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Preparation and characterization of hollow glass microspheres–cobalt ferrite core-shell particles based on homogeneous coprecipitation
Materials Letters 65 (2011) 929–932
Contents lists available at ScienceDirect
Materials Letters j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m a t l e t
Preparation and characterization of hollow glass microspheres–cobalt ferrite core-shell particles based on homogeneous coprecipitation Jianhua Liu ⁎, Dun You, Mei Yu, Songmei Li School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, PR China
a r t i c l e
i n f o
Article history: Received 11 October 2010 Accepted 23 October 2010 Available online 31 October 2010 Keywords: Hollow glass microspheres Homogeneous coprecipitation CoFe2O4 Core-shell
a b s t r a c t Hollow glass microspheres–CoFe2O4 (HGMs-CF) core-shell particles were successfully synthesized directly by using the homogeneous coprecipitation method at 90 °C without calcination. The morphology, composition, microstructure and the magnetic property of the samples were characterized by SEM, XRD, EDX and VSM, respectively. The results showed that the HGMs-CF core-shell particles exhibited smooth, compact and continuous CoFe2O4 coating on the surface of the HGMs. The Fe/Co atom ratio of the CoFe2O4 coating was 2.2, saturation magnetization (Ms) and coercivity (Hc) of the samples were 46 emu/g and 612 Oe, respectively. It was suggested that this method could be applied to the scale industry production for high purity products. © 2010 Elsevier B.V. All rights reserved.
1. Introduction Ferrites of the spinel type MFe2O4 (M is a divalent metal cation) are magnetic materials with cubic spinel structure, which have been extensively used in various technological applications in the past decades [1,2]. Among them, CoFe2O4 (CF) are widely studied in electronic devices [3], ferrofluids [4], magnetic drug delivery [5], and microwave devices [6] due to its excellent magnetic properties [7]. However, the large density restricts its widely application [8]. Aiming to reduce density, it may be one of the effective way to synthesize CoFe2O4 on light substrate particles [9], in order to obtain core-shell particles [10]. Core-shell particles have been synthesized by a number of methods, including microemulsion [11], sol–gel techniques [12], hydrothermal synthesis [13], solvothermal [14], coprecipitation [15] and electrochemical synthesis [16]. Among these methods, coprecipitation is an easy and versatile technique [17]. However, the conventional coprecipitation method usually uses a strong base as precipitant [18], which makes it difficult to control the supersaturation properly and consequently leads to form discontinuous shell and plenty of free particles impurities without core-shell structure. This shortcoming may be overcome by the homogeneous coprecipitation method in which the precipitants such as urea release OH−gradually at elevated temperature [19]. Thus, a better control of the supersaturation could be achieved and the impurities could be suppressed greatly [20]. CoFe2O4 has been synthesized by the coprecipitation method using either Fe3+ or Fe2+ as reactant , respectively [7,21]. However, the
⁎ Corresponding author. Tel./fax: +86 10 82317103. E-mail address: [email protected] (J. Liu). 0167-577X/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2010.10.070
employment of Fe3+ usually requires the subsequent calcination (400–600 °C) [22]. while CoFe2O4 could form directly by using Fe2+ as reactant in the aqueous solution under 100 °C without further calcination process [23]. The oxidation rate of Fe2+ to Fe3+ is essential for the cobalt ferrite formation [24]. Hollow glass microspheres (HGMs) were usually used as “core” due to its low density. Hollow glass microspheres–CoFe2O4 (HGMsCF) core-shell particles were synthesized [25], but a further calcination process up to 600 °C was required. In our previous works, light multi-functional core-shell particles have been synthesized based on HGMs [26,27]. In this study, the light HGMs-CF coreshell particles were obtained with minimized impurities by the homogeneous coprecipitation method at 90 °C without calcination. 2. Materials and methods 2.1. Materials All the reagents were of analytical grade and used as received without further purification. Cobalt chloride [CoCl2·6H2O], ferrous chloride [FeCl2·4H2O], urea ((NH2)2CO), and hydrochloric acid (HCl) were purchased from Beijing Chemical Corporation (China). 2.2. Sample preparation The HGMs-CF core-shell particles were produced by homogenous coprecipitation in which urea was selected as the precipitant. First, 0.12 mol urea and 72 μl HCl were dissolved in 100 ml deionized water with magnetic stirring at room temperature, after that N2 was passing through the above solution to remove the O2 for 30 min; second, stoichiometric ferrous chloride (4 mmol) and cobalt chloride (2 mmol)
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J. Liu et al. / Materials Letters 65 (2011) 929–932
were added under magnetic stirring and reaction solution was obtained. Then, 0.1 g HGMs were dispersed into the reaction solution. The resulting suspension was refluxed at 90 °C in a silicon oil bath for 1 hour. After that, 10 ml KNO3 (0.4 mol/L) was added dropwise and followed by refluxing at 90 °C for another 1 hour with stirring. All the steps of the reaction mentioned above were carried out under N2 atmosphere. The resulting precipitates were washed with deionized water and then filtered. The washing and filtration were repeated several times until the discard water was free of chlorides, which was checked by an AgNO3 solution. The washed powders dried at 80 °C for 12 h. Finally, the HGMs-CF core-shell particles were obtained. 2.3. Characterization The surface morphology and chemical composition of the samples were observed by using scanning electron microscope (SEM, Apollo300, CamScan) and energy dispersion X-ray (EDX, INCA PentaFETx3,
Oxford), respectively. The structure was analyzed by X-ray diffractometer (XRD, D/max 2200PC, RigaKu) with Cu Ka radiation. A vibratingsample magnetometer (VSM, BHV-50HTI, Riken Denshi) was used to study the magnetic properties of the samples. 3. Results and discussion Fig. 1 presents the SEM micrographs of the samples at different magnifications. As shown in Fig. 1a, the diameter of the HGMs is in the range of 10–80 μm. It is found that the surface of the HGMs is smooth. After the coprecipitation reaction, it is obvious that a coating is grown on the surface of the HGMs and the core-shell structure is obtained. The coating is encapsulated completely and uniformly. Furthermore, nearly no free particle impurities of none core-shell structure appears in the sample, which is attributed to the homogeneous coprecipitation method in which OH− is released gradually, and consequently the heterogeneous nucleation and growth are occurred during the
Fig. 1. SEM micrographs of samples. (a), (b) and (c), HGMs; (d), (e) and (f), HGMs-CF core-shell particles.
J. Liu et al. / Materials Letters 65 (2011) 929–932
931
Fig. 2. EDX of the CF coating of the HGMs-CF core-shell particles.
reaction [28]. The reactions are shown in Eqs. (1) and (2). Compared with Pang's method [25], our synthetic strategy needs no further calcination process and the CoFe2O4 coating could form directly in the aqueous solution. Fig. 4. Magnetization hysteresis of as-synthesized HGMs-CF core-shell particles sample. þ
−
COðNH2 Þ2 + H2 O→NH4 + CO2 + OH 2+
Co
2+
+ 2Fe
+ 6OH
−
+ 1 = 2O2 →CoFe2 O4 + 3H2 O
ð1Þ ð2Þ
Fig. 2 shows the EDX analysis of the CF coating of the HGMs-CF core-shell particles. It appears that Fe and Co exist in the coating, which suggests that both Fe and Co are coprecipitated on the surface of the HGMs. Furthermore, the Fe/Co atom ratio of the sample is 2.2, which is approximately consistent with the stoichiometric ratio of the cobalt ferrite. The elements of Ca, Na and Si are attributed to the HGMs itself. The X-ray diffraction pattern of the samples are shown in Fig. 3. Curve (a) is mainly composed of broaden peaks around 10–25° of 2θ, which suggests the amorphous structure of the HGMs. In Curve (b), peaks appeared at 2 theta = 30.1°, 35.2°, 37.1°, 43.0°, 53.4°, 56.9° and 62.6° ascribing to CoFe2O4 (220), (311), (222), (400), (422), (511) and (440) (JCPDS No.22-1086), indicating the formation of CoFe2O4. Besides, the broaden diffraction peaks of HGMs also exist in the range of 10–25˚in curve (b). Based on the result of the SEM, EDX and XRD, we draw the conclusion that the HGMs-CF core-shell particles with smooth, compact and continuous CoFe2O4 coatings are obtained by homogeneous coprecipitation at 90 °C without calcination. Magnetization measurement of the sample is carried out with a field scan of ±1.0 kOe at room temperature and the hysteresis loop of
the sample is shown in Fig. 4. This curve is typical for a soft-magnetic material. The saturation magnetization Ms and coercivity are determined to be 46 emu/g and 612 Oe, respectively. The saturation magnetization Ms is lower than the theory value (72 emu/g) of CoFe2O4 [29], which may be attributed to none-magnetic HGMs. The inset in Fig. 4 is a photo of HGMs-CF core-shell particles in ethanol with and without an external magnetic field. It is clear that the HGMsCF core-shell particles are all floating under no external magnetic field condition, which implies the greatly reduced density compared to that of theoretical bulk of CoFe2O4 (5.20 g/cm3) [8]. On the other hand, it can also be found that the HGMs-CF core-shell particles exhibit an obvious magnetic response when the external magnetic field is added, reflecting the good magnetic properties of the HGMs-CF core-shell particles visually. 4. Conclusions In summary, HGMs-CF core-shell particles have been successfully synthesized by the homogeneous coprecipitation method at 90 °C without calcination. The obtained HGMs-CF core-shell particles exhibit smooth, compact and continuous CoFe2O4 coatings on the surface of the HGMs. The saturation magnetization (Ms) and the coercivity (Hc) of as-sample were 46 emu/g and 612 Oe, respectively. The main advantage of this synthetic strategy is that the HGMs-CF core-shell particles can form directly in the aqueous solution at low temperature (90 °C) and no further calcination is needed, as well as that the free particles impurities without core-shell structure could been greatly suppressed. We suggest that this method can be applied to the scale industry production for high purity products. Acknowledgement The authors gratefully acknowledge the financial support for this work from National Natural Science Foundation of China (51001007). References
Fig. 3. XRD patterns of the HGMs (a), and HGMs-CF core-shell particles (b).
[1] Jeong U, Teng XW, Wang Y, Yang H, Xia YN. Adv Mater 2007;19:33–60. [2] Park J, Joo J, Kwon SG, Jang Y, Hyeon T. Angew Chem Int Ed 2007;46:4630–60. [3] Zhou ZP, Zhang Y, Wang ZY, Wei W, Tang WF, Shi J, et al. Appl Surf Sci 2008;254: 6972–5. [4] Morais PC, Santos RL, Pimenta ACM, Azevedo RB, Lima ECD. Thin Solid Films 2006;515:266–70. [5] Kim DH, Nikles DE, Johnson DT, Brazel CS. J Magn Magn Mater 2008;320:2390–6. [6] Allaeys JF, Mage JC. Ieee Mtt S Int Microw Symp Dig 2007;1-6:702–5. [7] Maaz K, Mumtaz A, Hasanain SK, Ceylan A. J Magn Magn Mater 2007;308:289–95. [8] Cannas C, Ardu A, Musinu A, Peddis D, Piccaluga G. Chem Mater 2008;20:6364–71.
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J. Liu et al. / Materials Letters 65 (2011) 929–932
[9] Li YX, Yin DP, Wang ZQ, Li B, Xue G. Colloids Surf Physicochemical Eng Aspects 2009;339:100–5. [10] Wang CC, Chen IH, Lin CR, Chen CY. Advanced manufacture. Focusing New Emerg Technol 2008;594:150–4. [11] Yang YH, Jing LH, Yu XL, Yan DD, Gao MY. Chem Mater 2007;19:4123–8. [12] Liu M, Li X, Imrane H, Chen YJ, Goodrich T, Cai ZH, et al. Appl Phys Lett 2007:90. [13] Plank NOV, Snaith HJ, Ducati C, Bendall JS, Schmidt-Mende L, Welland ME. Nanotechnology 2008:19. [14] Deng D, Lee JY. Chem Mater 2008;20:1841–6. [15] Gole A, Stone JW, Gemmill WR, zur Loye HC, Murphy CJ. Langmuir 2008;24: 6232–7. [16] Hu XG, Dong SJ. J Mater Chem 2008;1279-95:1279–95. [17] Cozzoli PD, Pellegrino T, Manna L. Chem Soc Rev 2006;35:1195–208. [18] Zhao DL, Zhang HL, Zeng XW, Xia QS, Tang JT. Biomed Mater 2006;1:198–201.
[19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29]
Jia G, Yang M, Song YH, You HP, Zhang HJ. Cryst Growth Des 2009;9:301–7. Jia G, You HP, Liu K, Zheng YH, Guo N, Zhang HJ. Langmuir 2010;26:5122–8. Shaheen WM. Mater Chem Phys 2007;101:182–90. Chia CHSZ, Yusoff M, Goh SC, Haw CY, Sh. Ahmadi NMH, Lim HN. Ceram Int 2010;36:605–9. Wang J, Deng T, Dai YJ. J Alloy Comp 2006;419:155–61. Morgan BE, Lahav O, Loewenthal RE. Environ Sci Technol 2005;39:7678–83. Pang XF, Wu YF, Yang HB, Zhu HY, Xu J, Li X, Zou GT. Mater Res Bull 2009;44: 360–3. Liu JH, Wei J, Li SM. Mater Lett 2007;61:1529–32. Wei J, Liu JH, Li SM. J Magn Magn Mater 2007;312:414–7. Matijevic E. Langmuir 1994;10:8–16. Ayyappan S, Mahadevan S, Chandramohan P, Srinivasan MP, Philip J, Raj B. J Phys Chem C 2010;114:6334–41.
Contents lists available at ScienceDirect
Materials Letters j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m a t l e t
Preparation and characterization of hollow glass microspheres–cobalt ferrite core-shell particles based on homogeneous coprecipitation Jianhua Liu ⁎, Dun You, Mei Yu, Songmei Li School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, PR China
a r t i c l e
i n f o
Article history: Received 11 October 2010 Accepted 23 October 2010 Available online 31 October 2010 Keywords: Hollow glass microspheres Homogeneous coprecipitation CoFe2O4 Core-shell
a b s t r a c t Hollow glass microspheres–CoFe2O4 (HGMs-CF) core-shell particles were successfully synthesized directly by using the homogeneous coprecipitation method at 90 °C without calcination. The morphology, composition, microstructure and the magnetic property of the samples were characterized by SEM, XRD, EDX and VSM, respectively. The results showed that the HGMs-CF core-shell particles exhibited smooth, compact and continuous CoFe2O4 coating on the surface of the HGMs. The Fe/Co atom ratio of the CoFe2O4 coating was 2.2, saturation magnetization (Ms) and coercivity (Hc) of the samples were 46 emu/g and 612 Oe, respectively. It was suggested that this method could be applied to the scale industry production for high purity products. © 2010 Elsevier B.V. All rights reserved.
1. Introduction Ferrites of the spinel type MFe2O4 (M is a divalent metal cation) are magnetic materials with cubic spinel structure, which have been extensively used in various technological applications in the past decades [1,2]. Among them, CoFe2O4 (CF) are widely studied in electronic devices [3], ferrofluids [4], magnetic drug delivery [5], and microwave devices [6] due to its excellent magnetic properties [7]. However, the large density restricts its widely application [8]. Aiming to reduce density, it may be one of the effective way to synthesize CoFe2O4 on light substrate particles [9], in order to obtain core-shell particles [10]. Core-shell particles have been synthesized by a number of methods, including microemulsion [11], sol–gel techniques [12], hydrothermal synthesis [13], solvothermal [14], coprecipitation [15] and electrochemical synthesis [16]. Among these methods, coprecipitation is an easy and versatile technique [17]. However, the conventional coprecipitation method usually uses a strong base as precipitant [18], which makes it difficult to control the supersaturation properly and consequently leads to form discontinuous shell and plenty of free particles impurities without core-shell structure. This shortcoming may be overcome by the homogeneous coprecipitation method in which the precipitants such as urea release OH−gradually at elevated temperature [19]. Thus, a better control of the supersaturation could be achieved and the impurities could be suppressed greatly [20]. CoFe2O4 has been synthesized by the coprecipitation method using either Fe3+ or Fe2+ as reactant , respectively [7,21]. However, the
⁎ Corresponding author. Tel./fax: +86 10 82317103. E-mail address: [email protected] (J. Liu). 0167-577X/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2010.10.070
employment of Fe3+ usually requires the subsequent calcination (400–600 °C) [22]. while CoFe2O4 could form directly by using Fe2+ as reactant in the aqueous solution under 100 °C without further calcination process [23]. The oxidation rate of Fe2+ to Fe3+ is essential for the cobalt ferrite formation [24]. Hollow glass microspheres (HGMs) were usually used as “core” due to its low density. Hollow glass microspheres–CoFe2O4 (HGMsCF) core-shell particles were synthesized [25], but a further calcination process up to 600 °C was required. In our previous works, light multi-functional core-shell particles have been synthesized based on HGMs [26,27]. In this study, the light HGMs-CF coreshell particles were obtained with minimized impurities by the homogeneous coprecipitation method at 90 °C without calcination. 2. Materials and methods 2.1. Materials All the reagents were of analytical grade and used as received without further purification. Cobalt chloride [CoCl2·6H2O], ferrous chloride [FeCl2·4H2O], urea ((NH2)2CO), and hydrochloric acid (HCl) were purchased from Beijing Chemical Corporation (China). 2.2. Sample preparation The HGMs-CF core-shell particles were produced by homogenous coprecipitation in which urea was selected as the precipitant. First, 0.12 mol urea and 72 μl HCl were dissolved in 100 ml deionized water with magnetic stirring at room temperature, after that N2 was passing through the above solution to remove the O2 for 30 min; second, stoichiometric ferrous chloride (4 mmol) and cobalt chloride (2 mmol)
930
J. Liu et al. / Materials Letters 65 (2011) 929–932
were added under magnetic stirring and reaction solution was obtained. Then, 0.1 g HGMs were dispersed into the reaction solution. The resulting suspension was refluxed at 90 °C in a silicon oil bath for 1 hour. After that, 10 ml KNO3 (0.4 mol/L) was added dropwise and followed by refluxing at 90 °C for another 1 hour with stirring. All the steps of the reaction mentioned above were carried out under N2 atmosphere. The resulting precipitates were washed with deionized water and then filtered. The washing and filtration were repeated several times until the discard water was free of chlorides, which was checked by an AgNO3 solution. The washed powders dried at 80 °C for 12 h. Finally, the HGMs-CF core-shell particles were obtained. 2.3. Characterization The surface morphology and chemical composition of the samples were observed by using scanning electron microscope (SEM, Apollo300, CamScan) and energy dispersion X-ray (EDX, INCA PentaFETx3,
Oxford), respectively. The structure was analyzed by X-ray diffractometer (XRD, D/max 2200PC, RigaKu) with Cu Ka radiation. A vibratingsample magnetometer (VSM, BHV-50HTI, Riken Denshi) was used to study the magnetic properties of the samples. 3. Results and discussion Fig. 1 presents the SEM micrographs of the samples at different magnifications. As shown in Fig. 1a, the diameter of the HGMs is in the range of 10–80 μm. It is found that the surface of the HGMs is smooth. After the coprecipitation reaction, it is obvious that a coating is grown on the surface of the HGMs and the core-shell structure is obtained. The coating is encapsulated completely and uniformly. Furthermore, nearly no free particle impurities of none core-shell structure appears in the sample, which is attributed to the homogeneous coprecipitation method in which OH− is released gradually, and consequently the heterogeneous nucleation and growth are occurred during the
Fig. 1. SEM micrographs of samples. (a), (b) and (c), HGMs; (d), (e) and (f), HGMs-CF core-shell particles.
J. Liu et al. / Materials Letters 65 (2011) 929–932
931
Fig. 2. EDX of the CF coating of the HGMs-CF core-shell particles.
reaction [28]. The reactions are shown in Eqs. (1) and (2). Compared with Pang's method [25], our synthetic strategy needs no further calcination process and the CoFe2O4 coating could form directly in the aqueous solution. Fig. 4. Magnetization hysteresis of as-synthesized HGMs-CF core-shell particles sample. þ
−
COðNH2 Þ2 + H2 O→NH4 + CO2 + OH 2+
Co
2+
+ 2Fe
+ 6OH
−
+ 1 = 2O2 →CoFe2 O4 + 3H2 O
ð1Þ ð2Þ
Fig. 2 shows the EDX analysis of the CF coating of the HGMs-CF core-shell particles. It appears that Fe and Co exist in the coating, which suggests that both Fe and Co are coprecipitated on the surface of the HGMs. Furthermore, the Fe/Co atom ratio of the sample is 2.2, which is approximately consistent with the stoichiometric ratio of the cobalt ferrite. The elements of Ca, Na and Si are attributed to the HGMs itself. The X-ray diffraction pattern of the samples are shown in Fig. 3. Curve (a) is mainly composed of broaden peaks around 10–25° of 2θ, which suggests the amorphous structure of the HGMs. In Curve (b), peaks appeared at 2 theta = 30.1°, 35.2°, 37.1°, 43.0°, 53.4°, 56.9° and 62.6° ascribing to CoFe2O4 (220), (311), (222), (400), (422), (511) and (440) (JCPDS No.22-1086), indicating the formation of CoFe2O4. Besides, the broaden diffraction peaks of HGMs also exist in the range of 10–25˚in curve (b). Based on the result of the SEM, EDX and XRD, we draw the conclusion that the HGMs-CF core-shell particles with smooth, compact and continuous CoFe2O4 coatings are obtained by homogeneous coprecipitation at 90 °C without calcination. Magnetization measurement of the sample is carried out with a field scan of ±1.0 kOe at room temperature and the hysteresis loop of
the sample is shown in Fig. 4. This curve is typical for a soft-magnetic material. The saturation magnetization Ms and coercivity are determined to be 46 emu/g and 612 Oe, respectively. The saturation magnetization Ms is lower than the theory value (72 emu/g) of CoFe2O4 [29], which may be attributed to none-magnetic HGMs. The inset in Fig. 4 is a photo of HGMs-CF core-shell particles in ethanol with and without an external magnetic field. It is clear that the HGMsCF core-shell particles are all floating under no external magnetic field condition, which implies the greatly reduced density compared to that of theoretical bulk of CoFe2O4 (5.20 g/cm3) [8]. On the other hand, it can also be found that the HGMs-CF core-shell particles exhibit an obvious magnetic response when the external magnetic field is added, reflecting the good magnetic properties of the HGMs-CF core-shell particles visually. 4. Conclusions In summary, HGMs-CF core-shell particles have been successfully synthesized by the homogeneous coprecipitation method at 90 °C without calcination. The obtained HGMs-CF core-shell particles exhibit smooth, compact and continuous CoFe2O4 coatings on the surface of the HGMs. The saturation magnetization (Ms) and the coercivity (Hc) of as-sample were 46 emu/g and 612 Oe, respectively. The main advantage of this synthetic strategy is that the HGMs-CF core-shell particles can form directly in the aqueous solution at low temperature (90 °C) and no further calcination is needed, as well as that the free particles impurities without core-shell structure could been greatly suppressed. We suggest that this method can be applied to the scale industry production for high purity products. Acknowledgement The authors gratefully acknowledge the financial support for this work from National Natural Science Foundation of China (51001007). References
Fig. 3. XRD patterns of the HGMs (a), and HGMs-CF core-shell particles (b).
[1] Jeong U, Teng XW, Wang Y, Yang H, Xia YN. Adv Mater 2007;19:33–60. [2] Park J, Joo J, Kwon SG, Jang Y, Hyeon T. Angew Chem Int Ed 2007;46:4630–60. [3] Zhou ZP, Zhang Y, Wang ZY, Wei W, Tang WF, Shi J, et al. Appl Surf Sci 2008;254: 6972–5. [4] Morais PC, Santos RL, Pimenta ACM, Azevedo RB, Lima ECD. Thin Solid Films 2006;515:266–70. [5] Kim DH, Nikles DE, Johnson DT, Brazel CS. J Magn Magn Mater 2008;320:2390–6. [6] Allaeys JF, Mage JC. Ieee Mtt S Int Microw Symp Dig 2007;1-6:702–5. [7] Maaz K, Mumtaz A, Hasanain SK, Ceylan A. J Magn Magn Mater 2007;308:289–95. [8] Cannas C, Ardu A, Musinu A, Peddis D, Piccaluga G. Chem Mater 2008;20:6364–71.
932
J. Liu et al. / Materials Letters 65 (2011) 929–932
[9] Li YX, Yin DP, Wang ZQ, Li B, Xue G. Colloids Surf Physicochemical Eng Aspects 2009;339:100–5. [10] Wang CC, Chen IH, Lin CR, Chen CY. Advanced manufacture. Focusing New Emerg Technol 2008;594:150–4. [11] Yang YH, Jing LH, Yu XL, Yan DD, Gao MY. Chem Mater 2007;19:4123–8. [12] Liu M, Li X, Imrane H, Chen YJ, Goodrich T, Cai ZH, et al. Appl Phys Lett 2007:90. [13] Plank NOV, Snaith HJ, Ducati C, Bendall JS, Schmidt-Mende L, Welland ME. Nanotechnology 2008:19. [14] Deng D, Lee JY. Chem Mater 2008;20:1841–6. [15] Gole A, Stone JW, Gemmill WR, zur Loye HC, Murphy CJ. Langmuir 2008;24: 6232–7. [16] Hu XG, Dong SJ. J Mater Chem 2008;1279-95:1279–95. [17] Cozzoli PD, Pellegrino T, Manna L. Chem Soc Rev 2006;35:1195–208. [18] Zhao DL, Zhang HL, Zeng XW, Xia QS, Tang JT. Biomed Mater 2006;1:198–201.
[19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29]
Jia G, Yang M, Song YH, You HP, Zhang HJ. Cryst Growth Des 2009;9:301–7. Jia G, You HP, Liu K, Zheng YH, Guo N, Zhang HJ. Langmuir 2010;26:5122–8. Shaheen WM. Mater Chem Phys 2007;101:182–90. Chia CHSZ, Yusoff M, Goh SC, Haw CY, Sh. Ahmadi NMH, Lim HN. Ceram Int 2010;36:605–9. Wang J, Deng T, Dai YJ. J Alloy Comp 2006;419:155–61. Morgan BE, Lahav O, Loewenthal RE. Environ Sci Technol 2005;39:7678–83. Pang XF, Wu YF, Yang HB, Zhu HY, Xu J, Li X, Zou GT. Mater Res Bull 2009;44: 360–3. Liu JH, Wei J, Li SM. Mater Lett 2007;61:1529–32. Wei J, Liu JH, Li SM. J Magn Magn Mater 2007;312:414–7. Matijevic E. Langmuir 1994;10:8–16. Ayyappan S, Mahadevan S, Chandramohan P, Srinivasan MP, Philip J, Raj B. J Phys Chem C 2010;114:6334–41.