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Hydrothermal synthesis of NiO nanobelts and the effect of sodium oxalate
Materials Letters 156 (2015) 25–27
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Hydrothermal synthesis of NiO nanobelts and the effect of sodium oxalate Shengkai Cao, Wen Zeng n, Tianmin Li, Jun Gong, Zhenjie Zhu College of Materials Science and Engineering, Chongqing University, Chongqing, China
art ic l e i nf o
a b s t r a c t
Article history: Received 16 March 2015 Accepted 29 April 2015 Available online 7 May 2015
Nanomaterials with low-dimensional architectures frequently exhibit novel functional properties. In current work, NiO nanobelts with well-defined morphologies and uniform size have been successfully synthesized via a facile hydrothermal method. Furthermore, a novel growth mechanism of NiO nanobelts has been proposed in detail. Surprisingly, it is worth mentioning that the sodium oxalate is of great benefit to the formation of NiO one-dimensional nanostructures and plays a vital role on tailoring morphologies of nanobelts on the basis of further comparative experiments. Such a synthetic way may open up an avenue to prepare some other oxides. & 2015 Elsevier B.V. All rights reserved.
Keywords: Nanostructures Formation mechanism Ceramics Functional Crystal Growth
1. Introduction As a significant p-type semiconductor with wide band gap energy in the range of 3.6–4.0 eV, nickel oxide (NiO) has captured a great deal of interests in varieties of application fields [1–3], such as full cell electrodes [4], solar cell [5], catalysts [6], photovoltaic devices [7] and gas sensors [8]. In the past few years, it has been acknowledged that synthesis of multifarious nanomaterials with novel morphologies has attracted massive attentions owing to their unique architectures and extensive potential applications [9–11]. Notably, one-dimensional nanostructures of metal oxide may exhibit unique functional properties, which cannot be realized in their individual nanobulks, due to the controlled motion of electron in limited dimensions, and thereby are of the great interest in current research. As is known to all, massive efforts have been developed to synthesize NiO nanomaterials with lowdimensional architectures, such as chemical precipitation [12], sol–gel method [13], ultrasonic technique [14] and hydrothermal method [15]. Compared with other synthetic techniques, hydrothermal method is one of the most effective routes due to its low cost, convenient operation, mild condition, improvement of the thermal stability and functional properties of NiO nanomaterials [16,17], which hence applied to our experiment. Although considerable works have been carrying out to fabricate NiO onedimensional architectures, it still remains a huge challenge to synthesize NiO nanobelts with well-defined morphologies and excellent dispersion. Moreover, it has been the first observation n
Corresponding author. Tel: þ 86 2365 102 465. E-mail address: [email protected] (W. Zeng).
http://dx.doi.org/10.1016/j.matlet.2015.04.149 0167-577X/& 2015 Elsevier B.V. All rights reserved.
that transformation from NiO nanobelts (1D) to nanosheets (2D) can be triggered by reducing of the dose of sodium oxalate, indicating that sodium oxalate played a key role on the formation of the NiO nanobelts (1D), which has been systematically investigated in our work. In current work, NiO nanobelts have been successfully synthesized via sodium oxalate assisted hydrothermal. The as-obtained powders were characterized in terms of structures and morphologies. Furthermore, a novel formation mechanism of NiO nanobelts was proposed and the effects of sodium oxalate on the growth of NiO nanobelts were investigated in detail.
2. Experimental All the chemicals were of analytic purity and used directly without any further purification. In a typical hydrothermal procedure, 0.474 g of nickel chloride hexahydrate (NiCl2 6H2O) and 0.044 g sodium oxalate (Na2C2O4) were dissolved in 18 ml of distilled water. And then 30 ml ethylene glycol (EG) was introduced into the breaker under vigorous stirring for 30 min. After that, the obtained solution was transferred into a Teflon-lined stainless steel autoclave (50 ml) and sealed 18 1C for 12 h in an oven. When the hydrothermal process was finished, the heated autoclave cooled down to room temperature naturally. The products were obtained by centrifugation and washed with distilled water and ethanol for 3 times, respectively. And then the prepared samples were dried at 60 1C for 24 h to obtain the powders. Finally, the powders were heated to 400 1C with a rate of 1.0 1C min 1 and then calcined at 400 1C for 2 h. The other NiO nanostructures were
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S. Cao et al. / Materials Letters 156 (2015) 25–27
synthesized just by varying the amount of sodium oxalate: 0.132 g, 0.09 g and 0 g, respectively. The phase purity and structure of as-prepared samples were characterized by X-ray diffraction (XRD) using a Rigaku D/Max1200X diffractometry with CuKα radiation operated at 30 kV and 100 mA. Morphologies and architectures of the NiO nanomaterials were investigated by using a Nova field emission scanning electronic microscopy (FE-SEM).
3. Results and discussion To confirm structure and purity of the prepared precursors and final products, XRD patterns of as-prepared samples were first performed in Fig. 1(a) and (b). As illustrated in Fig. 1(a)I–III, all the diffraction peaks of the precursors can be well index to the standard spectrum (JCPDS Card no. 25-0581), indicating that these products must be the pure NiC2O4 2H2O. Whereas the sheet-like samples proved to be the pure Ni(OH)2, as illustrated in Fig. 1(a)IV. Fig. 1 (b) displays the XRD patterns of the final products. Compared to the standard spectrum (JCPDS Card no. 04-0835), it can be seen that the diffraction peaks of the final products can be well indexed to the NiO, indicating that there was no other impurities. Microstructures and morphologies of the as-obtained samples were characterized by FE-SEM observations. Fig. 2(a)–(d) illustrates the NiC2O4 2H2O nanostructures with various amount of sodium oxalate. Fig. 2 (a) illustrates the SEM images of the NiC2O4 2H2O nanobelts synthesized by using 0.132 g sodium oxalate, with length and diameter of 4 μm and 80 nm and gathered to form bundles to a certain extent. When the dose of sodium oxalate was 0.09 g, the NiC2O4 2H2O nanobelts possessing the length and diameter of 6 μm and 100 nm were obtained, respectively, as shown in Fig. 2 (b). Keep on decreasing the amount of sodium oxalate to 0.044 g, it can be obviously observed that NiC2O4 2H2O nanobelts with the length and diameter of 8 μm and 150 nm presented more uniformly, separated and straight morphologies, and a few nanosheets distributing in the nanobelts can be easily noticed, as shown in Fig. 2(c). However, once the sodium oxalate even out of use, the
NiC2O4 2H2O nanosheets (2D) possessing the diameter of 500 nm were largely obtained instead of nanobelts, as shown in Fig. 2(d). And the SEM images of NiO nanostructures are illustrated in Fig. 3 (a)–(d), which is similar to the morphologies of the precursors. Hence, in accordance with the experimental observations, it can be concluded that introduction of sodium oxalate plays a vital role on promoting the formation of NiC2O4 2H2O one-dimensional architectures and NiC2O4 2H2O nanobelts can be tailored to grow more uniform and dispersed by controlling the amount of sodium oxalate. The figure illustrates the NiO low-dimensional architectures obtained by calcining NiC2O4 2H2O at 400 1C. On the basis of the experimental observations and analysis, a plausible formation mechanism for the morphologies evolution of the NiO nanobelts was proposed, as illustrated in Fig. 4. In our investigations, the sodium oxalate was a key factor in the formation and tailoring morphologies of the NiO nanobelts (1D). When sodium oxalate was introduced, Ni2 þ ions and C2O24 can be illustrated as a polymer type ribbon owing to the strong complexation between Ni2 þ ions and C2O24 , as shown in step 2 of Fig. 4. It has been reported that EG served as a ligand to Ni and suppressed the formation of (101), (101), (010) and (010) planes, which were paralleled to [101] direction [18], as shown in step 3 of Fig. 4. Besides the actions of EG, based on an oriented attachment, the adjacent intermediate nanostructures were selfassembled along the same crystallographic resulting from the reduction of high energy surface [19,20]. Therefore, with reaction time went by, substantial architectures identical to the step 3 were connected with each other along [101] directions in the presence of EG, as shown in step 4 of Fig. 4 and the NiO nanobelts were obtained by subsequent calcination. In addition, the hydrogen bond between EG molecule may be the main cause of the formation of nanobelt bundles [21]. However, it is surprisingly that the NiO nanosheets (2D) were largely synthesized instead of nanobelts (1D) without introducing the sodium oxalate, mainly because there were no NiC2O4 2H2O polymer type ribbons mentioned above but massive Ni(OH)2 nuclei obtained. And then the Ni(OH)2 nanocrystal aggregated and grew to form the nanosheets in the presence of EG to eliminate the surface energy.
Fig. 1. XRD pattern of the as-prepared products: (a) NiC2O4 2H2O nanobelts varying the amount of sodium oxalate: (I) 0.132 g, (II) 0.09 g, (III) 0.044 g and (IV) Ni(OH)2 nanosheets; (b) NiO nanostructures (I)–(IV) corresponding to (a) (I)–(IV).
Fig. 2. SEM images of the as-prepared precursors with various amounts of sodium oxalate: (a) 0.132 g; (b) 0.09 g; (c) 0.044 g and (d) 0 g.
S. Cao et al. / Materials Letters 156 (2015) 25–27
27
Fig. 3. SEM images of the as-prepared NiO low-dimensional architectures with various amounts of sodium oxalate: (a) 0.132 g; (b) 0.09 g; (c) 0.044 g and (d) 0 g.
Fig. 4. Schematic illustration of the evolution processes of the NiO nanobelts.
4. Conclusion In this letter, NiO nanobelts with uniform size and well-defined morphologies have been successfully synthesized via a sodium oxalate assisted hydrothermal route and subsequent thermal calcination. A plausible formation mechanism of NiO nanobelts was proposed. Furthermore, the effect of sodium oxalate on the morphologies has been investigated in detail. It was amazingly found that NiO nanobelts can be more uniform and dispersed by controlling the dose of sodium oxalate, which also play a critical role on the formation of one-dimensional architectures. Acknowledgments This work was supported in part by the National Natural Science Foundation of China, China (No. 51202302, 51277185 and 11332013), the Fundamental Research Funds for the Central Universities (No. 106112015CDJXY130013), 6th Student Research Training Program of the Chongqing University, China (CQU-SRTP2014155) and the fund of Chongqing University's Large-scale Equipment (No. 2013121521). References [1] Lin LY, Liu TM, Miao B, Zeng W. Mater Res Bull 2013;48:449–54. [2] Yang HJ, Cao WQ, Zhang DQ, Su TJ, Shi HL, Wang WZ, et al. Acs Appl Mater Interfaces 2015;7:7073–7.
[3] Yang HJ, Cao MS, Li Y, Shi HL, Hou ZL, Fang XY, et al. Adv Opt Mater 2014;2:214–9. [4] Yao MM, Hu ZH, Xu ZJ, Liu YF, Liu PP, Zhang Q. Electrochim Acta 2015;158:96–104. [5] Lin YC, Chen YT, Yao PC J. Power Sources 2013;240:705–12. [6] Zhu HB, Dong HL, Paco L, Youssef S, Valerie C, Basset JM. Catal Today 2014;228:58–64. [7] Wang ZY, Lee SH, Kim DH, Kim JH, Park JG. Sol Energy Mater Sol Cell 2010;94:1591–6. [8] Lin LY, Liu TM, Miao B, Zeng W. Mater Lett 2013;102–103:43–6. [9] Zhang Q, Liu HX, Li HL, Liu Y, Zhang HY, Li TD. Appl Surf Sci 2015;328:525–30. [10] Zeng W, Miao B, Zhou Q, Lin LY. Physica E 2013;47:116–21. [11] Wang Q, Zhang CY, Shan WF, Xing LL, Xue XY. Mater Lett 2014;118:66–8. [12] Wang SF, Shi LY, Feng X, Ma SR. Mater Lett 2007;61:1549–51. [13] Wang N, Liu CQ, Wen B, Wang HL, Liu SM, Chai WP. Mater Lett 2014;122:269–72. [14] Al-Hazmi F, Al-Harbi T, Mahmoud WE. Mater Lett 2012;86:28–30. [15] Zhao B, Song JS, Fang T, Liu P, Jiao Z, Zhang HJ, et al. Mater Lett 2012;67: 24–27. [16] Wu QS, Shen Y, Li LY, Cao M, Gu F, Wang LJ. Appl Surf Sci 2013;276:411–6. [17] Wang L, Hao YJ, Zhao Y, Lai QY, Xu XY J. Solid State Chem 2010;183:2576–81. [18] Miao B, Zeng W, Lin LY, Xu S. 2013; 52:40–45. [19] Lu R, Yuan J, Shi HL, Li B, Wang WZ, Wang DW, et al. CrystEngComm 2013;15:3984–91. [20] Zhao YN, Cao MS, Jin HB, Shi XL, Li X, Agathopoulos S. J Nanosci Nanotechnol 2006;6:2525–8. [21] Liu B, Yang HQ, Zhao H, An LJ, Zhang LH, Shi RY, et al. Sens Actuators B: Chem 2011;156:251–62.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Hydrothermal synthesis of NiO nanobelts and the effect of sodium oxalate Shengkai Cao, Wen Zeng n, Tianmin Li, Jun Gong, Zhenjie Zhu College of Materials Science and Engineering, Chongqing University, Chongqing, China
art ic l e i nf o
a b s t r a c t
Article history: Received 16 March 2015 Accepted 29 April 2015 Available online 7 May 2015
Nanomaterials with low-dimensional architectures frequently exhibit novel functional properties. In current work, NiO nanobelts with well-defined morphologies and uniform size have been successfully synthesized via a facile hydrothermal method. Furthermore, a novel growth mechanism of NiO nanobelts has been proposed in detail. Surprisingly, it is worth mentioning that the sodium oxalate is of great benefit to the formation of NiO one-dimensional nanostructures and plays a vital role on tailoring morphologies of nanobelts on the basis of further comparative experiments. Such a synthetic way may open up an avenue to prepare some other oxides. & 2015 Elsevier B.V. All rights reserved.
Keywords: Nanostructures Formation mechanism Ceramics Functional Crystal Growth
1. Introduction As a significant p-type semiconductor with wide band gap energy in the range of 3.6–4.0 eV, nickel oxide (NiO) has captured a great deal of interests in varieties of application fields [1–3], such as full cell electrodes [4], solar cell [5], catalysts [6], photovoltaic devices [7] and gas sensors [8]. In the past few years, it has been acknowledged that synthesis of multifarious nanomaterials with novel morphologies has attracted massive attentions owing to their unique architectures and extensive potential applications [9–11]. Notably, one-dimensional nanostructures of metal oxide may exhibit unique functional properties, which cannot be realized in their individual nanobulks, due to the controlled motion of electron in limited dimensions, and thereby are of the great interest in current research. As is known to all, massive efforts have been developed to synthesize NiO nanomaterials with lowdimensional architectures, such as chemical precipitation [12], sol–gel method [13], ultrasonic technique [14] and hydrothermal method [15]. Compared with other synthetic techniques, hydrothermal method is one of the most effective routes due to its low cost, convenient operation, mild condition, improvement of the thermal stability and functional properties of NiO nanomaterials [16,17], which hence applied to our experiment. Although considerable works have been carrying out to fabricate NiO onedimensional architectures, it still remains a huge challenge to synthesize NiO nanobelts with well-defined morphologies and excellent dispersion. Moreover, it has been the first observation n
Corresponding author. Tel: þ 86 2365 102 465. E-mail address: [email protected] (W. Zeng).
http://dx.doi.org/10.1016/j.matlet.2015.04.149 0167-577X/& 2015 Elsevier B.V. All rights reserved.
that transformation from NiO nanobelts (1D) to nanosheets (2D) can be triggered by reducing of the dose of sodium oxalate, indicating that sodium oxalate played a key role on the formation of the NiO nanobelts (1D), which has been systematically investigated in our work. In current work, NiO nanobelts have been successfully synthesized via sodium oxalate assisted hydrothermal. The as-obtained powders were characterized in terms of structures and morphologies. Furthermore, a novel formation mechanism of NiO nanobelts was proposed and the effects of sodium oxalate on the growth of NiO nanobelts were investigated in detail.
2. Experimental All the chemicals were of analytic purity and used directly without any further purification. In a typical hydrothermal procedure, 0.474 g of nickel chloride hexahydrate (NiCl2 6H2O) and 0.044 g sodium oxalate (Na2C2O4) were dissolved in 18 ml of distilled water. And then 30 ml ethylene glycol (EG) was introduced into the breaker under vigorous stirring for 30 min. After that, the obtained solution was transferred into a Teflon-lined stainless steel autoclave (50 ml) and sealed 18 1C for 12 h in an oven. When the hydrothermal process was finished, the heated autoclave cooled down to room temperature naturally. The products were obtained by centrifugation and washed with distilled water and ethanol for 3 times, respectively. And then the prepared samples were dried at 60 1C for 24 h to obtain the powders. Finally, the powders were heated to 400 1C with a rate of 1.0 1C min 1 and then calcined at 400 1C for 2 h. The other NiO nanostructures were
26
S. Cao et al. / Materials Letters 156 (2015) 25–27
synthesized just by varying the amount of sodium oxalate: 0.132 g, 0.09 g and 0 g, respectively. The phase purity and structure of as-prepared samples were characterized by X-ray diffraction (XRD) using a Rigaku D/Max1200X diffractometry with CuKα radiation operated at 30 kV and 100 mA. Morphologies and architectures of the NiO nanomaterials were investigated by using a Nova field emission scanning electronic microscopy (FE-SEM).
3. Results and discussion To confirm structure and purity of the prepared precursors and final products, XRD patterns of as-prepared samples were first performed in Fig. 1(a) and (b). As illustrated in Fig. 1(a)I–III, all the diffraction peaks of the precursors can be well index to the standard spectrum (JCPDS Card no. 25-0581), indicating that these products must be the pure NiC2O4 2H2O. Whereas the sheet-like samples proved to be the pure Ni(OH)2, as illustrated in Fig. 1(a)IV. Fig. 1 (b) displays the XRD patterns of the final products. Compared to the standard spectrum (JCPDS Card no. 04-0835), it can be seen that the diffraction peaks of the final products can be well indexed to the NiO, indicating that there was no other impurities. Microstructures and morphologies of the as-obtained samples were characterized by FE-SEM observations. Fig. 2(a)–(d) illustrates the NiC2O4 2H2O nanostructures with various amount of sodium oxalate. Fig. 2 (a) illustrates the SEM images of the NiC2O4 2H2O nanobelts synthesized by using 0.132 g sodium oxalate, with length and diameter of 4 μm and 80 nm and gathered to form bundles to a certain extent. When the dose of sodium oxalate was 0.09 g, the NiC2O4 2H2O nanobelts possessing the length and diameter of 6 μm and 100 nm were obtained, respectively, as shown in Fig. 2 (b). Keep on decreasing the amount of sodium oxalate to 0.044 g, it can be obviously observed that NiC2O4 2H2O nanobelts with the length and diameter of 8 μm and 150 nm presented more uniformly, separated and straight morphologies, and a few nanosheets distributing in the nanobelts can be easily noticed, as shown in Fig. 2(c). However, once the sodium oxalate even out of use, the
NiC2O4 2H2O nanosheets (2D) possessing the diameter of 500 nm were largely obtained instead of nanobelts, as shown in Fig. 2(d). And the SEM images of NiO nanostructures are illustrated in Fig. 3 (a)–(d), which is similar to the morphologies of the precursors. Hence, in accordance with the experimental observations, it can be concluded that introduction of sodium oxalate plays a vital role on promoting the formation of NiC2O4 2H2O one-dimensional architectures and NiC2O4 2H2O nanobelts can be tailored to grow more uniform and dispersed by controlling the amount of sodium oxalate. The figure illustrates the NiO low-dimensional architectures obtained by calcining NiC2O4 2H2O at 400 1C. On the basis of the experimental observations and analysis, a plausible formation mechanism for the morphologies evolution of the NiO nanobelts was proposed, as illustrated in Fig. 4. In our investigations, the sodium oxalate was a key factor in the formation and tailoring morphologies of the NiO nanobelts (1D). When sodium oxalate was introduced, Ni2 þ ions and C2O24 can be illustrated as a polymer type ribbon owing to the strong complexation between Ni2 þ ions and C2O24 , as shown in step 2 of Fig. 4. It has been reported that EG served as a ligand to Ni and suppressed the formation of (101), (101), (010) and (010) planes, which were paralleled to [101] direction [18], as shown in step 3 of Fig. 4. Besides the actions of EG, based on an oriented attachment, the adjacent intermediate nanostructures were selfassembled along the same crystallographic resulting from the reduction of high energy surface [19,20]. Therefore, with reaction time went by, substantial architectures identical to the step 3 were connected with each other along [101] directions in the presence of EG, as shown in step 4 of Fig. 4 and the NiO nanobelts were obtained by subsequent calcination. In addition, the hydrogen bond between EG molecule may be the main cause of the formation of nanobelt bundles [21]. However, it is surprisingly that the NiO nanosheets (2D) were largely synthesized instead of nanobelts (1D) without introducing the sodium oxalate, mainly because there were no NiC2O4 2H2O polymer type ribbons mentioned above but massive Ni(OH)2 nuclei obtained. And then the Ni(OH)2 nanocrystal aggregated and grew to form the nanosheets in the presence of EG to eliminate the surface energy.
Fig. 1. XRD pattern of the as-prepared products: (a) NiC2O4 2H2O nanobelts varying the amount of sodium oxalate: (I) 0.132 g, (II) 0.09 g, (III) 0.044 g and (IV) Ni(OH)2 nanosheets; (b) NiO nanostructures (I)–(IV) corresponding to (a) (I)–(IV).
Fig. 2. SEM images of the as-prepared precursors with various amounts of sodium oxalate: (a) 0.132 g; (b) 0.09 g; (c) 0.044 g and (d) 0 g.
S. Cao et al. / Materials Letters 156 (2015) 25–27
27
Fig. 3. SEM images of the as-prepared NiO low-dimensional architectures with various amounts of sodium oxalate: (a) 0.132 g; (b) 0.09 g; (c) 0.044 g and (d) 0 g.
Fig. 4. Schematic illustration of the evolution processes of the NiO nanobelts.
4. Conclusion In this letter, NiO nanobelts with uniform size and well-defined morphologies have been successfully synthesized via a sodium oxalate assisted hydrothermal route and subsequent thermal calcination. A plausible formation mechanism of NiO nanobelts was proposed. Furthermore, the effect of sodium oxalate on the morphologies has been investigated in detail. It was amazingly found that NiO nanobelts can be more uniform and dispersed by controlling the dose of sodium oxalate, which also play a critical role on the formation of one-dimensional architectures. Acknowledgments This work was supported in part by the National Natural Science Foundation of China, China (No. 51202302, 51277185 and 11332013), the Fundamental Research Funds for the Central Universities (No. 106112015CDJXY130013), 6th Student Research Training Program of the Chongqing University, China (CQU-SRTP2014155) and the fund of Chongqing University's Large-scale Equipment (No. 2013121521). References [1] Lin LY, Liu TM, Miao B, Zeng W. Mater Res Bull 2013;48:449–54. [2] Yang HJ, Cao WQ, Zhang DQ, Su TJ, Shi HL, Wang WZ, et al. Acs Appl Mater Interfaces 2015;7:7073–7.
[3] Yang HJ, Cao MS, Li Y, Shi HL, Hou ZL, Fang XY, et al. Adv Opt Mater 2014;2:214–9. [4] Yao MM, Hu ZH, Xu ZJ, Liu YF, Liu PP, Zhang Q. Electrochim Acta 2015;158:96–104. [5] Lin YC, Chen YT, Yao PC J. Power Sources 2013;240:705–12. [6] Zhu HB, Dong HL, Paco L, Youssef S, Valerie C, Basset JM. Catal Today 2014;228:58–64. [7] Wang ZY, Lee SH, Kim DH, Kim JH, Park JG. Sol Energy Mater Sol Cell 2010;94:1591–6. [8] Lin LY, Liu TM, Miao B, Zeng W. Mater Lett 2013;102–103:43–6. [9] Zhang Q, Liu HX, Li HL, Liu Y, Zhang HY, Li TD. Appl Surf Sci 2015;328:525–30. [10] Zeng W, Miao B, Zhou Q, Lin LY. Physica E 2013;47:116–21. [11] Wang Q, Zhang CY, Shan WF, Xing LL, Xue XY. Mater Lett 2014;118:66–8. [12] Wang SF, Shi LY, Feng X, Ma SR. Mater Lett 2007;61:1549–51. [13] Wang N, Liu CQ, Wen B, Wang HL, Liu SM, Chai WP. Mater Lett 2014;122:269–72. [14] Al-Hazmi F, Al-Harbi T, Mahmoud WE. Mater Lett 2012;86:28–30. [15] Zhao B, Song JS, Fang T, Liu P, Jiao Z, Zhang HJ, et al. Mater Lett 2012;67: 24–27. [16] Wu QS, Shen Y, Li LY, Cao M, Gu F, Wang LJ. Appl Surf Sci 2013;276:411–6. [17] Wang L, Hao YJ, Zhao Y, Lai QY, Xu XY J. Solid State Chem 2010;183:2576–81. [18] Miao B, Zeng W, Lin LY, Xu S. 2013; 52:40–45. [19] Lu R, Yuan J, Shi HL, Li B, Wang WZ, Wang DW, et al. CrystEngComm 2013;15:3984–91. [20] Zhao YN, Cao MS, Jin HB, Shi XL, Li X, Agathopoulos S. J Nanosci Nanotechnol 2006;6:2525–8. [21] Liu B, Yang HQ, Zhao H, An LJ, Zhang LH, Shi RY, et al. Sens Actuators B: Chem 2011;156:251–62.