C and 400 °C were shown in Fig. 2. The sample calcined at 400 °C showed sharp and broad peak, indicating well-crystallized and small crystalline size. The particles diameter of sample calculated according the halfwidth at the full maximum (HWFM) of (101) peak was 8.0 nm, and consistent well with large specific area of the sample (120 m2 g− 1). Comparatively, the sample calcined at 360 °C showed a broad halo, indicated that TiO2 nanocrystalline is smaller and macroscopic amorphous. The lower temperature calcination sample had larger specific area (275 m2 g− 1) than higher one. The photocatalysis was performed on self-designed equipment. The results showed that the sample calcined at 360 °C is photo-inactive; this was consistent well with the amorphous and poor-crystallized structure. The sample calcined at 400 °C showed good photocatalysis activity but weaker than the commercial P25. We supposed that the wellcrystallized mixed crystalline structure (75% anatase and 25% rutile) of P25 would be responsible for the photocatalysis superiority, although our sample calcined at 400 °C has larger specific areas (P25 is 50 m2 g− 1) and also good crystallized. The UV spectrums of the sample calcined at 360 °C and 400 °C showed large red shift than commercial P25, this was consistent with the amorphous structure of sample calcined at 360 °C and smaller crystalline size of sample calcined at 400 °C. The larger red shift of our sample than commercial P25 would be another reason for lower photocatalytic activity. Interestingly, larger methyl orange adsorption amount was observed in our sample calcined at 360 °C (1.75 mg g− 1) than the commercial P25 (0.5 mg/g) in our photocatalysis experiment, this was consistent with the larger specific area and amorphous spongy network structure of our sample, indicating a biomimetic usage. It has been demonstrated that nanocrystalline TiO2 is a potential candidate as an implantation material for its good mechanical property, nontoxicity and compatibility with organ and tissue. By forming an organic–inorganic interpenetrating network structures, TiO2 with spongy network structure would be more favorable to serve as the implantation material for human organ and tissue, for the special
In the study, nanomorphological anatase TiO2 from spongy network structure to porous nanoparticles was synthesized by a modified EISA method and a post microwave-assisted combustion treatment. The TEM studies showed that the spongy network structure formed at lower calcined temperature (360 °C) would partially collapsed into nanoparticles when elevated the calcination temperature (400 °C). The lower temperature calcination sample showed larger BET specific surface area (275 m2 g− 1) than higher sample (120 m2 g− 1). The photocatalysis investigation showed that the lower calcinations sample is photo-inactive and large adsorption of methyl orange. The spongy network structure, large organ molecular adsorption ability and photo-inactivity indicated that the material may find use as biomimetic material. Acknowledgement Thanks to the support from the Shandong Province Science Foundation under Award No. Y2002F20 and No. Y2003F02. We are grateful to Professor Jinshui Yao, Yuqing Chen, Suwen Li and Jianxing Shen for helpful discussions and technical assistance. References [1] M.R. Hoffmann, S.T. Martin, W. Choi, D.W. Bahnemann, Chem. Rev. 95 (1995) 69–96. [2] M. Kunst, T. Moehl, F. Wunsch, H. Tributsch, Superlattice Microst. 39 (2006) 376–380. [3] S.M. Karvinen, Ind. Eng. Chem. Res. 42 (2003) 1035–1043. [4] J. Chen, S.L. Li, Z.L. Tao, Y.T. Shen, C.X. Cui, J. Am. Chem. Soc. 125 (2003) 5284–5285. [5] S. Rana, J. Rawat, M.M. Sorensson, R.D. Misra, Acta Biomater. 2 (2006) 421–432. [6] G.K. Mor, K. Shankar, M. Paulose, O.K. Varghese, C.A. Grimes, Nano Lett. 5 (2005) 191–195. [7] J.H. Park, S. Kim, A.J. Bard, Nano Lett. 6 (2006) 24–28. [8] N. Popovicia, E. Jimeneza, R.C. da Silvab, W.R. Branfordc, L.F. Cohenc, O. Condea, J. Non-Cryst. Solids 352 (2006) 1486–1489. [9] S.H. Toma, J.A. Bonacin, K. Araki, H.E. Toma, Surf. Sci. 600 (2006) 4591–4597. [10] M. Alvaro, C. Aprile, M. Benitez, E. Carbonell, H. Garcia, J. Phys. Chem., B 110 (2006) 6661–6665. [11] K.L. Frindell, J. Tang, J.H. Harreld, G.D. Stucky, Chem. Mater. 16 (2004) 3524–3532. [12] D. Zhao, P. Yang, N. Melosh, J. Feng, B.F. Chmelka, G.D. Stucky, Adv. Mater. 10 (1998) 1380–1385. [13] P. Yang, D. Zhao, D.I. Margolese, B.F. Chmelka, G.D. Stucky, Nature 396 (1998) 152–155. [14] R. Gedye, F. Smith, K. Westaway, A. Humera, L. Baldisera, L. Laberge, et al., Tetrahedron Lett. 27 (1986) 279–282. [15] J.C. Yu, X. Hu, Q. Li, L. Zhang, Chem. Commun. (2005) 2704–2706. [16] J.W. Mitchell, R.A. Holland, Mater. Lett. 60 (2006) 1524–1526. [17] M.N. Nadagouda, R.S. Varma, Smart Mater. Struct. 15 (2006) 1260–1265.
Materials Letters 62 (2008) 1896 – 1898 www.elsevier.com/locate/matlet
Nanomorphological anatase TiO2: From spongy network to porous nanoparticles Xingtao Jia a,b , Wen He b,⁎, Wei Yang a , Hongshi Zhao b , Xudong Zhang b a
b
College of Chemistry & Chemical Engineering, China University of Petroleum, Dongying, 257061, China Department of Materials Science and Engineering, Shandong Institute of Light Industry, Jinan, 250353, China Received 19 July 2007; accepted 18 October 2007 Available online 24 October 2007
Abstract Nanomorphological anatase TiO2 from spongy network to porous nanoparticles was synthesized by a modified sol–gel preparation and a post microwave-assisted combustion treatment. The TEM studies showed that the spongy network texture was resulted in sample calcined at lower temperature (360 °C) and the structure partially collapsed into solid and porous nanoparticles when calcined at higher temperature (400 °C). The photocatalysis study showed that the lower calcinations sample is photo-inactive large adsorbed of methyl orange than P25. The special texture, large adsorption of organ molecular and photo-inactivity of the lower calcinations sample indicated that the materials maybe served as a kind of promising biomimetic material. © 2007 Elsevier B.V. All rights reserved. Keywords: Spongy network structure; Nanomaterials; Sol–gel preparation; TiO2; Biomaterial
1. Introduction Nanomorphological TiO2 are of both theoretical and technological interest for their novel properties in using as catalyst and photocatalyst, chemical sensors and solar cell electrodes, hydrogen storage materials, organ and tissue materials and so on [1–5]. Generally speaking, materials with different morphologies would show different properties. Such as TiO2 nanotube is a good candidate as solar cell electrode, and mesoporous TiO2 is a kind of host material and shows enhanced photocatalysis [6–11]. To develop new functionalities, it is always a good strategy to modulate the compositions, morphologies and texture of the traditional materials. Comparing to traditional synthesis, evaporation induced self-assembly (EISA) had been demonstrated to be a powerful method to prepare materials with different morphologies [12,13]. Microwaveassisted synthesis has been widely used in synthetic chemistry since 1986, which is advantageous in reduction of reaction time ⁎ Corresponding author. Tel.: +86 531 8963 1231; fax: +86 531 8963 1226. E-mail addresses: [email protected] (X. Jia), [email protected] (W. He), [email protected] (W. Yang), [email protected] (H. Zhao), [email protected] (X. Zhang). 0167-577X/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2007.10.034
by orders of magnitude, higher production efficiency, higher uniformity and higher property [14]. Unfortunately the combination of the two techniques in one synthesis was seldom explored, although some synthesis demonstrated that the method is simple and powerful to realize in situ synthesis [15–17]. In the synthesis, nanomorphological anatase TiO2 from spongy network to porous nanoparticles was obtained by an EISA synthesis and microwave-assisted combustion treatment. TEM studies showed an evolution from spongy network structure to porous solid nanoparticle when change the calcinations temperature. The spongy sample shows good adsorption of small organ molecular and photo-inactivity. 2. Experimental Anatase TiO2 powders were synthesized by a modified EISA synthesis and a post microwave-assisted treatment [12,13]. In a typical synthesis, tri-block copolymer surfactant P123 was dissolved into a diluted hydrochloric acid (HCl)–ethanol (EtOH) solution and stirred for 30 min, the resultant transparent solution was labeled as A; at the same time, titanium tetraethoxide (TBOT) was dropped into diluted HCl–EtOH solution, and the demonized water was added dropwise after
X. Jia et al. / Materials Letters 62 (2008) 1896–1898
15 min vigorous stirring, the resultant light yellow solution was labeled as B. Then, solution B was added into A and stirred 30 min, a transparent sol with molar composition TBOT/P123/ HCl/H2O/EtOH = 1:0.002:4:8:30 was resulted. After keeping stationary for 30 min, the stock solution was transferred into a petri dish, and crack-free membranes were obtained after aged at 40 °C for 7 days in air. The as-prepared membranes were collected and transferred into a microwave oven (Glanz WP800L23-3), a self-propagation combustion was ignited at once when fired under high-power microwave. Lower temperature calcinations were treated at 360 °C with heating rate 2.5 °C/min and held the temperature for 3.5 h, higher temperature calcination was treated at 400 °C for 3.5 h with heating rate 20 °C/min. The crystalline structure was investigated by X-ray diffraction (XRD) on a D/max-ra X-ray diffractometer with Cu Kα radiation (λ = 0.15418 nm) and graphite monochromator. The morphologies were studied on a TEM-100X transition electron microscope. Brunauer–Emett–Teller (BET) method was used for the specific surface area investigation on ST-08A metering
1897
system. The photocatalysis was carried on self-designed equipment; 40 W/220 V UV lamp (365 nm) was used as luminous source and methyl orange as reactant. 3. Results and discussion Anatase TiO2 with morphologies from spongy network structure to porous nanoparticles was synthesized by a modified EISA method and a microwave-assisted combustion treatment. TEM photographs of sample calcined at 360 °C and 400 °C were shown in Fig. 1(a, b, c) and Fig. 1(d, e, f) respectively. In lower temperature calcinations samples (Fig. 1(a, b, c)), there showed the spongy network structure and large pores. Unfortunately, the spongy network texture was degenerated into porous nanoparticles when sintered under higher temperature (Fig. 1(e, f)). In higher resolution photograph (Fig. 1(c)) there showed some build-in pores, we supposed that the smaller pores merge into a larger one (Fig. 1(d)) when elevated the calcinations temperature. The selected area electron diffraction (SAED) image of the lower temperature calcinations samples was shown in the insert of Fig. 1 (a), therein unclearly diffraction halos were shown indicating poor crystallization. The detail image (Fig. 1(f)) of solid nanoparticles in
Fig. 1. TEM photographs of the sample calcined at 360 °C (a)–(c) and 400 °C (d)–(f). Insert images of (a) and (e) are selected area electron diffraction (SAED) patterns of sample calcined at 360 °C and 400 °C respectively. (Scale bar in all photographs is 100 nm).
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X. Jia et al. / Materials Letters 62 (2008) 1896–1898
texture would effectively diminish the probability of organ rejection that often happened during the tissue and organ transplantation. So, we considered that the spongy network structure TiO2 in our study might find use as biomimetic material.
4. Conclusions
Fig. 2. Wide-angle XRD patterns of the sample calcined at 360 °C (a) and 400 °C (b).
Fig. 1(d, e) indicated loose texture of the nanoparticles. The clearly diffraction rings in the insert of Fig. 1(e) indicated that the loose texture was well-crystallized (Fig. 1(e)), this was different with the normal compact nanoparticle morphology without the using of surfactant in the synthesis, indicated that the surfactant plays roles in the formation of the nanomorphologies. In a word, the lower temperature calcinations sample showed spongy network structure but poor-crystallized; and the higher temperature sample showed loose texture and well-crystallized. The wide-angle XRD patterns of sample calcined at 360 °C and 400 °C were shown in Fig. 2. The sample calcined at 400 °C showed sharp and broad peak, indicating well-crystallized and small crystalline size. The particles diameter of sample calculated according the halfwidth at the full maximum (HWFM) of (101) peak was 8.0 nm, and consistent well with large specific area of the sample (120 m2 g− 1). Comparatively, the sample calcined at 360 °C showed a broad halo, indicated that TiO2 nanocrystalline is smaller and macroscopic amorphous. The lower temperature calcination sample had larger specific area (275 m2 g− 1) than higher one. The photocatalysis was performed on self-designed equipment. The results showed that the sample calcined at 360 °C is photo-inactive; this was consistent well with the amorphous and poor-crystallized structure. The sample calcined at 400 °C showed good photocatalysis activity but weaker than the commercial P25. We supposed that the wellcrystallized mixed crystalline structure (75% anatase and 25% rutile) of P25 would be responsible for the photocatalysis superiority, although our sample calcined at 400 °C has larger specific areas (P25 is 50 m2 g− 1) and also good crystallized. The UV spectrums of the sample calcined at 360 °C and 400 °C showed large red shift than commercial P25, this was consistent with the amorphous structure of sample calcined at 360 °C and smaller crystalline size of sample calcined at 400 °C. The larger red shift of our sample than commercial P25 would be another reason for lower photocatalytic activity. Interestingly, larger methyl orange adsorption amount was observed in our sample calcined at 360 °C (1.75 mg g− 1) than the commercial P25 (0.5 mg/g) in our photocatalysis experiment, this was consistent with the larger specific area and amorphous spongy network structure of our sample, indicating a biomimetic usage. It has been demonstrated that nanocrystalline TiO2 is a potential candidate as an implantation material for its good mechanical property, nontoxicity and compatibility with organ and tissue. By forming an organic–inorganic interpenetrating network structures, TiO2 with spongy network structure would be more favorable to serve as the implantation material for human organ and tissue, for the special
In the study, nanomorphological anatase TiO2 from spongy network structure to porous nanoparticles was synthesized by a modified EISA method and a post microwave-assisted combustion treatment. The TEM studies showed that the spongy network structure formed at lower calcined temperature (360 °C) would partially collapsed into nanoparticles when elevated the calcination temperature (400 °C). The lower temperature calcination sample showed larger BET specific surface area (275 m2 g− 1) than higher sample (120 m2 g− 1). The photocatalysis investigation showed that the lower calcinations sample is photo-inactive and large adsorption of methyl orange. The spongy network structure, large organ molecular adsorption ability and photo-inactivity indicated that the material may find use as biomimetic material. Acknowledgement Thanks to the support from the Shandong Province Science Foundation under Award No. Y2002F20 and No. Y2003F02. We are grateful to Professor Jinshui Yao, Yuqing Chen, Suwen Li and Jianxing Shen for helpful discussions and technical assistance. References [1] M.R. Hoffmann, S.T. Martin, W. Choi, D.W. Bahnemann, Chem. Rev. 95 (1995) 69–96. [2] M. Kunst, T. Moehl, F. Wunsch, H. Tributsch, Superlattice Microst. 39 (2006) 376–380. [3] S.M. Karvinen, Ind. Eng. Chem. Res. 42 (2003) 1035–1043. [4] J. Chen, S.L. Li, Z.L. Tao, Y.T. Shen, C.X. Cui, J. Am. Chem. Soc. 125 (2003) 5284–5285. [5] S. Rana, J. Rawat, M.M. Sorensson, R.D. Misra, Acta Biomater. 2 (2006) 421–432. [6] G.K. Mor, K. Shankar, M. Paulose, O.K. Varghese, C.A. Grimes, Nano Lett. 5 (2005) 191–195. [7] J.H. Park, S. Kim, A.J. Bard, Nano Lett. 6 (2006) 24–28. [8] N. Popovicia, E. Jimeneza, R.C. da Silvab, W.R. Branfordc, L.F. Cohenc, O. Condea, J. Non-Cryst. Solids 352 (2006) 1486–1489. [9] S.H. Toma, J.A. Bonacin, K. Araki, H.E. Toma, Surf. Sci. 600 (2006) 4591–4597. [10] M. Alvaro, C. Aprile, M. Benitez, E. Carbonell, H. Garcia, J. Phys. Chem., B 110 (2006) 6661–6665. [11] K.L. Frindell, J. Tang, J.H. Harreld, G.D. Stucky, Chem. Mater. 16 (2004) 3524–3532. [12] D. Zhao, P. Yang, N. Melosh, J. Feng, B.F. Chmelka, G.D. Stucky, Adv. Mater. 10 (1998) 1380–1385. [13] P. Yang, D. Zhao, D.I. Margolese, B.F. Chmelka, G.D. Stucky, Nature 396 (1998) 152–155. [14] R. Gedye, F. Smith, K. Westaway, A. Humera, L. Baldisera, L. Laberge, et al., Tetrahedron Lett. 27 (1986) 279–282. [15] J.C. Yu, X. Hu, Q. Li, L. Zhang, Chem. Commun. (2005) 2704–2706. [16] J.W. Mitchell, R.A. Holland, Mater. Lett. 60 (2006) 1524–1526. [17] M.N. Nadagouda, R.S. Varma, Smart Mater. Struct. 15 (2006) 1260–1265.