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Expeditious synthesis of SnO2 nanoparticles through controlled hydrolysis and condensation of Tin alkoxide in reverse microemulsion
Ceramics International (xxxx) xxxx–xxxx
Contents lists available at ScienceDirect
Ceramics International journal homepage: www.elsevier.com/locate/ceramint
Short communication
Expeditious synthesis of SnO2 nanoparticles through controlled hydrolysis and condensation of Tin alkoxide in reverse microemulsion ⁎
Jiasheng Wanga,b, , Wenpei Wua,b, Wan-Hui Wanga,b, Ming Baoa,b, a b
⁎
State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116023, China School of Petroleum and Chemical Engineering, Dalian University of Technology, Panjin 124221, China
A R T I C L E I N F O
A BS T RAC T
Keywords: Tin alkoxide Controlled hydrolysis and condensation SnO2 nanoparticles Reverse microemulsion
SnO2 is a very important material in many areas such as catalysis, gas sensors, and lithium ion batteries. In this study, we successfully prepared SnO2 nanoparticles from tin (IV) isopropoxide in reverse microemulsion, which is still a big challenge up to now due to the uncontrollable hydrolysis and condensation rate. The hydrolysis and condensation process was slowed down by diffusion limitation, i.e., increasing the viscosity of the reaction media by introducing PVA-224 to the reverse microemulsion. The strategy developed here is of general directive significance for preparing other metal oxide nanoparticles in reverse microemulsion from corresponding metal alkoxide precursors who have fast hydrolysis and condensation rate.
1. Introduction SnO2 is a very important material in many areas such as photocatalysis [1], gas sensors [2], supercapacitors [3], and lithium ion batteries [4]. The property and application of SnO2 strongly depend on its size and morphology. Therefore, it is very important to synthesize SnO2 nanoparticles with desired size and morphology. Reverse microemulsion is a powerful tool to synthesize certain sized nanoparticles [5,6]. However, though it has been very successful to synthesize silica-based nanocomposites [7], the synthesis of SnO2 is not yet very satisfying. Traditionally SnCl4 was used as the precursor [8,9]. But its reaction with NH3·H2O is so fast that the reverse microemulsion cannot efficiently restrict the product morphology. The success of SiO2 from TEOS [7] tells us that the sol-gel method involving the hydrolysis and condensation of metal alkoxide is a promising method to get nanoparticles with good morphology. However, the hydrolysis and condensation rate of tin alkoxide is also too fast to control [10]. Gyger et al. have managed to slow down the reaction rate by reducing the concentration of tin (IV) tertbutoxide (TTBT) to 0.01 M [11], which makes it impossible for mass production. Thus there is still an urgent need to develop other practical methods to efficiently control the hydrolysis and condensation process. Increasing the viscosity to limit the reaction rate is a promising method [12]. To increase the viscosity, one plausible way is introducing viscosifier in the system. According to the unique structure of reverse microemulsion, which consists aqueous phase and oil phase, the viscosifier should be hydrosoluble and meanwhile oleophobic to only
⁎
increase the viscosity of the aqueous phase where the reactions occur. Hydrosoluble polymers thus come into sight. Among the many hydrosoluble polymers, polyvinyl alcohol (PVA), whose viscosity can be adjusted in a wide range, is an appropriate option. In this study, we successfully prepared SnO2 nanoparticles from tin (IV) isopropoxide (TIPP) in reverse microemulsion. The hydrolysis and condensation process was slowed down by introducing PVA-224 into the microemulsion system and making it a diffusion-controlled process. The strategy can be extended to synthesize other metal oxide nanoparticles from the hydrolysis and condensation of corresponding metal alkoxide via reverse microemulsion method. 2. Experimental 2.1. Materials Tin (IV) isopropoxide (TIPP, 10% w/v in isopropanol) was purchased from J & K Scientific Ltd. Cetyltrimethylammonium Bromide (CTAB), cyclohexane, n-butanol, and isopropanol were of analytical grade and purchased from Sinopharm Chemical Reagent Co., Ltd. (SCRC). Polyvinyl alcohols (PVA0588, PVA1788, PVA-124, and PVA224) were purchased from Shanghai Macklin Biochemical Co., Ltd. All chemicals were directly used without further purification. 2.2. Synthesis of SnO2 nanoparticles In a typical synthesis procedure, 2.916 g of CTAB and 4 mL of n-
Corresponding authors at: State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116023, China E-mail addresses: [email protected] (J. Wang), [email protected] (M. Bao).
http://dx.doi.org/10.1016/j.ceramint.2017.01.002 Received 14 November 2016; Received in revised form 28 December 2016; Accepted 2 January 2017 0272-8842/ © 2017 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Please cite this article as: Wang, J., Ceramics International (2017), http://dx.doi.org/10.1016/j.ceramint.2017.01.002
Ceramics International (xxxx) xxxx–xxxx
J. Wang et al.
butanol were added to 14 mL of cyclohexane in a 50-mL two-necked round-bottomed flask. The mixture was heated to 55 °C under stirring to form a transparent solution. 1 mL of 4 wt% PVA aqueous solution was added in 4 batches at an interval of 5 min to form a reverse microemulsion system. Then the system was cooled to 30 °C. 0.6 mL of TIPP (10% w/v in isopropanol) was added in 3 batches at an interval of 8 min. The reaction was allowed to proceed for 2 h, after which 15 mL of IPA was added to demulsificate the microemulsion. After ultrasonication for 5 min, the mixture was centrifuged at 6000 rpm for 10 min. The precipitate was washed with cyclohexane twice, freeze dried at −50 °C for 10 h and then calcined at 500 °C for 2 h under air stream to give the product. If PVA is absent in the synthesis process, SnO2 nanoclusters below 2 nm would be obtained. 2.3. Characterization Fig. 2. XRD pattern for SnO2 nanoparticles.
TEM was performed at room temperature on a JEOL JEM-2000 EX transmission electron microscope using an accelerating voltage of 120 kV. High-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) were conducted on a FEI Tecnai G2 F20 microscope working at 200 kV. The XRD patterns were recorded on a SHIMADZU X-ray diffractometer (XRD-7000S) with CuKα (0.1542 nm) radiation, scanning from 10° to 90° (2θ) at a rate of 6°/min.
HRTEM image and SAED pattern are shown in Fig. 1c and d, respectively. From the HRTEM we can see clear fringes of the lattice planes (marked by red short parallel lines). The interplanar distance of 3.35 Å can be attributed to cassiterite SnO2 (110). The SAED pattern exhibits a number of bright concentric rings, which correspond to the (110), (101), (211), and (112) planes of cassiterite SnO2. Among those planes, (110) is the brightest one, which is in accordance with the plane shown in Fig. 1c. The XRD pattern of SnO2 nanoparticles was shown in Fig. 2. As expected, the positions of all diffraction peaks in the XRD pattern match well with the standard powder diffraction data of SnO2 (JCPDS No. 99-0024). The morphology and size of the SnO2 prepared without PVA were characterized using TEM and displayed in Fig. 3. As shown in Fig. 3a and b, the SnO2 obtained were only 1.4 ± 0.6 nm, so-called nanoclus-
3. Results and discussion 3.1. Characterization of SnO2 nanoparticles Fig. 1a and b show the TEM image and size distribution histogram of the obtained SnO2 nanoparticles, respectively. We can see that the particles are spherical with an average diameter of 9.7 ± 1.2 nm. The
Fig. 1. (a) TEM image, (b) particle size distribution histogram, (c) HRTEM image and (d) SAED pattern of SnO2 nanoparticles.
2
Ceramics International (xxxx) xxxx–xxxx
J. Wang et al.
Fig. 3. (a) TEM image and (b) particle size distribution histogram of SnO2 nanoclusters.
ters ( < 2 nm) [13], which is much smaller than the micelle size of the reverse microemulsion.
3.2. Formation process and control mechanism of SnO2 nanoparticles How to judge that the hydrolysis and condensation of metal alkoxide is successfully controlled? The answer is that the size of the particles should be similar to that of the water pool of the reverse microemulsion. Only in this way can we say that the formation of the particles is controlled by the reverse microemulsion. If the hydrolysis and condensation rate are too fast, huge amount of crystal nucleus would emerge instantaneously, less SnO2 precursor was available for each particle to grow, and then the particles would be very small, which could be well supported by Fig. 3. Sn(OC3H7)4+4H2O→Sn(OH)4+4C3H7OH
Sn(OH)4→SnO2+2 H2O
Scheme 1. Illustration of the formation mechanism of SnO2 nanoclusters and nanoparticles.
(a)
Table 1 The parameters of PVA series.
(b)
The sol-gel process for preparing SnO2 is based on the hydrolysis and condensation of tin alkoxide compounds (Eqs. (a) and (b)). Hydrolysis replaces the alkoxide groups with hydroxyl groups [10]. Subsequent condensation reactions involving the hydroxyl groups produce Sn-O-Sn bonds and other by-products (water or isopropanol). In reverse microemulsions, such hydrolysis and condensation occurred in the water pool of the w/o micelles. To control the hydrolysis and condensation of TIPP, the diffusion inside the water-filled micelles was limited upon increasing the viscosity of the aqueous phase by the addition of PVA, a hydrosoluble and oleophobic polymer. If PVA was absence, the hydrolysis and condensation of TIPP would be too fast, leading to small nanoclusters only. As shown in Scheme 1. PVA acted just like a cobweb which can trap the tin alkoxide compounds (completely or partially hydrolyzed), thus slowed down the reaction rate efficiently. A series of PVA were tried, as shown in Table 1. Among them the PVA-224 with medium viscosity was optimal. If the viscosity is low, the reaction rate cannot be efficiently slowed. However, if the viscosity is too high, it is difficult to form stable microemulsion system. The freeze-drying step is also very important here. If the gel is dried by simple evaporation, there will be large capillary forces at the curved liquid–vapor interfaces, which often cause the material to shrink and even crack. Thus freeze-drying which can suppress the liquid–vapor interface or reduce the capillary forces was adopted.
PVA series
M.W.
Viscosity (4%) mPa s
Alcoholysis degree
Polymerization degree
PVA0588 PVA1788 PVA-224
27,000 74,800 105,600– 110,000 105,600– 110,000
5.0–6.0 21.0–26.0 40.0–48.0
87–89% 87–89% 87–89%
550 1700 2400
54.0–66.0
98–99%
2400
PVA-124
4. Conclusions In summary, SnO2 nanoparticles were synthesized by controlled hydrolysis of tin alkoxide. The hydrolysis and condensation process was slowed down by increasing the viscosity of the reaction media by introducing PVA-224 into the reverse microemulsion system. The strategy developed here is of general directive significance for preparing metal oxide nanoparticles (such as TiO2, ZrO2, Al2O3, etc.) from the hydrolysis and condensation of corresponding metal alkoxide via reverse microemulsion method. Acknowledgements The authors gratefully acknowledge the financial support of the Fundamental Research Funds for the Central Universities (Grant No. 3
Ceramics International (xxxx) xxxx–xxxx
J. Wang et al.
[6] J. Wang, X. Li, S. Zhang, R. Lu, Facile synthesis of ultrasmall monodisperse "raisinbun"-type MoO3/SiO2 nanocomposites with enhanced catalytic properties, Nanoscale 5 (2013) 4823–4828. [7] J. Wang, Z.H. Shah, S. Zhang, R. Lu, Silica-based nanocomposites via reverse microemulsions: classifications, preparations, and applications, Nanoscale 6 (2014) 4418–4437. [8] K.C. Song, J.H. Kim, Preparation of nanosize tin oxide particles from water-in-oil microemulsions, J. Colloid Interf. Sci. 212 (1999) 193–196. [9] N. Zamand, A. Nakhaei Pour, M.R. Housaindokht, M. Izadyar, Size-controlled synthesis of SnO2 nanoparticles using reverse microemulsion method, Solid State Sci. 33 (2014) 6–11. [10] M.J. Hampden-Smith, T.A. Wark, C.J. Brinker, The solid state and solution structures of tin(IV) alkoxide compounds and their use as precursors to form tin oxide ceramics via sol-gel-type hydrolysis and condensation, Coord. Chem. Rev. 112 (1992) 81–116. [11] F. Gyger, M. Hübner, C. Feldmann, N. Barsan, U. Weimar, Nanoscale SnO2 hollow spheres and their application as a gas-sensing material, Chem. Mater. 22 (2010) 4821–4827. [12] C. Zurmühl, R. Popescu, D. Gerthsen, C. Feldmann, Microemulsion-based synthesis of nanoscale TiO2 hollow spheres, Solid State Sci. 13 (2011) 1505–1509. [13] Y. Lu, W. Chen, Sub-nanometre sized metal clusters: from synthetic challenges to the unique property discoveries, Chem. Soc. Rev. 41 (2012) 3594–3623.
DUT15QY57). This work is also supported by the National Natural Science Foundation of China (No. 21506026) and Doctoral Scientific Research Foundation of Liaoning Province (No. 201501171). References [1] N. Talebian, F. Jafarinezhad, Morphology-controlled synthesis of SnO2 nanostructures using hydrothermal method and their photocatalytic applications, Ceram. Int. 39 (2013) 8311–8317. [2] Q. Wang, N. Yao, D. An, Y. Li, Y. Zou, X. Lian, X. Tong, Enhanced gas sensing properties of hierarchical SnO2 nanoflower assembled from nanorods via a one-pot template-free hydrothermal method, Ceram. Int. 42 (2016) 15889–15896. [3] S.P. Lim, N.M. Huang, H.N. Lim, Solvothermal synthesis of SnO2/graphene nanocomposites for supercapacitor application, Ceram. Int. 39 (2013) 6647–6655. [4] L. Yin, S. Chai, F. Wang, J. Huang, J. Li, C. Liu, X. Kong, Ultrafine SnO2 nanoparticles as a high performance anode material for lithium ion battery, Ceram. Int. 42 (2016) 9433–9437. [5] J. Wang, X. Li, L. Luo, S. Zhang, R. Lu, Core–shell BaMoO4@SiO2 nanospheres: preparation, characterization, and optical properties, Ceram. Int. 39 (2013) 9293–9298.
4
Contents lists available at ScienceDirect
Ceramics International journal homepage: www.elsevier.com/locate/ceramint
Short communication
Expeditious synthesis of SnO2 nanoparticles through controlled hydrolysis and condensation of Tin alkoxide in reverse microemulsion ⁎
Jiasheng Wanga,b, , Wenpei Wua,b, Wan-Hui Wanga,b, Ming Baoa,b, a b
⁎
State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116023, China School of Petroleum and Chemical Engineering, Dalian University of Technology, Panjin 124221, China
A R T I C L E I N F O
A BS T RAC T
Keywords: Tin alkoxide Controlled hydrolysis and condensation SnO2 nanoparticles Reverse microemulsion
SnO2 is a very important material in many areas such as catalysis, gas sensors, and lithium ion batteries. In this study, we successfully prepared SnO2 nanoparticles from tin (IV) isopropoxide in reverse microemulsion, which is still a big challenge up to now due to the uncontrollable hydrolysis and condensation rate. The hydrolysis and condensation process was slowed down by diffusion limitation, i.e., increasing the viscosity of the reaction media by introducing PVA-224 to the reverse microemulsion. The strategy developed here is of general directive significance for preparing other metal oxide nanoparticles in reverse microemulsion from corresponding metal alkoxide precursors who have fast hydrolysis and condensation rate.
1. Introduction SnO2 is a very important material in many areas such as photocatalysis [1], gas sensors [2], supercapacitors [3], and lithium ion batteries [4]. The property and application of SnO2 strongly depend on its size and morphology. Therefore, it is very important to synthesize SnO2 nanoparticles with desired size and morphology. Reverse microemulsion is a powerful tool to synthesize certain sized nanoparticles [5,6]. However, though it has been very successful to synthesize silica-based nanocomposites [7], the synthesis of SnO2 is not yet very satisfying. Traditionally SnCl4 was used as the precursor [8,9]. But its reaction with NH3·H2O is so fast that the reverse microemulsion cannot efficiently restrict the product morphology. The success of SiO2 from TEOS [7] tells us that the sol-gel method involving the hydrolysis and condensation of metal alkoxide is a promising method to get nanoparticles with good morphology. However, the hydrolysis and condensation rate of tin alkoxide is also too fast to control [10]. Gyger et al. have managed to slow down the reaction rate by reducing the concentration of tin (IV) tertbutoxide (TTBT) to 0.01 M [11], which makes it impossible for mass production. Thus there is still an urgent need to develop other practical methods to efficiently control the hydrolysis and condensation process. Increasing the viscosity to limit the reaction rate is a promising method [12]. To increase the viscosity, one plausible way is introducing viscosifier in the system. According to the unique structure of reverse microemulsion, which consists aqueous phase and oil phase, the viscosifier should be hydrosoluble and meanwhile oleophobic to only
⁎
increase the viscosity of the aqueous phase where the reactions occur. Hydrosoluble polymers thus come into sight. Among the many hydrosoluble polymers, polyvinyl alcohol (PVA), whose viscosity can be adjusted in a wide range, is an appropriate option. In this study, we successfully prepared SnO2 nanoparticles from tin (IV) isopropoxide (TIPP) in reverse microemulsion. The hydrolysis and condensation process was slowed down by introducing PVA-224 into the microemulsion system and making it a diffusion-controlled process. The strategy can be extended to synthesize other metal oxide nanoparticles from the hydrolysis and condensation of corresponding metal alkoxide via reverse microemulsion method. 2. Experimental 2.1. Materials Tin (IV) isopropoxide (TIPP, 10% w/v in isopropanol) was purchased from J & K Scientific Ltd. Cetyltrimethylammonium Bromide (CTAB), cyclohexane, n-butanol, and isopropanol were of analytical grade and purchased from Sinopharm Chemical Reagent Co., Ltd. (SCRC). Polyvinyl alcohols (PVA0588, PVA1788, PVA-124, and PVA224) were purchased from Shanghai Macklin Biochemical Co., Ltd. All chemicals were directly used without further purification. 2.2. Synthesis of SnO2 nanoparticles In a typical synthesis procedure, 2.916 g of CTAB and 4 mL of n-
Corresponding authors at: State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116023, China E-mail addresses: [email protected] (J. Wang), [email protected] (M. Bao).
http://dx.doi.org/10.1016/j.ceramint.2017.01.002 Received 14 November 2016; Received in revised form 28 December 2016; Accepted 2 January 2017 0272-8842/ © 2017 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Please cite this article as: Wang, J., Ceramics International (2017), http://dx.doi.org/10.1016/j.ceramint.2017.01.002
Ceramics International (xxxx) xxxx–xxxx
J. Wang et al.
butanol were added to 14 mL of cyclohexane in a 50-mL two-necked round-bottomed flask. The mixture was heated to 55 °C under stirring to form a transparent solution. 1 mL of 4 wt% PVA aqueous solution was added in 4 batches at an interval of 5 min to form a reverse microemulsion system. Then the system was cooled to 30 °C. 0.6 mL of TIPP (10% w/v in isopropanol) was added in 3 batches at an interval of 8 min. The reaction was allowed to proceed for 2 h, after which 15 mL of IPA was added to demulsificate the microemulsion. After ultrasonication for 5 min, the mixture was centrifuged at 6000 rpm for 10 min. The precipitate was washed with cyclohexane twice, freeze dried at −50 °C for 10 h and then calcined at 500 °C for 2 h under air stream to give the product. If PVA is absent in the synthesis process, SnO2 nanoclusters below 2 nm would be obtained. 2.3. Characterization Fig. 2. XRD pattern for SnO2 nanoparticles.
TEM was performed at room temperature on a JEOL JEM-2000 EX transmission electron microscope using an accelerating voltage of 120 kV. High-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) were conducted on a FEI Tecnai G2 F20 microscope working at 200 kV. The XRD patterns were recorded on a SHIMADZU X-ray diffractometer (XRD-7000S) with CuKα (0.1542 nm) radiation, scanning from 10° to 90° (2θ) at a rate of 6°/min.
HRTEM image and SAED pattern are shown in Fig. 1c and d, respectively. From the HRTEM we can see clear fringes of the lattice planes (marked by red short parallel lines). The interplanar distance of 3.35 Å can be attributed to cassiterite SnO2 (110). The SAED pattern exhibits a number of bright concentric rings, which correspond to the (110), (101), (211), and (112) planes of cassiterite SnO2. Among those planes, (110) is the brightest one, which is in accordance with the plane shown in Fig. 1c. The XRD pattern of SnO2 nanoparticles was shown in Fig. 2. As expected, the positions of all diffraction peaks in the XRD pattern match well with the standard powder diffraction data of SnO2 (JCPDS No. 99-0024). The morphology and size of the SnO2 prepared without PVA were characterized using TEM and displayed in Fig. 3. As shown in Fig. 3a and b, the SnO2 obtained were only 1.4 ± 0.6 nm, so-called nanoclus-
3. Results and discussion 3.1. Characterization of SnO2 nanoparticles Fig. 1a and b show the TEM image and size distribution histogram of the obtained SnO2 nanoparticles, respectively. We can see that the particles are spherical with an average diameter of 9.7 ± 1.2 nm. The
Fig. 1. (a) TEM image, (b) particle size distribution histogram, (c) HRTEM image and (d) SAED pattern of SnO2 nanoparticles.
2
Ceramics International (xxxx) xxxx–xxxx
J. Wang et al.
Fig. 3. (a) TEM image and (b) particle size distribution histogram of SnO2 nanoclusters.
ters ( < 2 nm) [13], which is much smaller than the micelle size of the reverse microemulsion.
3.2. Formation process and control mechanism of SnO2 nanoparticles How to judge that the hydrolysis and condensation of metal alkoxide is successfully controlled? The answer is that the size of the particles should be similar to that of the water pool of the reverse microemulsion. Only in this way can we say that the formation of the particles is controlled by the reverse microemulsion. If the hydrolysis and condensation rate are too fast, huge amount of crystal nucleus would emerge instantaneously, less SnO2 precursor was available for each particle to grow, and then the particles would be very small, which could be well supported by Fig. 3. Sn(OC3H7)4+4H2O→Sn(OH)4+4C3H7OH
Sn(OH)4→SnO2+2 H2O
Scheme 1. Illustration of the formation mechanism of SnO2 nanoclusters and nanoparticles.
(a)
Table 1 The parameters of PVA series.
(b)
The sol-gel process for preparing SnO2 is based on the hydrolysis and condensation of tin alkoxide compounds (Eqs. (a) and (b)). Hydrolysis replaces the alkoxide groups with hydroxyl groups [10]. Subsequent condensation reactions involving the hydroxyl groups produce Sn-O-Sn bonds and other by-products (water or isopropanol). In reverse microemulsions, such hydrolysis and condensation occurred in the water pool of the w/o micelles. To control the hydrolysis and condensation of TIPP, the diffusion inside the water-filled micelles was limited upon increasing the viscosity of the aqueous phase by the addition of PVA, a hydrosoluble and oleophobic polymer. If PVA was absence, the hydrolysis and condensation of TIPP would be too fast, leading to small nanoclusters only. As shown in Scheme 1. PVA acted just like a cobweb which can trap the tin alkoxide compounds (completely or partially hydrolyzed), thus slowed down the reaction rate efficiently. A series of PVA were tried, as shown in Table 1. Among them the PVA-224 with medium viscosity was optimal. If the viscosity is low, the reaction rate cannot be efficiently slowed. However, if the viscosity is too high, it is difficult to form stable microemulsion system. The freeze-drying step is also very important here. If the gel is dried by simple evaporation, there will be large capillary forces at the curved liquid–vapor interfaces, which often cause the material to shrink and even crack. Thus freeze-drying which can suppress the liquid–vapor interface or reduce the capillary forces was adopted.
PVA series
M.W.
Viscosity (4%) mPa s
Alcoholysis degree
Polymerization degree
PVA0588 PVA1788 PVA-224
27,000 74,800 105,600– 110,000 105,600– 110,000
5.0–6.0 21.0–26.0 40.0–48.0
87–89% 87–89% 87–89%
550 1700 2400
54.0–66.0
98–99%
2400
PVA-124
4. Conclusions In summary, SnO2 nanoparticles were synthesized by controlled hydrolysis of tin alkoxide. The hydrolysis and condensation process was slowed down by increasing the viscosity of the reaction media by introducing PVA-224 into the reverse microemulsion system. The strategy developed here is of general directive significance for preparing metal oxide nanoparticles (such as TiO2, ZrO2, Al2O3, etc.) from the hydrolysis and condensation of corresponding metal alkoxide via reverse microemulsion method. Acknowledgements The authors gratefully acknowledge the financial support of the Fundamental Research Funds for the Central Universities (Grant No. 3
Ceramics International (xxxx) xxxx–xxxx
J. Wang et al.
[6] J. Wang, X. Li, S. Zhang, R. Lu, Facile synthesis of ultrasmall monodisperse "raisinbun"-type MoO3/SiO2 nanocomposites with enhanced catalytic properties, Nanoscale 5 (2013) 4823–4828. [7] J. Wang, Z.H. Shah, S. Zhang, R. Lu, Silica-based nanocomposites via reverse microemulsions: classifications, preparations, and applications, Nanoscale 6 (2014) 4418–4437. [8] K.C. Song, J.H. Kim, Preparation of nanosize tin oxide particles from water-in-oil microemulsions, J. Colloid Interf. Sci. 212 (1999) 193–196. [9] N. Zamand, A. Nakhaei Pour, M.R. Housaindokht, M. Izadyar, Size-controlled synthesis of SnO2 nanoparticles using reverse microemulsion method, Solid State Sci. 33 (2014) 6–11. [10] M.J. Hampden-Smith, T.A. Wark, C.J. Brinker, The solid state and solution structures of tin(IV) alkoxide compounds and their use as precursors to form tin oxide ceramics via sol-gel-type hydrolysis and condensation, Coord. Chem. Rev. 112 (1992) 81–116. [11] F. Gyger, M. Hübner, C. Feldmann, N. Barsan, U. Weimar, Nanoscale SnO2 hollow spheres and their application as a gas-sensing material, Chem. Mater. 22 (2010) 4821–4827. [12] C. Zurmühl, R. Popescu, D. Gerthsen, C. Feldmann, Microemulsion-based synthesis of nanoscale TiO2 hollow spheres, Solid State Sci. 13 (2011) 1505–1509. [13] Y. Lu, W. Chen, Sub-nanometre sized metal clusters: from synthetic challenges to the unique property discoveries, Chem. Soc. Rev. 41 (2012) 3594–3623.
DUT15QY57). This work is also supported by the National Natural Science Foundation of China (No. 21506026) and Doctoral Scientific Research Foundation of Liaoning Province (No. 201501171). References [1] N. Talebian, F. Jafarinezhad, Morphology-controlled synthesis of SnO2 nanostructures using hydrothermal method and their photocatalytic applications, Ceram. Int. 39 (2013) 8311–8317. [2] Q. Wang, N. Yao, D. An, Y. Li, Y. Zou, X. Lian, X. Tong, Enhanced gas sensing properties of hierarchical SnO2 nanoflower assembled from nanorods via a one-pot template-free hydrothermal method, Ceram. Int. 42 (2016) 15889–15896. [3] S.P. Lim, N.M. Huang, H.N. Lim, Solvothermal synthesis of SnO2/graphene nanocomposites for supercapacitor application, Ceram. Int. 39 (2013) 6647–6655. [4] L. Yin, S. Chai, F. Wang, J. Huang, J. Li, C. Liu, X. Kong, Ultrafine SnO2 nanoparticles as a high performance anode material for lithium ion battery, Ceram. Int. 42 (2016) 9433–9437. [5] J. Wang, X. Li, L. Luo, S. Zhang, R. Lu, Core–shell BaMoO4@SiO2 nanospheres: preparation, characterization, and optical properties, Ceram. Int. 39 (2013) 9293–9298.
4