- Email: [email protected]
Effect of tourmaline addition on the structure of silica hollow microspheres prepared by a novel template method
Accepted Manuscript Effect of tourmaline mineral materials on the structure of silicon dioxide hollow microspheres prepared via a novel template Fei Wang, Hui Zhang, Jinsheng Liang, Dan Feng, Qingguo Tang, Kaihua Yu, Zengyao Shang PII:
S0925-8388(16)32893-6
DOI:
10.1016/j.jallcom.2016.09.141
Reference:
JALCOM 38975
To appear in:
Journal of Alloys and Compounds
Received Date: 14 July 2016 Revised Date:
2 September 2016
Accepted Date: 13 September 2016
Please cite this article as: F. Wang, H. Zhang, J. Liang, D. Feng, Q. Tang, K. Yu, Z. Shang, Effect of tourmaline mineral materials on the structure of silicon dioxide hollow microspheres prepared via a novel template, Journal of Alloys and Compounds (2016), doi: 10.1016/j.jallcom.2016.09.141. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Effect of tourmaline mineral materials on the structure of silicon dioxide hollow microspheres prepared via a novel template Fei Wang1,2, , Hui Zhang1,2, Jinsheng Liang1,2, Dan Feng1,2, ﹡
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Qingguo Tang1,2, Kaihua Yu1,2, Zengyao Shang1,2 1
Institute of Power Source & Ecomaterials Science, Hebei University of Technology, 300130 Tianjin, China Key Laboratory of Special Functional Materials for Ecological Environment and Information, Hebei University of Technology, Ministry of Education, Tianjin 300130, China ﹡correspondence author: [email protected]
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Keywords: tourmaline; mineral materials; silicon dioxide; hollow microspheres; biological template
Introduction
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Abstract. In this article, the silica hollow microspheres were prepared through the sol-gel method, using conglobate synechocystis sp. as a novel biological template. The pretreated synechocystis sp. was implanted into the silica precursor, and then solidified into shell on the surface of synechocystis sp. template by means of condensation polymerization reaction along with base catalysts. Meanwhile, the tourmaline mineral materials for performance optimization were added into the silica precursor implanted with synechocystis sp. The effect of tourmaline mineral materials on the structure of silicon dioxide hollow microspheres was studied systematically. Experimental results showed that regular spherical silica hollow microspheres as prepared have average particle size of about 2µm and uniform shell-thickness of about 80 nm. The sol-gel process of TEOS could be accelerated by adding tourmaline, leading to the agglomeration degree decrease of silica hollow microspheres. The above phenomenon could be ascribed to enhancement of water molecules ionization due to spontaneous polarization and far-infrared properties of tourmaline mineral materials, which accelerates the hydrolysis-condensation rate of TEOS. At the same time, the ion concentration in solution was reduced by spontaneous polarization, and the compressed degree on diffused electric double layer was also decreased. The silica hollow microspheres as prepared exhibited regular hollow spherical structure, thus acting as a promising candidate in the field of thermal insulation materials.
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Due to the characteristics of low cost, high hardness, heat insulation and fire resistance etc., hollow glass microspheres have been researched by many scientists in the fields of highly selective catalyst or catalyst carrier, electrocatalysis, lithium battery, light filler, low dielectric constant materials, controlled drug transport and slow release, disease diagnosis and so on[1-7]. In recent years, the preparation method of hollow microspheres has gradually become the focus of attention, and the template method has become one of the important preparation methods. The disadvantages of the common hard and soft template method were toxic byproducts formation, high cost, and severe pollution during the production process [8-12]. Biological template method is a new method to prepare the special structure material using the microorganism as raw material, which overcomes the disadvantages of common hard and soft template methods. At present, biological template methods have been widely used in the preparation of hollow microspheres, and the biological templates often use natural organisms, including algae, pollen, bacteria, and viruses[13-15]. Cyanobacteria synechocystis has good roundness and strong dispersion, which is easy to obtain in the short term due to the simple training process and condition [16-20]. Tourmaline mineral materials as a kind of borate mineral have many unique properties [21-25]. Due to the characteristics of negative ions generation, far infrared emitting, permanent electrode effect and electrostatic fields 1
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formation, tourmaline mineral materials have been applied in many fields, including environmental protection [27], human health[28], chemical engineering [29], health care textile[30], electromagnetic shielding[31], and hardening agent materials [32]. Among them, the far-infrared emission and the spontaneous permanent electrode of tourmaline can play an important role in water activation, which could be applied to improve the structure of hollow microspheres in theory. However, to the authors’ knowledge, there is no report about the studies of the effects of tourmaline mineral materials on the structure of silicon dioxide hollow microspheres prepared by the biological template. In this study, the silica hollow microspheres were prepared by the sol-gel method, using conglobate synechocystis sp. as a novel biological template, and the effect of tourmaline mineral materials on the silicon dioxide hollow microspheres structure was also investigated.
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Synechocystis sp. was supplied by Freshwater Algae Culture Collection at the Institute of Hydrobiology. The tourmaline which is one of natural mineral materials was purchased from Hebei province of China. The compounding ingredients were supplied by Fengchuan and Bodi Chemical Group Co., Ltd. The preparation process of silicon dioxide hollow microspheres is as follows. The mother liquid of synechocystis medium was prepared, according to the BG11 (Blue-Green Medium) liquid medium formula. The mother liquid, deionized water and glassware used in the inoculation process of algal cells were treated by high temperature and pressure sterilization. The algae culture solution was formed by constant volume mixing mother liquid and deionized water after cooling, accordance to the BG11 medium ratio. Then the synechocystis was moved into the culture bottle, which was full of the algae culture solution. Finally, the culture bottle was put into the artificial climate incubator for 15 days at 30 oC with 2000lx of light intensity. Moreover, the light irradiation time was 12h, and the pH value was 8. After that, the cultivated synechocystis sp. liquid was prepared. On the above basis, the dehydrated synechocystis was obtained by many dehydration and centrifugation process, using 4 vol.% of formaldehyde solution and different concentration levels of ethanol solution. The tourmaline was broken into small powders with diameter of about 1~2 mm, and the powders were ball milled for 2.5 h at 1100 r/min. Then the ball milled powders were dried at 60 oC , and heated at 800 oC for
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3h [33-35]. The 3 ml TEOS and 10 ml anhydrous ethanol were mixed into solution A, and the solution B was formed by mixing 3 ml of concentrated ammonia water (27%), 10 ml of water and 9 ml anhydrous ethanol. The appropriate amount of treated synechocystis was added into the solution B, and the mixture was treated by ultrasonic wave for 2min, in order to make water and concentrated ammonia water adsorb quickly and evenly on the surface of the cell. Then the solution A was slowly added into the solution B in the stirring process, in order to make the formed silicon dioxide colloidal particles coated evenly on the surface of the algal cells. After that, 0.2 g of heat treated tourmaline was added into the mixed liquid. Then the mixture was stirred at room temperature for 36 h, and was aged at room temperature for 24 h. Then the solid phase was collected by centrifugation, washing and drying. Finally, the silicon dioxide hollow microspheres were prepared by calcination at 550 oC for 8 h. Scanning electron microscopy (S-4800, SEM, Hitachi Limited, Tokyo, Japan) was used to observe sample morphological features at an acceleration voltage of 3kVA, and the X-ray diffraction (XRD) analysis was performed on a Philips-DMAX-2500 with Cu Kα radiation. The Fourier transform infrared spectrum (FTIR) was performed on a BRUKER-80V made in Germany using KBr discs to monitor changes of functional groups during chemical modification. The microstructure of silicon dioxide hollow microspheres was analyzed by JEM-2010 TEM.
Results and discussion 2
ACCEPTED MANUSCRIPT The silica microspheres were prepared by using synechocystis of dehydration pretreatment as template with concentrated ammonia water as a catalytic agent. The effect of tourmaline addition on the prepared microspheres microstructure was shown in Fig.1.
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Fig.1 SEM images showing the microstructure of silicon dioxide hollow microspheres using base as catalyst (a) adding no tourmaline, (b) adding tourmaline
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From Fig.1(a), it can be seen that the microspheres maintained the regular spherical morphology of synechocystis bio templates in a large extent. After the preparation process of stirring, aging and calcination, a lot of spherical particles appeared on the surface and the surrounding of microspheres. The microspheres surface was uneven, and the average diameter was about 2µm. Among them, the point of the arrow was the damaged hole of a microsphere, which can be inferred that TEOS formed a shell reacted on the cell surface. Moreover, the dispersion and size uniformity of microspheres was low. On the other hand, we can see from Fig.1(b) that regular spherical silica hollow microspheres as prepared have average particle size of about 2µm. With alkali as the catalyst, the formation of sphere wall was arranged by the particles which closely connected by van der Waals’ force and hydrogen bond or chemical bond, and microspheres surface was rugged. Furthermore, it can be seen from the observation of samples collected by centrifugation after aging, in the same time, the silica microspheres yield of adding tourmaline sample was 50% higher than the case without adding tourmaline. From Fig.1(b), it also can be seen that the dispersion of samples were improved after adding tourmaline in the process. Moreover, we can see from the energy spectra (Fig.2) that the components of the samples are mainly composed by Si and O elements, which is consistent of silicon dioxide hollow microspheres.
Fig.2 Energy spectra of the sample as-prepared The TEM image of silicon dioxide hollow microspheres after adding tourmaline was shown in Fig.3.
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Fig.3. TEM image taken from silicon dioxide hollow microspheres after adding tourmaline
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It can be seen from the Fig.3 that the synechocystis cells were in normal growth stage, and the silica microspheres maintained the spherical morphology of the synechocystis. Bright-field TEM contrast has a nature of two dimensional projection of mass thickness accumulating along beam direction. A significant difference with light and dark in the microspheres can be found, indicating that the microspheres have a hollow structure. The arrow 1 points to the outer wall of the microsphere, and the arrow 2 points to the inner wall of the microsphere. It can be seen that the algae have been removed by calcination and the silica hollow microspheres have been prepared successfully. On the basis, the wall thickness of hollow microspheres is about 80nm, which is obtained by using digital micrograph software. Fig. 4 displays the XRD patterns from the silicon dioxide hollow microspheres using base as catalyst (a) adding no tourmaline, (b) adding tourmaline, respectively.
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Fig.4 XRD pattern of silicon dioxide hollow microspheres using base as catalyst (a) adding no tourmaline, (b) adding tourmaline It can be seen from Fig.4(a) that samples were amorphous state, which showed that the crystal of the sample 4
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could not be changed by calcination. From Fig.4(b), we can see that the mainly diffraction peaks were tourmaline (T), SiO2 (s), spinel (m) and iron oxide (f); the latter two were caused by the heating process at 800 oC. Moreover, the crystal plane indexes {hkl} of tourmaline characteristic peaks were (211), (220) and (051). However, the characteristic peak of SiO2 still existed, showing that adding tourmaline would not affect the hydrolysis condensation process of TEOS. In addition, the XRD diffraction peak of prepared silicon dioxide microspheres adding tourmaline was wider obviously, indicating the larger extent of amorphization. To further confirm the silicon dioxide microspheres structure, chemical characteristics of the different samples were monitored by FT-IR with the results shown in Fig. 5.
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Fig.5 FT-IR spectra of silicon dioxide hollow microspheres using base as catalyst (a) adding no tourmaline, (b) adding tourmaline
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In Fig.5, some absorption peaks between 400 and 600 cm-1 can be ascribed as Si-O stretching vibration, Si-O-Si symmetric stretching vibration, B-O deformation vibration and M-O stretching vibration of metal ions; some absorption peaks between 1000 and 1200 cm-1, between 1200 and 1450 cm-1, between 3250 and 3750 cm-1, and 1626 cm-1 can be labeled as Si-O-Si anti symmetric stretching vibration, B-O symmetric stretching vibration, O-H bond stretching vibration of structure water or adsorbed water and O-H bond bending vibration. Compared with silicon dioxide microspheres adding no tourmaline, Si-O-Si vibration peaks of silicon dioxide microspheres with tourmaline shift to lower wave number, which indicates the smaller group stability of silicon dioxide microspheres after adding tourmaline in the preparation process. The effect of tourmaline on the growth of silicon dioxide microspheres grown on the synechocystis with the alkaline catalyst condition is analyzed as follows. The hydrolysis reaction of positive ethyl silicate is the OHnucleophilic attack Si atom, and OH- plays a catalytic role. The H+ and OH- concentration in the water is increased by the spontaneous polarization properties of tourmaline, accelerating the hydrolysis condensation reaction and the aggregation of small colloidal particles on the surface of synechocystis. At the same time, the clusters of water molecules are reduced due to the far infrared emission of tourmaline, and the hydrolysis condensation reaction is accelerated due to the decrease of the resistance in the colloid diffusion process. Fig.6 shows the silicon dioxide hollow microspheres preparation process at alkali catalysts after adding heated tourmaline.
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Fig.6 Preparation diagram of silicon dioxide hollow microspheres at alkali catalysts after adding heated tourmaline
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From Fig.6, we can see that the OH- in the catalyst is adsorbed rapidly on the surface of synechocystis implanted into the solution B. After the addition of TEOS, a small amount of TEOS is combined with OH- on the surface of synechocystis, and then submicron particles generated by hydrolysis reaction are concluded to nucleus. Moreover, more submicron particles generated by the extracellular solution also form the nucleus with the increase of the addition amount of TEOS. The sub micro particles core is formed on the surface of the synechocystis by diffusion and collision, and the particles are grown up by the surface reaction and diffusion control mechanisms.
Conclusions
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In this work, the silica hollow microspheres were obtained using conglobate synechocystis sp. as a novel biological template, and the effect of tourmaline mineral materials on the structure of silicon dioxide hollow microspheres was studied systematically. The results showed that regular spherical silica hollow microspheres as prepared have average particle size of about 2µm and uniform shell-thickness of about 80 nm. A significant contrast difference of light and dark in the microspheres can be found in the TEM image, confirming that the microspheres have a hollow structure. The sol-gel process of TEOS could be accelerated by adding tourmaline, thus the agglomeration degree of silica hollow microspheres decreased. The reason for the above phenomenon was that the ionization of water molecules was enhanced by spontaneous polarization and far-infrared properties of tourmaline, and the hydrolysis-condensation rate of TEOS was accelerated. Meanwhile, the ion concentration in solution was reduced due to spontaneous polarization, and the compressed degree on diffused electric double layer was also reduced.
Acknowledgements
This research was financially supported by the National Natural Science Foundation of China (Grant no. 51404085), Key Technology R&D Program of Tianjin city (Grant no. 15ZCZDSF00030), China Postdoctoral Science Foundation (Grant no. 2015M571255), and Natural Science Foundation of Hebei province (Grant no. E2013202142). References [1] L. Renuka, K.S. Anantharaju, S.C. Sharma, H.P. Nagaswarupa, S.C. Prashantha, H. Nagabhushana, Y.S. Vidya, Journal of Alloys and Compounds. 672 (2016) 609-622. 6
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[2] S. S. Moosavi, P. Alizadeh, Materials Letters. 167 (2016) 98-101. [3] S. Bera, M. Pal, A. Naskar, S. Jana, Journal of Alloys and Compounds. 669(2016) 177-186. [4] B. Dong, J. Hao, T. Zhang, J. Lim, Sensors and Actuators B: Chemical. 171–172(2012) 405-408. [5] K. Ahn, M. Kim, K. Kim, I. Oh, H. Ju, J. Kim, Polymer. 56(2015) 178-188. [6] P. Shrivastava, S. Dalai, P. Sudera, S. Vijayalakshmi, P. Sharma, Microelectronic Engineering. 126(2014) 103-106. [7] Y. Li, L. Qiao, D. Yan, L. Wang, Y. Zeng, H.Yang, Journal of Alloys and Compounds. 586(2014) 399-403. [8] S.B. Wang, X.Q. Wang, H.L. Zhang, W.B. Zhang, Journal of Alloys and Compounds. 685(2016) 22-27. [9] J. L. Liu, W. Liu, Q. Sun, S. G. Wang, K. Sun, J. Schwank, R. M. Wang, Chem. Commun. 50(2014) 1804-1807. [10]X. Yan, Z. Lei, Journal of Colloid and Interface Science. 362(2011) 253-260. [11]W. Liu, K. Sun, R. M. Wang, Nanoscale. 5(2013) 5067-5072. [12]H. Cong, J. Wang, B. Yu, J. Tang, W. Cui, Journal of Colloid and Interface Science. 411(2013) 41-46. [13]G. Wang, H. Zou, L. Gong, Z. Shi, X. Xu, Y. Sheng, Powder Technology. 258(2014) 174-179. [14]D. Yang, S, Chen, P. Huang, X. Wang, W. Jiang , O. Pandoli, D. Cui, Green Chem. 12(2010) 2038-2042. [15]B. Bai, P. Wang, L. Wu, L.Yang, Z. Chen, Materials Chemistry and Physics. 114(2009) 26–29. [16]R. F. Martins, M. F. Ramos, L. Herfindal, J. A. Sousa, K. Skerven, V. M. Vasconcelos, Marine Drugs. 6(2008) 1-11. [17] A. M.L. van de Meene, M. F. Hohmann-Marriott, W. F.J. Vermaas, R. W. Roberson, Archives of Microbiology. 184 (2006) 259-270. [18]K. J. Riley, T. Reinot, R. Jankowiak, P. Fromme, V. Zazubovich, J. Phys. Chem. B 111(2007) 286–292. [19]T. Kaneko, S. Tabata, Jpn Soc Plant Physiol. 38 (1997) 1171-1176. [20]J. Panoff, B. Priem, H. Morvan, F. Joset, Archives of Microbiology. 150 (1988) 558-563. [21]G. Li, D. Chen, W. Zhao, X. Zhang, Journal of Environmental Chemical Engineering. 3(2015) 515-522. [22]T. Ito, R. Sadanaga, Acta Cryst. 4(1951) 385-390. [23]F. Yavuz, N. Karakaya, D. K. Yıldırım, M. Ç. Karakaya, M. Kumral, Computers & Geosciences. 63(2014) 70-87. [24]T. Nakamura, T. Kubo, Ferroelectrics. 137 (1992) 13-31. [25]J. U. Akoh, P. O. Ogunleye, Journal of Geochemical Exploration. 146(2014) 89-104. [26]M. Xia, C. Hu, H. Zhang, Process Biochemistry. 41(2006) 221–225. [27]B. Sarrasin, Journal of Cleaner Production. 14 (2006) 388–396. [28]Y. Hu, P. Xiong, X. Yang, IEIT Journal of Adaptive & Dynamic Computing. 1 (2011) 6-11. [29]L. D. Tijing, M. T. G. Ruelo, A. Amarjargal, H. R. Pant, C. Park, D. W. Kim, C. S. Kim, Chemical Engineering Journal. 197 (2012) 41-48. [30]B. Du, L. Zheng, Q. Wei, The Journal of The Textile Institute. 106 (2015) 787-791. [31]Z. Wu, H. Wang, K. Zheng, M. Xue, P. C, X. Tian, J. Phys. Chem. C 116 (2012) 12814–12818. [32]C. Wang, P. Wang, Y. Li, Y. Zhao, Construction and Building Materials. 80 (2015) 195-199 [33]J. Liang, J. Meng, D. Zhu, Y. Ding, Z. Liu, Journal of the Chinese Ceramic Society, 36(2008) 257-260. [34]J. Liang, L. Wang, G. Xu, J. Meng, Y. Ding, Journal of Rare Earths, 24(2006) 281-283. [35]Y. Pan，J. Liang, X. Ou, J. Meng, G. Liang, Journal of the Chinese Ceramic Society, 34(2006) 580-584.
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The conglobate synechocystis sp. as a novel biological template was applied. Tourmaline was firstly added into the precursor implanted by synechocystis sp. The structure of regular spherical hollow microspheres was confirmed by TEM directly.
S0925-8388(16)32893-6
DOI:
10.1016/j.jallcom.2016.09.141
Reference:
JALCOM 38975
To appear in:
Journal of Alloys and Compounds
Received Date: 14 July 2016 Revised Date:
2 September 2016
Accepted Date: 13 September 2016
Please cite this article as: F. Wang, H. Zhang, J. Liang, D. Feng, Q. Tang, K. Yu, Z. Shang, Effect of tourmaline mineral materials on the structure of silicon dioxide hollow microspheres prepared via a novel template, Journal of Alloys and Compounds (2016), doi: 10.1016/j.jallcom.2016.09.141. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Effect of tourmaline mineral materials on the structure of silicon dioxide hollow microspheres prepared via a novel template Fei Wang1,2, , Hui Zhang1,2, Jinsheng Liang1,2, Dan Feng1,2, ﹡
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Qingguo Tang1,2, Kaihua Yu1,2, Zengyao Shang1,2 1
Institute of Power Source & Ecomaterials Science, Hebei University of Technology, 300130 Tianjin, China Key Laboratory of Special Functional Materials for Ecological Environment and Information, Hebei University of Technology, Ministry of Education, Tianjin 300130, China ﹡correspondence author: [email protected]
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Keywords: tourmaline; mineral materials; silicon dioxide; hollow microspheres; biological template
Introduction
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Abstract. In this article, the silica hollow microspheres were prepared through the sol-gel method, using conglobate synechocystis sp. as a novel biological template. The pretreated synechocystis sp. was implanted into the silica precursor, and then solidified into shell on the surface of synechocystis sp. template by means of condensation polymerization reaction along with base catalysts. Meanwhile, the tourmaline mineral materials for performance optimization were added into the silica precursor implanted with synechocystis sp. The effect of tourmaline mineral materials on the structure of silicon dioxide hollow microspheres was studied systematically. Experimental results showed that regular spherical silica hollow microspheres as prepared have average particle size of about 2µm and uniform shell-thickness of about 80 nm. The sol-gel process of TEOS could be accelerated by adding tourmaline, leading to the agglomeration degree decrease of silica hollow microspheres. The above phenomenon could be ascribed to enhancement of water molecules ionization due to spontaneous polarization and far-infrared properties of tourmaline mineral materials, which accelerates the hydrolysis-condensation rate of TEOS. At the same time, the ion concentration in solution was reduced by spontaneous polarization, and the compressed degree on diffused electric double layer was also decreased. The silica hollow microspheres as prepared exhibited regular hollow spherical structure, thus acting as a promising candidate in the field of thermal insulation materials.
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Due to the characteristics of low cost, high hardness, heat insulation and fire resistance etc., hollow glass microspheres have been researched by many scientists in the fields of highly selective catalyst or catalyst carrier, electrocatalysis, lithium battery, light filler, low dielectric constant materials, controlled drug transport and slow release, disease diagnosis and so on[1-7]. In recent years, the preparation method of hollow microspheres has gradually become the focus of attention, and the template method has become one of the important preparation methods. The disadvantages of the common hard and soft template method were toxic byproducts formation, high cost, and severe pollution during the production process [8-12]. Biological template method is a new method to prepare the special structure material using the microorganism as raw material, which overcomes the disadvantages of common hard and soft template methods. At present, biological template methods have been widely used in the preparation of hollow microspheres, and the biological templates often use natural organisms, including algae, pollen, bacteria, and viruses[13-15]. Cyanobacteria synechocystis has good roundness and strong dispersion, which is easy to obtain in the short term due to the simple training process and condition [16-20]. Tourmaline mineral materials as a kind of borate mineral have many unique properties [21-25]. Due to the characteristics of negative ions generation, far infrared emitting, permanent electrode effect and electrostatic fields 1
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formation, tourmaline mineral materials have been applied in many fields, including environmental protection [27], human health[28], chemical engineering [29], health care textile[30], electromagnetic shielding[31], and hardening agent materials [32]. Among them, the far-infrared emission and the spontaneous permanent electrode of tourmaline can play an important role in water activation, which could be applied to improve the structure of hollow microspheres in theory. However, to the authors’ knowledge, there is no report about the studies of the effects of tourmaline mineral materials on the structure of silicon dioxide hollow microspheres prepared by the biological template. In this study, the silica hollow microspheres were prepared by the sol-gel method, using conglobate synechocystis sp. as a novel biological template, and the effect of tourmaline mineral materials on the silicon dioxide hollow microspheres structure was also investigated.
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Synechocystis sp. was supplied by Freshwater Algae Culture Collection at the Institute of Hydrobiology. The tourmaline which is one of natural mineral materials was purchased from Hebei province of China. The compounding ingredients were supplied by Fengchuan and Bodi Chemical Group Co., Ltd. The preparation process of silicon dioxide hollow microspheres is as follows. The mother liquid of synechocystis medium was prepared, according to the BG11 (Blue-Green Medium) liquid medium formula. The mother liquid, deionized water and glassware used in the inoculation process of algal cells were treated by high temperature and pressure sterilization. The algae culture solution was formed by constant volume mixing mother liquid and deionized water after cooling, accordance to the BG11 medium ratio. Then the synechocystis was moved into the culture bottle, which was full of the algae culture solution. Finally, the culture bottle was put into the artificial climate incubator for 15 days at 30 oC with 2000lx of light intensity. Moreover, the light irradiation time was 12h, and the pH value was 8. After that, the cultivated synechocystis sp. liquid was prepared. On the above basis, the dehydrated synechocystis was obtained by many dehydration and centrifugation process, using 4 vol.% of formaldehyde solution and different concentration levels of ethanol solution. The tourmaline was broken into small powders with diameter of about 1~2 mm, and the powders were ball milled for 2.5 h at 1100 r/min. Then the ball milled powders were dried at 60 oC , and heated at 800 oC for
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3h [33-35]. The 3 ml TEOS and 10 ml anhydrous ethanol were mixed into solution A, and the solution B was formed by mixing 3 ml of concentrated ammonia water (27%), 10 ml of water and 9 ml anhydrous ethanol. The appropriate amount of treated synechocystis was added into the solution B, and the mixture was treated by ultrasonic wave for 2min, in order to make water and concentrated ammonia water adsorb quickly and evenly on the surface of the cell. Then the solution A was slowly added into the solution B in the stirring process, in order to make the formed silicon dioxide colloidal particles coated evenly on the surface of the algal cells. After that, 0.2 g of heat treated tourmaline was added into the mixed liquid. Then the mixture was stirred at room temperature for 36 h, and was aged at room temperature for 24 h. Then the solid phase was collected by centrifugation, washing and drying. Finally, the silicon dioxide hollow microspheres were prepared by calcination at 550 oC for 8 h. Scanning electron microscopy (S-4800, SEM, Hitachi Limited, Tokyo, Japan) was used to observe sample morphological features at an acceleration voltage of 3kVA, and the X-ray diffraction (XRD) analysis was performed on a Philips-DMAX-2500 with Cu Kα radiation. The Fourier transform infrared spectrum (FTIR) was performed on a BRUKER-80V made in Germany using KBr discs to monitor changes of functional groups during chemical modification. The microstructure of silicon dioxide hollow microspheres was analyzed by JEM-2010 TEM.
Results and discussion 2
ACCEPTED MANUSCRIPT The silica microspheres were prepared by using synechocystis of dehydration pretreatment as template with concentrated ammonia water as a catalytic agent. The effect of tourmaline addition on the prepared microspheres microstructure was shown in Fig.1.
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Fig.1 SEM images showing the microstructure of silicon dioxide hollow microspheres using base as catalyst (a) adding no tourmaline, (b) adding tourmaline
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From Fig.1(a), it can be seen that the microspheres maintained the regular spherical morphology of synechocystis bio templates in a large extent. After the preparation process of stirring, aging and calcination, a lot of spherical particles appeared on the surface and the surrounding of microspheres. The microspheres surface was uneven, and the average diameter was about 2µm. Among them, the point of the arrow was the damaged hole of a microsphere, which can be inferred that TEOS formed a shell reacted on the cell surface. Moreover, the dispersion and size uniformity of microspheres was low. On the other hand, we can see from Fig.1(b) that regular spherical silica hollow microspheres as prepared have average particle size of about 2µm. With alkali as the catalyst, the formation of sphere wall was arranged by the particles which closely connected by van der Waals’ force and hydrogen bond or chemical bond, and microspheres surface was rugged. Furthermore, it can be seen from the observation of samples collected by centrifugation after aging, in the same time, the silica microspheres yield of adding tourmaline sample was 50% higher than the case without adding tourmaline. From Fig.1(b), it also can be seen that the dispersion of samples were improved after adding tourmaline in the process. Moreover, we can see from the energy spectra (Fig.2) that the components of the samples are mainly composed by Si and O elements, which is consistent of silicon dioxide hollow microspheres.
Fig.2 Energy spectra of the sample as-prepared The TEM image of silicon dioxide hollow microspheres after adding tourmaline was shown in Fig.3.
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Fig.3. TEM image taken from silicon dioxide hollow microspheres after adding tourmaline
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It can be seen from the Fig.3 that the synechocystis cells were in normal growth stage, and the silica microspheres maintained the spherical morphology of the synechocystis. Bright-field TEM contrast has a nature of two dimensional projection of mass thickness accumulating along beam direction. A significant difference with light and dark in the microspheres can be found, indicating that the microspheres have a hollow structure. The arrow 1 points to the outer wall of the microsphere, and the arrow 2 points to the inner wall of the microsphere. It can be seen that the algae have been removed by calcination and the silica hollow microspheres have been prepared successfully. On the basis, the wall thickness of hollow microspheres is about 80nm, which is obtained by using digital micrograph software. Fig. 4 displays the XRD patterns from the silicon dioxide hollow microspheres using base as catalyst (a) adding no tourmaline, (b) adding tourmaline, respectively.
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Fig.4 XRD pattern of silicon dioxide hollow microspheres using base as catalyst (a) adding no tourmaline, (b) adding tourmaline It can be seen from Fig.4(a) that samples were amorphous state, which showed that the crystal of the sample 4
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could not be changed by calcination. From Fig.4(b), we can see that the mainly diffraction peaks were tourmaline (T), SiO2 (s), spinel (m) and iron oxide (f); the latter two were caused by the heating process at 800 oC. Moreover, the crystal plane indexes {hkl} of tourmaline characteristic peaks were (211), (220) and (051). However, the characteristic peak of SiO2 still existed, showing that adding tourmaline would not affect the hydrolysis condensation process of TEOS. In addition, the XRD diffraction peak of prepared silicon dioxide microspheres adding tourmaline was wider obviously, indicating the larger extent of amorphization. To further confirm the silicon dioxide microspheres structure, chemical characteristics of the different samples were monitored by FT-IR with the results shown in Fig. 5.
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Fig.5 FT-IR spectra of silicon dioxide hollow microspheres using base as catalyst (a) adding no tourmaline, (b) adding tourmaline
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In Fig.5, some absorption peaks between 400 and 600 cm-1 can be ascribed as Si-O stretching vibration, Si-O-Si symmetric stretching vibration, B-O deformation vibration and M-O stretching vibration of metal ions; some absorption peaks between 1000 and 1200 cm-1, between 1200 and 1450 cm-1, between 3250 and 3750 cm-1, and 1626 cm-1 can be labeled as Si-O-Si anti symmetric stretching vibration, B-O symmetric stretching vibration, O-H bond stretching vibration of structure water or adsorbed water and O-H bond bending vibration. Compared with silicon dioxide microspheres adding no tourmaline, Si-O-Si vibration peaks of silicon dioxide microspheres with tourmaline shift to lower wave number, which indicates the smaller group stability of silicon dioxide microspheres after adding tourmaline in the preparation process. The effect of tourmaline on the growth of silicon dioxide microspheres grown on the synechocystis with the alkaline catalyst condition is analyzed as follows. The hydrolysis reaction of positive ethyl silicate is the OHnucleophilic attack Si atom, and OH- plays a catalytic role. The H+ and OH- concentration in the water is increased by the spontaneous polarization properties of tourmaline, accelerating the hydrolysis condensation reaction and the aggregation of small colloidal particles on the surface of synechocystis. At the same time, the clusters of water molecules are reduced due to the far infrared emission of tourmaline, and the hydrolysis condensation reaction is accelerated due to the decrease of the resistance in the colloid diffusion process. Fig.6 shows the silicon dioxide hollow microspheres preparation process at alkali catalysts after adding heated tourmaline.
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Fig.6 Preparation diagram of silicon dioxide hollow microspheres at alkali catalysts after adding heated tourmaline
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From Fig.6, we can see that the OH- in the catalyst is adsorbed rapidly on the surface of synechocystis implanted into the solution B. After the addition of TEOS, a small amount of TEOS is combined with OH- on the surface of synechocystis, and then submicron particles generated by hydrolysis reaction are concluded to nucleus. Moreover, more submicron particles generated by the extracellular solution also form the nucleus with the increase of the addition amount of TEOS. The sub micro particles core is formed on the surface of the synechocystis by diffusion and collision, and the particles are grown up by the surface reaction and diffusion control mechanisms.
Conclusions
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In this work, the silica hollow microspheres were obtained using conglobate synechocystis sp. as a novel biological template, and the effect of tourmaline mineral materials on the structure of silicon dioxide hollow microspheres was studied systematically. The results showed that regular spherical silica hollow microspheres as prepared have average particle size of about 2µm and uniform shell-thickness of about 80 nm. A significant contrast difference of light and dark in the microspheres can be found in the TEM image, confirming that the microspheres have a hollow structure. The sol-gel process of TEOS could be accelerated by adding tourmaline, thus the agglomeration degree of silica hollow microspheres decreased. The reason for the above phenomenon was that the ionization of water molecules was enhanced by spontaneous polarization and far-infrared properties of tourmaline, and the hydrolysis-condensation rate of TEOS was accelerated. Meanwhile, the ion concentration in solution was reduced due to spontaneous polarization, and the compressed degree on diffused electric double layer was also reduced.
Acknowledgements
This research was financially supported by the National Natural Science Foundation of China (Grant no. 51404085), Key Technology R&D Program of Tianjin city (Grant no. 15ZCZDSF00030), China Postdoctoral Science Foundation (Grant no. 2015M571255), and Natural Science Foundation of Hebei province (Grant no. E2013202142). References [1] L. Renuka, K.S. Anantharaju, S.C. Sharma, H.P. Nagaswarupa, S.C. Prashantha, H. Nagabhushana, Y.S. Vidya, Journal of Alloys and Compounds. 672 (2016) 609-622. 6
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The conglobate synechocystis sp. as a novel biological template was applied. Tourmaline was firstly added into the precursor implanted by synechocystis sp. The structure of regular spherical hollow microspheres was confirmed by TEM directly.