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Preparation and adsorption properties of the biomimetic gama-alumina
Materials Letters 157 (2015) 67–69
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Preparation and adsorption properties of the biomimetic gamaalumina Yunhui Wang a, Qinglian Wei a,n, Yongmin Huang a,b a b
State Key Laboratory of Chemical Engineering and Department of Chemistry, East China University of Science and Technology, Shanghai 200237, PR China Shanghai Engineering Research Center of Space Engine, Shanghai Institute of Space Propulsion, Shanghai 201112, PR China
art ic l e i nf o
a b s t r a c t
Article history: Received 17 February 2015 Received in revised form 22 April 2015 Accepted 23 May 2015 Available online 27 May 2015
Biomimetic gama-alumina was prepared by using broadleaf Liriope leaf as template. The surface acidity of the sample was measured and the adsorption experiments were carried out. The results indicated that the obtained gama-alumina inherited the morphology and microstructure of leaf template and showed weak surface acidity. Therefore, the as-prepared alumina exhibited good adsorption performance for acid fuchsin, but bad adsorption toward alkaline methyl orange. After acid-modifying, the sample showed strong surface acidity and displayed good adsorption performance toward alkaline methyl orange. These results demonstrated that the surface acidity-alkalinity of alumina determined its adsorption performance and selectivity for organic compounds. & 2015 Elsevier B.V. All rights reserved.
Keywords: Biomimetic Gama-alumina Porous materials Surface acidity Adsorption
1. Introduction Activated alumina is widely used as catalyst support or adsorbent owing to its large specific surface area, particular channel and variable surface acidity/basicity [1–6]. At present, many methods for the preparation of porous alumina have been reported [7,8]. In recent years, researchers have paid much attention towards hierarchical porous materials in order to fulfill the demand of multifunctional materials. To this end, biomimetic synthetic strategy on the basis of biomineralization concept and mechanism has been developed and widely applied to synthesize functional materials with hierarchical pore structure. Compared with conventional methods of materials production, biomimetic approach is facile, environmentally benign and economical [9,10]. Moreover, because biological organisms possess multi-level and multi-dimensional structures with specific functionalities developed for adaptation to environmental conditions, the obtained bionic materials by replicating endow with unique structural and surface properties [11], which is difficult to get by conventional methods [12]. Up to now, some biomass such as silk [13], butterfly wings [14], Eggshell membrane [15], sisal fibers [16] and even plant skins [17], etc. have been used as biological templates for the preparation of biomorphic porous alumina and metal oxides. Among n
Corresponding author. Fax: þ 86 21 64250924. E-mail address: [email protected] (Q. Wei).
http://dx.doi.org/10.1016/j.matlet.2015.05.119 0167-577X/& 2015 Elsevier B.V. All rights reserved.
various bio-templates, the green leaves, which are diversiform and easy to get, are the most promising candidate for the preparation of hierarchical pore materials. The biomorphic hierarchical alumina materials can be expected to find better application prospect. Thus, in this paper, biomimetic method was described to prepare biomorphic alumina. The surface property of the obtained alumina was investigated, and the adsorption performance was evaluated by adsorbing acid fuchsin and alkaline methyl orange from water solution.
2. Experiment 2.1. Alumina preparation Fresh leaves were cleaned ultrasonically with deionized water, impregnated into aqueous-ethanol solution (50%, V/V) of pH ¼3 (adjusted with 1 mol L 1 hydrochloric acid) for 24 h, and washed with deionized water to remove the residual hydrochloric acid. Then, the pretreated leaves were soaked into Al(NO3)3 (1 mol L 1) aqueous solution at 40 °C for 48 h, and dried at 60 °C. Finally, the biomimetic alumina was obtained by calcining the Al3 þ -loaded leaves at 800 °C for 2 h in the air. The acid-modified alumina was obtained by immersing the as-prepared alumina in pH ¼ 5 aqueous solution adjusted by 1 mol L 1 hydrochloric acid at room temperature, and drying at 60 °C. All chemicals were of analytical grade and used without further purification.
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2.2. Characterization SEM micrographs were obtained on Hitachi SU1510 scanning electron microscope. XRD patterns were collected by Bruker D8 X-ray diffractometer using Cu-Kα (λ ¼0.154056 nm) radiation. UV– vis spectra were obtained on a Shimadzu UV-2450 UV–vis spectrophotometer. NH3-TPD was carried out in a conventional flow system equipped with a thermal conductivity detector (TCD). 2.3. Adsorption tests
Fig. 2. (A) XRD and (B) NH3-TPD curves of (1) the as-prepared alumina, (2) the acid-modified alumina.
0.02 g as-prepared alumina was added to 10 mL acid fuchsin aqueous solution (40 mg/L) under stirring at room temperature. For the adsorption of methyl orange (10 mg/L, 10 mL), the asprepared alumina (0.02 g) and the acid-modified alumina (0.02 g) were used as absorbent, respectively. UV–vis spectra recorded the absorption process.
3. Results and discussion Dried broadleaf Liriope leaf template displays characteristics of typical parallel venation with obvious main veins (Fig. 1A). Fig. 1 (B–D) shows the SEM images of the as-prepared biomimetic alumina. Obviously, the obtained sample also exhibits the parallel venation characteristics with a vein interval of 280 μm (Fig. 1C). Between the veins, many micron-sheets arranged in perpendicular to the vein are observed to form large pore structure with different morphologies and sizes, which are the products of replicating mesophyll tissue. Fig. 1D shows another typical structure in the obtained samples, which are parallel arrangement channels with pore diameter between 2 and 8 μm. These porous channels are the results of duplicating the vascular bundles. Therefore, the biomimetic alumina with hierarchical structure is obtained by inheriting the microscopic structure of the leaves. In addition, acid modification does not change the morphology and structure of the asprepared alumina (shown in Fig. 1E and F). The phase of the biomimetic alumina material is identified by XRD analysis. The XRD spectra of samples (shown in Fig. 2A) display three well-defined diffraction peaks at 67 °, 45.8 °, 37.6 °, which can be indexed as (440), (400) and (311) planes in cubic phase of gama-alumina according to JCPDS card No. 10-0425 [18]. The crystalline phase of the as-prepared alumina does not change after acid-modifying. In addition, the strong and sharp diffraction
peaks indicate the good crystallinity of the product. The surface acidity is also an important characteristic parameter of the alumina for adsorption application, which can be evaluated by the NH3-TPD curve. As shown in Fig. 2B, it is obvious that both the as-prepared alumina and acid-modified alumina exist more weak acid sites on the surface because of the wider and higher peak for NH3 desorption at the lower temperature. Compared with Fig. 2B(1) and (2), alumina surface strong acid sites and total acidity increase after acid modification. Thus, the NH3-TPD results confirm that the as-prepared biomimetic alumina displays a very weak surface acidity while the acid-modified samples present a stronger surface acidity. Acid fuchsin and methyl orange, which are used as commercial colorants in the dyeing industry, are chosen as the model substrates. Adsorption maxima of acid fuchsin (465 nm) and methyl orange (495 nm) is monitored to evaluate the removal efficiency of sorbent. Fig. 3A presents the time-dependent UV–vis absorption spectra for an aqueous solution of acid fuchsin, when the as-prepared biomimetic alumina is used as the adsorbent. The corresponding color changes and decolorization rate are outlined in Fig. 3 B. A series of rapid color changes from red to colorless indicate an excellent adsorption performance of as-synthesized alumina toward the acid dye. When the initial concentration of acid fuchsin solution is 40 mg/L, the alumina can remove about 96% of acid fuchsin after 4 min without any additives at room temperature, with a removal capacity of 19.4 mg/g. However, spectra with no damping of adsorption are observed for the alkaline methyl orange (Fig. 3 C(1) and (2)) in the presence of as-prepared alumina, indicating no interaction between the alkaline dye molecules and the as-prepared alumina. On the contrary, the adsorption capacity and removal efficiency of the
Fig. 1. SEM images of the dried Liriope leaf (A), the as-prepared alumina (B–D), and the acid-modified alumina (E, F).
Y. Wang et al. / Materials Letters 157 (2015) 67–69
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the alumina surface acidity influences its adsorption properties and selectivity for the organic matter.
4. Conclusion The alumina with biomimetic structure can be prepared from the leaf template and shows very weak acidity surface, and thus has a good adsorption affinity to acid fuchsin but no adsorption for methyl orange. While the acid-modified alumina displays well adsorption performance towards methyl orange. This study can offer experimental reference for the adsorption performance and selectivity of the alumina for the organic matters.
Acknowledgments
Fig. 3. (A) Absorption spectra of acid fuchsin (40 mg/L, 10 mL) in the presence of as-prepared alumina at time intervals of 0, 0.5, 1, 2, 4, 8, and 12 min, respectively; (B) Adsorption rate of acid fuchsin on alumina, the inset shows the corresponding color change after different adsorption time; (C) Absorption spectra of methyl orange solution after 20 min: (1) before adsorption, (2) after adsorption by the asprepared alumina, (3) after adsorption by the acid-modified alumina; and (D) Optical photographs of the solution corresponding to (C).
as-prepared alumina toward the alkaline methyl orange are significantly enhanced after the acid treatment. Color change of the methyl orange could be seen in the addition of acid-treated adsorbent mass (Fig. 3D(3)). Furthermore, it can be observed that 80% of the methyl orange is removed within 2 min. This result demonstrates that the introduction of H þ into alumina can efficiently increase the alumina surface acidity, and then enhance its adsorption ability toward alkaline methyl orange. The adsorption performance of alumina materials towards the chosen dyes may be explained by considering different dye molecule structures and the surface charge properties of gama-alumina before and after the acid treatment. It is well known that the surface of gama-alumina, which has a point of zero charge (pHZPC) value of 7.9, is positively charged in neutral environments [19]. The negatively charged dye molecules are strongly attracted towards the adsorbent surface. Thus, electrostatic force of attraction between the positively charged gama-alumina and negatively charged dye molecules is responsible for the high adsorption capacity. Acid fuchsin itself carries negative charges in the solution, which leads to strong interaction with weak acidic sites on the asprepared alumina surface. But, for methyl orange, the lone pair electrons on the molecular N atom make the methyl orange possess strong nucleophilic ability, which results in more easily adsorbing on strong acidic alumina surface. Hence one can see that
This work was partly supported by the Open Project of State Key Laboratory of Chemical Engineering (SKL-ChE).
References [1] W.Q. Cai, J.G. Yu, C. Anand, A. Vinu, M. Jaroniec, Chem. Mater. 23 (2011) 1147–1157. [2] Z.R. Zhang, T.J. Pinnavaia, Langmuir 26 (2010) 10063–10067. [3] M. Trueba, S.P. Trasatti, Eur. J. Inorg. Chem. (2005) 3393–3403. [4] S.Y. Bhattacharyya, A. Gedanken, J. Phys. Chem. C 112 (2008) 13156–13162. [5] S.M. Morris, P.F. Fulvio, M.J. Jaroniec, Am. Chem. Soc. 130 (2008) 15210–15216. [6] S. Zanganeh, A. Kajbafvala, N. Zanganeh, M.S. Mohajerani, A. Lak, M.R. Bayati, Appl. Phys. A 99 (2010) 317–321. [7] A.P. Su, Y. Zhou, Y.H. Yao, C.M. Yang, H. Du, Microporous Mesoporous Mater. 159 (2012) 36–41. [8] Q. Liu, A.Q. Wang, X.D. Wang, T. Zhang, Chem. Mater. 18 (2006) 5153–5155. [9] S.M. Zhu, D. Zhang, Z.Q. Li, H. Furukawa, Z.X. Chen, Langmuir 24 (2008) 6292–6299. [10] X.F. Li, T.X. Fan, H. Zhou, S.K. Chow, W. Zhang, D. Zhang, Q.X. Guo, H. Ogawa, Adv. Funct. Mater. 19 (2009) 45–56. [11] T.X. Fan, S.K. Chow, D. Zhang, Prog. Mater. Sci. 54 (2009) 542–659. [12] T.X. Fan, S.K. Chow, D. Zhang, Prog. Mater. Sci. 54 (2009) 542–659. [13] T.C. Wang, S. Kong, Y. Jia, L.J. Chang, D.S. Xiong, Int. J. Appl. Ceram. Technol. 10 (2013) 285–292. [14] Q.Q. Yang, S.M. Zhu, W.H. Peng, C. Yin, W.L. Wang, J.J. Gu, W. Zhang, J. Ma, T. Deng, C.L. Feng, D. Zhang, ACS Nano 7 (2013) 4911–4918. [15] D.H. Dong, Y.Z. Wu, X.Y. Zhang, J.F. Yao, Y. Huang, D. Li, C.Z. Li, H.T.J. Wang, Mater. Chem. 21 (2011) 1028–1032. [16] M. Benítez-Guerrero, L.A. Pérez-Maqueda, P.E. Sánchez-Jiménez, J. PascualCosp, Microporous Mesoporous Mater. 185 (2014) 167–178. [17] Y.C. Miao, Z.B. Zhai, J. He, B. Li, J.J. Li, J.Q. Wang, Mater. Sci. Eng. C 30 (2010) 839–846. [18] J.R. Ge, K.J. Deng, W.Q. Cai, J.G. Yu, X.Q. Liu, J.B. Zhou, J. Colloid Interface Sci. 401 (2013) 34–39. [19] W. Jiang, S. Ghosh, L. Song, R.W. Vachet, B.S. Xing, Colloids Surf. B 102 (2013) 292–299.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Preparation and adsorption properties of the biomimetic gamaalumina Yunhui Wang a, Qinglian Wei a,n, Yongmin Huang a,b a b
State Key Laboratory of Chemical Engineering and Department of Chemistry, East China University of Science and Technology, Shanghai 200237, PR China Shanghai Engineering Research Center of Space Engine, Shanghai Institute of Space Propulsion, Shanghai 201112, PR China
art ic l e i nf o
a b s t r a c t
Article history: Received 17 February 2015 Received in revised form 22 April 2015 Accepted 23 May 2015 Available online 27 May 2015
Biomimetic gama-alumina was prepared by using broadleaf Liriope leaf as template. The surface acidity of the sample was measured and the adsorption experiments were carried out. The results indicated that the obtained gama-alumina inherited the morphology and microstructure of leaf template and showed weak surface acidity. Therefore, the as-prepared alumina exhibited good adsorption performance for acid fuchsin, but bad adsorption toward alkaline methyl orange. After acid-modifying, the sample showed strong surface acidity and displayed good adsorption performance toward alkaline methyl orange. These results demonstrated that the surface acidity-alkalinity of alumina determined its adsorption performance and selectivity for organic compounds. & 2015 Elsevier B.V. All rights reserved.
Keywords: Biomimetic Gama-alumina Porous materials Surface acidity Adsorption
1. Introduction Activated alumina is widely used as catalyst support or adsorbent owing to its large specific surface area, particular channel and variable surface acidity/basicity [1–6]. At present, many methods for the preparation of porous alumina have been reported [7,8]. In recent years, researchers have paid much attention towards hierarchical porous materials in order to fulfill the demand of multifunctional materials. To this end, biomimetic synthetic strategy on the basis of biomineralization concept and mechanism has been developed and widely applied to synthesize functional materials with hierarchical pore structure. Compared with conventional methods of materials production, biomimetic approach is facile, environmentally benign and economical [9,10]. Moreover, because biological organisms possess multi-level and multi-dimensional structures with specific functionalities developed for adaptation to environmental conditions, the obtained bionic materials by replicating endow with unique structural and surface properties [11], which is difficult to get by conventional methods [12]. Up to now, some biomass such as silk [13], butterfly wings [14], Eggshell membrane [15], sisal fibers [16] and even plant skins [17], etc. have been used as biological templates for the preparation of biomorphic porous alumina and metal oxides. Among n
Corresponding author. Fax: þ 86 21 64250924. E-mail address: [email protected] (Q. Wei).
http://dx.doi.org/10.1016/j.matlet.2015.05.119 0167-577X/& 2015 Elsevier B.V. All rights reserved.
various bio-templates, the green leaves, which are diversiform and easy to get, are the most promising candidate for the preparation of hierarchical pore materials. The biomorphic hierarchical alumina materials can be expected to find better application prospect. Thus, in this paper, biomimetic method was described to prepare biomorphic alumina. The surface property of the obtained alumina was investigated, and the adsorption performance was evaluated by adsorbing acid fuchsin and alkaline methyl orange from water solution.
2. Experiment 2.1. Alumina preparation Fresh leaves were cleaned ultrasonically with deionized water, impregnated into aqueous-ethanol solution (50%, V/V) of pH ¼3 (adjusted with 1 mol L 1 hydrochloric acid) for 24 h, and washed with deionized water to remove the residual hydrochloric acid. Then, the pretreated leaves were soaked into Al(NO3)3 (1 mol L 1) aqueous solution at 40 °C for 48 h, and dried at 60 °C. Finally, the biomimetic alumina was obtained by calcining the Al3 þ -loaded leaves at 800 °C for 2 h in the air. The acid-modified alumina was obtained by immersing the as-prepared alumina in pH ¼ 5 aqueous solution adjusted by 1 mol L 1 hydrochloric acid at room temperature, and drying at 60 °C. All chemicals were of analytical grade and used without further purification.
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2.2. Characterization SEM micrographs were obtained on Hitachi SU1510 scanning electron microscope. XRD patterns were collected by Bruker D8 X-ray diffractometer using Cu-Kα (λ ¼0.154056 nm) radiation. UV– vis spectra were obtained on a Shimadzu UV-2450 UV–vis spectrophotometer. NH3-TPD was carried out in a conventional flow system equipped with a thermal conductivity detector (TCD). 2.3. Adsorption tests
Fig. 2. (A) XRD and (B) NH3-TPD curves of (1) the as-prepared alumina, (2) the acid-modified alumina.
0.02 g as-prepared alumina was added to 10 mL acid fuchsin aqueous solution (40 mg/L) under stirring at room temperature. For the adsorption of methyl orange (10 mg/L, 10 mL), the asprepared alumina (0.02 g) and the acid-modified alumina (0.02 g) were used as absorbent, respectively. UV–vis spectra recorded the absorption process.
3. Results and discussion Dried broadleaf Liriope leaf template displays characteristics of typical parallel venation with obvious main veins (Fig. 1A). Fig. 1 (B–D) shows the SEM images of the as-prepared biomimetic alumina. Obviously, the obtained sample also exhibits the parallel venation characteristics with a vein interval of 280 μm (Fig. 1C). Between the veins, many micron-sheets arranged in perpendicular to the vein are observed to form large pore structure with different morphologies and sizes, which are the products of replicating mesophyll tissue. Fig. 1D shows another typical structure in the obtained samples, which are parallel arrangement channels with pore diameter between 2 and 8 μm. These porous channels are the results of duplicating the vascular bundles. Therefore, the biomimetic alumina with hierarchical structure is obtained by inheriting the microscopic structure of the leaves. In addition, acid modification does not change the morphology and structure of the asprepared alumina (shown in Fig. 1E and F). The phase of the biomimetic alumina material is identified by XRD analysis. The XRD spectra of samples (shown in Fig. 2A) display three well-defined diffraction peaks at 67 °, 45.8 °, 37.6 °, which can be indexed as (440), (400) and (311) planes in cubic phase of gama-alumina according to JCPDS card No. 10-0425 [18]. The crystalline phase of the as-prepared alumina does not change after acid-modifying. In addition, the strong and sharp diffraction
peaks indicate the good crystallinity of the product. The surface acidity is also an important characteristic parameter of the alumina for adsorption application, which can be evaluated by the NH3-TPD curve. As shown in Fig. 2B, it is obvious that both the as-prepared alumina and acid-modified alumina exist more weak acid sites on the surface because of the wider and higher peak for NH3 desorption at the lower temperature. Compared with Fig. 2B(1) and (2), alumina surface strong acid sites and total acidity increase after acid modification. Thus, the NH3-TPD results confirm that the as-prepared biomimetic alumina displays a very weak surface acidity while the acid-modified samples present a stronger surface acidity. Acid fuchsin and methyl orange, which are used as commercial colorants in the dyeing industry, are chosen as the model substrates. Adsorption maxima of acid fuchsin (465 nm) and methyl orange (495 nm) is monitored to evaluate the removal efficiency of sorbent. Fig. 3A presents the time-dependent UV–vis absorption spectra for an aqueous solution of acid fuchsin, when the as-prepared biomimetic alumina is used as the adsorbent. The corresponding color changes and decolorization rate are outlined in Fig. 3 B. A series of rapid color changes from red to colorless indicate an excellent adsorption performance of as-synthesized alumina toward the acid dye. When the initial concentration of acid fuchsin solution is 40 mg/L, the alumina can remove about 96% of acid fuchsin after 4 min without any additives at room temperature, with a removal capacity of 19.4 mg/g. However, spectra with no damping of adsorption are observed for the alkaline methyl orange (Fig. 3 C(1) and (2)) in the presence of as-prepared alumina, indicating no interaction between the alkaline dye molecules and the as-prepared alumina. On the contrary, the adsorption capacity and removal efficiency of the
Fig. 1. SEM images of the dried Liriope leaf (A), the as-prepared alumina (B–D), and the acid-modified alumina (E, F).
Y. Wang et al. / Materials Letters 157 (2015) 67–69
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the alumina surface acidity influences its adsorption properties and selectivity for the organic matter.
4. Conclusion The alumina with biomimetic structure can be prepared from the leaf template and shows very weak acidity surface, and thus has a good adsorption affinity to acid fuchsin but no adsorption for methyl orange. While the acid-modified alumina displays well adsorption performance towards methyl orange. This study can offer experimental reference for the adsorption performance and selectivity of the alumina for the organic matters.
Acknowledgments
Fig. 3. (A) Absorption spectra of acid fuchsin (40 mg/L, 10 mL) in the presence of as-prepared alumina at time intervals of 0, 0.5, 1, 2, 4, 8, and 12 min, respectively; (B) Adsorption rate of acid fuchsin on alumina, the inset shows the corresponding color change after different adsorption time; (C) Absorption spectra of methyl orange solution after 20 min: (1) before adsorption, (2) after adsorption by the asprepared alumina, (3) after adsorption by the acid-modified alumina; and (D) Optical photographs of the solution corresponding to (C).
as-prepared alumina toward the alkaline methyl orange are significantly enhanced after the acid treatment. Color change of the methyl orange could be seen in the addition of acid-treated adsorbent mass (Fig. 3D(3)). Furthermore, it can be observed that 80% of the methyl orange is removed within 2 min. This result demonstrates that the introduction of H þ into alumina can efficiently increase the alumina surface acidity, and then enhance its adsorption ability toward alkaline methyl orange. The adsorption performance of alumina materials towards the chosen dyes may be explained by considering different dye molecule structures and the surface charge properties of gama-alumina before and after the acid treatment. It is well known that the surface of gama-alumina, which has a point of zero charge (pHZPC) value of 7.9, is positively charged in neutral environments [19]. The negatively charged dye molecules are strongly attracted towards the adsorbent surface. Thus, electrostatic force of attraction between the positively charged gama-alumina and negatively charged dye molecules is responsible for the high adsorption capacity. Acid fuchsin itself carries negative charges in the solution, which leads to strong interaction with weak acidic sites on the asprepared alumina surface. But, for methyl orange, the lone pair electrons on the molecular N atom make the methyl orange possess strong nucleophilic ability, which results in more easily adsorbing on strong acidic alumina surface. Hence one can see that
This work was partly supported by the Open Project of State Key Laboratory of Chemical Engineering (SKL-ChE).
References [1] W.Q. Cai, J.G. Yu, C. Anand, A. Vinu, M. Jaroniec, Chem. Mater. 23 (2011) 1147–1157. [2] Z.R. Zhang, T.J. Pinnavaia, Langmuir 26 (2010) 10063–10067. [3] M. Trueba, S.P. Trasatti, Eur. J. Inorg. Chem. (2005) 3393–3403. [4] S.Y. Bhattacharyya, A. Gedanken, J. Phys. Chem. C 112 (2008) 13156–13162. [5] S.M. Morris, P.F. Fulvio, M.J. Jaroniec, Am. Chem. Soc. 130 (2008) 15210–15216. [6] S. Zanganeh, A. Kajbafvala, N. Zanganeh, M.S. Mohajerani, A. Lak, M.R. Bayati, Appl. Phys. A 99 (2010) 317–321. [7] A.P. Su, Y. Zhou, Y.H. Yao, C.M. Yang, H. Du, Microporous Mesoporous Mater. 159 (2012) 36–41. [8] Q. Liu, A.Q. Wang, X.D. Wang, T. Zhang, Chem. Mater. 18 (2006) 5153–5155. [9] S.M. Zhu, D. Zhang, Z.Q. Li, H. Furukawa, Z.X. Chen, Langmuir 24 (2008) 6292–6299. [10] X.F. Li, T.X. Fan, H. Zhou, S.K. Chow, W. Zhang, D. Zhang, Q.X. Guo, H. Ogawa, Adv. Funct. Mater. 19 (2009) 45–56. [11] T.X. Fan, S.K. Chow, D. Zhang, Prog. Mater. Sci. 54 (2009) 542–659. [12] T.X. Fan, S.K. Chow, D. Zhang, Prog. Mater. Sci. 54 (2009) 542–659. [13] T.C. Wang, S. Kong, Y. Jia, L.J. Chang, D.S. Xiong, Int. J. Appl. Ceram. Technol. 10 (2013) 285–292. [14] Q.Q. Yang, S.M. Zhu, W.H. Peng, C. Yin, W.L. Wang, J.J. Gu, W. Zhang, J. Ma, T. Deng, C.L. Feng, D. Zhang, ACS Nano 7 (2013) 4911–4918. [15] D.H. Dong, Y.Z. Wu, X.Y. Zhang, J.F. Yao, Y. Huang, D. Li, C.Z. Li, H.T.J. Wang, Mater. Chem. 21 (2011) 1028–1032. [16] M. Benítez-Guerrero, L.A. Pérez-Maqueda, P.E. Sánchez-Jiménez, J. PascualCosp, Microporous Mesoporous Mater. 185 (2014) 167–178. [17] Y.C. Miao, Z.B. Zhai, J. He, B. Li, J.J. Li, J.Q. Wang, Mater. Sci. Eng. C 30 (2010) 839–846. [18] J.R. Ge, K.J. Deng, W.Q. Cai, J.G. Yu, X.Q. Liu, J.B. Zhou, J. Colloid Interface Sci. 401 (2013) 34–39. [19] W. Jiang, S. Ghosh, L. Song, R.W. Vachet, B.S. Xing, Colloids Surf. B 102 (2013) 292–299.