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Attachment of magnetic nanoparticles on carbon nanotubes using oleate as an interlinker molecule
Materials Chemistry and Physics 116 (2009) 438–441
Contents lists available at ScienceDirect
Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys
Attachment of magnetic nanoparticles on carbon nanotubes using oleate as an interlinker molecule Y. Liu, W. Jiang, S. Li, Z.P. Cheng, D. Song, X.J. Zhang, F.S. Li ∗ National Special Superfine Powder Engineering Research Center, Nanjing University of Science and Technology, No. 200, Xiaolingwei, Nanjing, 210094, China
a r t i c l e
i n f o
Article history: Received 20 November 2008 Received in revised form 11 March 2009 Accepted 5 April 2009 Keywords: Magnetite Carbon nanotubes Oleate Nanocomposites Solvothermal method
a b s t r a c t Novel Fe3 O4 /carbon nanotubes (CNTs) nanocomposites were prepared by a polyol-medium solvothermal method using oleate as an interlinker molecule and characterized via X-ray diffractometry, X-ray photoelectron spectroscopy, transmission electron microscopy and vibration sample magnetometry. Results indicated that the Fe3 O4 nanoparticles were successfully attached on the surface of CNTs and the nanocomposites were proved to be superparamagnetic with saturation magnetization of 50.0 emu g−1 . A proposed formation mechanism of the magnetic nanocomposites was presented. © 2009 Elsevier B.V. All rights reserved.
1. Introduction As an excellent magnetic material, the cubic spinel structured magnetite (Fe3 O4 ) nanoparticles exhibited unique physical, electric and magnetic properties based on the transfer of electrons between Fe2+ and Fe3+ in the octahedral sites [1,2]. And it is well known that, being a kind of unique one-dimensional materials, carbon nanotubes (CNTs) have attracted extensive research interests due to their unique atomic structure, high specific surface area, special chemical and electronic properties [3–6]. Significant interests have been generated in preparing multifunctional Fe3 O4 /CNTs nanocomposites for their exceptional electromagnetic properties in many applications ranging from information storage and electronic devices to medical diagnostics and drug delivery [7–9]. Recently, many strategies have been reported for the synthesis of Fe3 O4 /CNTs magnetic nanocomposites. Qu et al. [8] used chemical coprecipitation of Fe2+ and Fe3+ in the presence of CNTs in an alkaline solution to prepare Fe3 O4 /CNTs. Jiang and Gao [10] prepared the Fe3 O4 /CNTs magnetic nanocomposites by in situ solvothermal synthesis from the precursor of Fe-urea coordination complex (Fe[(NH2 )2 CO]6 (NO3 )3 ) and CNTs. Tan et al. [11] achieved the magnetic functionalization of CNTs by decoration of metal oxide nanoparticles on or in CNTs. This method involved the dispersion of CNTs in Fe(CO)5 followed by vacuum thermolysis and subsequent oxidation. However, in most of these processes, the oriented deposition of Fe3 O4 nanoparticles on
∗ Corresponding author. Tel.: +86 25 8431 5942; fax: +86 25 8431 5042. E-mail address: [email protected] (F.S. Li). 0254-0584/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.matchemphys.2009.04.009
CNTs are difficult to control and some of them detach from the CNTs. In this paper, the novelty of our consideration, compared with the previous reports, mainly bases on an interlinker molecule, a carboxylic derivative of oleate. In which, oleate molecules can essentially anchor onto the surface of CNTs and can be further linked to metal ions. Then the carboxylates would in situ reduce into Fe3 O4 on the surface of CNTs by a polyol-medium solvothermal method. It is well known that hydrothermal or solvothermal preparation is one very promising chemical controlling method, which is critical for controlling particle size, morphology, and size distribution in synthesizing and processing of the iron oxide particles [11,12]. 2. Experiment 2.1. Chemicals CNTs (diameter: 40–60 nm, purity: 95–98%) were kindly provided by Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences. The commercial CNTs were purified in the mixture of concentrated sulfuric and nitric acids (1:3 by volume) at 80 ◦ C with constant stirring for 6 h. Afterwards, the solution was diluted with distilled water and rinsed for several times until the pH value reached neutral, and then filtered and dried in vacuum at 60 ◦ C for further use. The other chemicals were analytical grade and purchased from Shanghai Chemical Company. 2.2. Preparation of Fe3 O4 /CNTs nanocomposites The Fe3 O4 /CNTs nanocomposites were synthesized as follows. In a typical procedure, 0.036 g purified CNTs, 0.6 g sodium oleate were added into a 250 mL bottom-round flask with 40 mL deionized water. After ultrasonic dispersing for 30 min, 70 mL cyclohexane was introduced with constant agitation. When the solution was heated to 75 ◦ C in a water bath, 0.1775 g of FeCl3 ·6H2 O dissolved in 30 mL ethanol was added and the system was undergoing a refluxing for 1 h. Subsequently,
Y. Liu et al. / Materials Chemistry and Physics 116 (2009) 438–441
439
etc., can be assigned to (2 2 0), (3 1 1), (4 0 0), (4 2 2), (5 1 1), (4 4 0) crystal planes of cubic Fe3 O4 , respectively. XPS spectrum provides another proof to confirm the magnetic nanocomposites. Fig. 2 is the wide scan spectrum of the sample, in which the photoelectron lines at binding energy of about 285, 530, and 711 eV are attributed to C 1s, O 1s, and Fe 2p, respectively. As shown in the inset of Fig. 2, the peaks located at 711 and 724.9 eV correspond to Fe2p3/2 and Fe2p1/2, respectively, which further confirms that the oxide in the sample was Fe3 O4 [13]. The morphology and size of the Fe3 O4 -coated CNTs were analyzed using TEM. Fig. 3a and b clearly show a sporadic decoration of CNTs with Fe3 O4 nanoparticles. It is found that Fe3 O4 nanoparticles on the surface of CNTs are approximatively spherical and about 30 nm in size. And we found that the interaction between the Fe3 O4 nanoparticles and the CNTs was quite strong because thorough ultrasonic dispersion did not remove the nanoparticles from the surface. Fig. 1. XRD patterns of purified CNTs (a) and the magnetic Fe3 O4 /CNTs nanocomposites (b).
the mixture was removed from the flask and filtered. Then the filter cake was dispersed into 40 mL ethylene glycol by sonication to form a stable solution. Meanwhile, 3.6 g sodium acetate and 1.0 g polyethylene glycol, Mw = 4000 g mol−1 , were dissolved in this solution. The suspension was transformed into a Teflon-lined stainless steel autoclave (50 mL capacity) and maintained at 200 ◦ C for 12 h, and cooled to room temperature naturally. After further rinsing, drying and grinding, the magnetic CNTs nanocomposites powders were obtained. 2.3. Characterization The magnetic Fe3 O4 /CNTs nanocomposites were characterized by X-ray diffractometer (XRD, D/max 18Kv, Bruker D8 Super Speed) with Cu K␣ radiation, X-ray photoelectron spectroscopy (XPS, Thermo, ESCALAB250), transmission electron microscopy (TEM, accelerating voltage/120 kV, Philips Tecnai 12), Fourier transform infrared (FTIR, MB154S, Bomen, Canada) and vibrating sample magnetometer (VSM, EV7, ADE, USA), respectively.
3. Results and discussion XRD patterns of purified CNTs and the magnetic Fe3 O4 /CNTs nanocomposites are illustrated in Fig. 1. In Fig. 1a, it can be seen that the diffraction peak at 2Â = 26.4◦ is the typical Bragg peak of pristine CNTs and can be estimated to be the (0 0 2) plane of CNTs. Fig. 1b is the XRD pattern of the decorated CNTs. It can be seen that the characteristic peak of CNTs still exists, and according to the JCPDS Cards No. 88-315, diffraction peaks at 30.02, 35.6, 43.32, 53.5, 57.08, 62.92,
Fig. 2. X-ray photoelectron spectrum of magnetic Fe3 O4 /CNTs nanocomposites.
Fig. 3. Representative TEM images of magnetic Fe3 O4 /CNTs nanocomposites.
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Y. Liu et al. / Materials Chemistry and Physics 116 (2009) 438–441
Fig. 4. A schematic representation of formation process of magnetic Fe3 O4 /CNTs nanocomposites.
The formation of Fe3 O4 nanoparticles on the walls of CNTs is illustrated in Fig. 4, and the proposed principle of this route is as follows: (1) When CNTs were suspended into oleate aqueous solution and subjected to ultrasonic dispersion, the CNTs could effectively absorb oleate molecules through hydrophobic interaction and thereby the hydrophilic groups of oleates will extend into solution [14,15]. (2) After addition of cyclohexane and FeCl3 ethanol solution, the ferric ions could react with the oleate attaching on the CNTs to form ferric oleate [16]. Meanwhile, the CNTs adsorbed ferric oleate could transfer from aqueous to cyclohexane phase. As shown in Fig. 5, FTIR spectra of the complex of CNTs adsorbed ferric oleate were examined. Obviously, the peaks at 1383, 2853, 2923 cm−1 are attributed to the in-plane bending vibration of methyl (–CH3 ) and the symmetric and asymmetric vibration of methylene (–CH2 –) in oleate, respectively. And the strong absorbance peaks at 1446 and 1493 cm−1 are attributed to the symmetric and asymmetric stretching vibration of –COO− . Moreover, it is noteworthy that the asymmetric stretching vibration of –COO− at 1493 cm−1 is lower than that in sodium oleate (1562 cm−1 [16]), which can be explained as the high positive charge of ferric ion and further proves the good adsorption of ferric oleate on the surface of CNTs. (3) The dissociative ferric oleate was removed via filtration and then the resulted CNTs adsorbing ferric oleate were dispersed into an ethylene glycol solution. Subsequently, the ferric oleate was in situ reduced into Fe3 O4 during following solvothermal treatment. During the reac-
Fig. 6. Magnetic hysteresis loops of Fe3 O4 /CNTs nanocomposites.
tion, these CNTs acted as templates and/or substrates for the growth of Fe3 O4 nanoparticles on their surface. Magnetic property of the obtained sample was investigated with VSM. Fig. 6 shows the magnetization hysteresis loops of Fe3 O4 /CNTs nanocomposites at room temperature. It can be seen that the saturation magnetization of Fe3 O4 /CNTs is 50.0 emu g−1 , which is lower than the value of corresponding pure bulk ferrites (Fe3 O4 , 93 emu g−1 [17]) and it may be most likely due to the smaller size of Fe3 O4 nanoparticles, their surface spins and the existence of CNTs. Moreover, there are no pronounced hysteresis loops, which can reflect a typical characteristic of superparamagnetic behavior. With this unique property, it can be used as a promising material in many fields such as cancer diagnosis and therapy. 4. Conclusions
Fig. 5. FTIR spectra of CNTs adsorbed ferric oleate.
In summary, we have demonstrated a relatively novel, reproducible polyol-medium solvothermal method of decorating the carbon nanotubes with magnetic nanoparticles, in which the oleate as an interlinker molecule played an important role. This technique verified the feasibility to synthesize magnetic Fe3 O4 /CNTs nanocomposites and could be potentially extended to other ferrite/carbon nanotubes nanocomposites by the introduction of appropriate precursors into the reaction system. VSM showed that
Y. Liu et al. / Materials Chemistry and Physics 116 (2009) 438–441
the Fe3 O4 /CNTs nanocomposites were superparamagnetic and may be used in many fields such as cancer treatment. Acknowledgments This work was supported by research grants from the National Science Foundation of China (No. 50602024), and the scientific research fund from Jiangsu province of China (No. BK2007214). References [1] S.F. Si, C.H. Li, X. Wang, D.P. Yu, Q. Peng, Y.D. Li, Cryst. Growth Des. 5 (2) (2005) 391. [2] Y.J. Cho, C.H. Kim, H.S. Kim, W.S. Lee, S.-H. Park, J. Park, Chem. Mater. 20 (2008) 4694.
[3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17]
441
S. Lijima, Nature 354 (1991) 56. D. Tasis, N. Tagmatarchis, A. Bianco, M. Prato, Chem. Rev. 106 (2006) 1105. K. Zhang, M.M.F. Yuen, J.H. Gao, B. Xu, Ann. CIRP 56 (2007) 245. G.G. Wildgoose, C.E. Banks, R.G. Compton, Small 2 (2006) 182. Z. Liu, J. Wang, D.H. Xie, G. Chen, Small 4 (2008) 462. S. Qu, J. Wang, J.L. Kong, P.Y. Yang, G. Chen, Talanta 71 (2007) 1096. F. Yang, D.L. Fu, J. Long, Q.X. Ni, Med. Hypotheses 70 (2008) 765. L.Q. Jiang, L. Gao, Chem. Mater. 15 (2003) 2848. F.Y. Tan, X.B. Fan, G.L. Zhang, F.B. Zhang, Mater. Lett. 61 (2007) 1805. Y. Li, H. Liao, Y. Qian, Mater. Res. Bull. 33 (1998) 841. T. Missana, C. Maffiotte, M. García-Gutiérrez, J. Colloid. Interf. Sci. 261 (2003) 154. M.N. Zhang, L. Su, L.Q. Mao, Carbon 44 (2006) 276. C. Richard, F. Balavoine, P. Schultz, T.W. Ebbesen, C. Mioskowski, Science 300 (2003) 775. X.T. Wen, J.X. Yang, B. He, Z.W. Gu, Curr. Appl. Phys. 8 (2008) 535. H. Iida, K. Takayanagi, T. Nakanishi, T. Osaka, J. Colloid. Interf. Sci. 314 (2007) 274.
Contents lists available at ScienceDirect
Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys
Attachment of magnetic nanoparticles on carbon nanotubes using oleate as an interlinker molecule Y. Liu, W. Jiang, S. Li, Z.P. Cheng, D. Song, X.J. Zhang, F.S. Li ∗ National Special Superfine Powder Engineering Research Center, Nanjing University of Science and Technology, No. 200, Xiaolingwei, Nanjing, 210094, China
a r t i c l e
i n f o
Article history: Received 20 November 2008 Received in revised form 11 March 2009 Accepted 5 April 2009 Keywords: Magnetite Carbon nanotubes Oleate Nanocomposites Solvothermal method
a b s t r a c t Novel Fe3 O4 /carbon nanotubes (CNTs) nanocomposites were prepared by a polyol-medium solvothermal method using oleate as an interlinker molecule and characterized via X-ray diffractometry, X-ray photoelectron spectroscopy, transmission electron microscopy and vibration sample magnetometry. Results indicated that the Fe3 O4 nanoparticles were successfully attached on the surface of CNTs and the nanocomposites were proved to be superparamagnetic with saturation magnetization of 50.0 emu g−1 . A proposed formation mechanism of the magnetic nanocomposites was presented. © 2009 Elsevier B.V. All rights reserved.
1. Introduction As an excellent magnetic material, the cubic spinel structured magnetite (Fe3 O4 ) nanoparticles exhibited unique physical, electric and magnetic properties based on the transfer of electrons between Fe2+ and Fe3+ in the octahedral sites [1,2]. And it is well known that, being a kind of unique one-dimensional materials, carbon nanotubes (CNTs) have attracted extensive research interests due to their unique atomic structure, high specific surface area, special chemical and electronic properties [3–6]. Significant interests have been generated in preparing multifunctional Fe3 O4 /CNTs nanocomposites for their exceptional electromagnetic properties in many applications ranging from information storage and electronic devices to medical diagnostics and drug delivery [7–9]. Recently, many strategies have been reported for the synthesis of Fe3 O4 /CNTs magnetic nanocomposites. Qu et al. [8] used chemical coprecipitation of Fe2+ and Fe3+ in the presence of CNTs in an alkaline solution to prepare Fe3 O4 /CNTs. Jiang and Gao [10] prepared the Fe3 O4 /CNTs magnetic nanocomposites by in situ solvothermal synthesis from the precursor of Fe-urea coordination complex (Fe[(NH2 )2 CO]6 (NO3 )3 ) and CNTs. Tan et al. [11] achieved the magnetic functionalization of CNTs by decoration of metal oxide nanoparticles on or in CNTs. This method involved the dispersion of CNTs in Fe(CO)5 followed by vacuum thermolysis and subsequent oxidation. However, in most of these processes, the oriented deposition of Fe3 O4 nanoparticles on
∗ Corresponding author. Tel.: +86 25 8431 5942; fax: +86 25 8431 5042. E-mail address: [email protected] (F.S. Li). 0254-0584/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.matchemphys.2009.04.009
CNTs are difficult to control and some of them detach from the CNTs. In this paper, the novelty of our consideration, compared with the previous reports, mainly bases on an interlinker molecule, a carboxylic derivative of oleate. In which, oleate molecules can essentially anchor onto the surface of CNTs and can be further linked to metal ions. Then the carboxylates would in situ reduce into Fe3 O4 on the surface of CNTs by a polyol-medium solvothermal method. It is well known that hydrothermal or solvothermal preparation is one very promising chemical controlling method, which is critical for controlling particle size, morphology, and size distribution in synthesizing and processing of the iron oxide particles [11,12]. 2. Experiment 2.1. Chemicals CNTs (diameter: 40–60 nm, purity: 95–98%) were kindly provided by Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences. The commercial CNTs were purified in the mixture of concentrated sulfuric and nitric acids (1:3 by volume) at 80 ◦ C with constant stirring for 6 h. Afterwards, the solution was diluted with distilled water and rinsed for several times until the pH value reached neutral, and then filtered and dried in vacuum at 60 ◦ C for further use. The other chemicals were analytical grade and purchased from Shanghai Chemical Company. 2.2. Preparation of Fe3 O4 /CNTs nanocomposites The Fe3 O4 /CNTs nanocomposites were synthesized as follows. In a typical procedure, 0.036 g purified CNTs, 0.6 g sodium oleate were added into a 250 mL bottom-round flask with 40 mL deionized water. After ultrasonic dispersing for 30 min, 70 mL cyclohexane was introduced with constant agitation. When the solution was heated to 75 ◦ C in a water bath, 0.1775 g of FeCl3 ·6H2 O dissolved in 30 mL ethanol was added and the system was undergoing a refluxing for 1 h. Subsequently,
Y. Liu et al. / Materials Chemistry and Physics 116 (2009) 438–441
439
etc., can be assigned to (2 2 0), (3 1 1), (4 0 0), (4 2 2), (5 1 1), (4 4 0) crystal planes of cubic Fe3 O4 , respectively. XPS spectrum provides another proof to confirm the magnetic nanocomposites. Fig. 2 is the wide scan spectrum of the sample, in which the photoelectron lines at binding energy of about 285, 530, and 711 eV are attributed to C 1s, O 1s, and Fe 2p, respectively. As shown in the inset of Fig. 2, the peaks located at 711 and 724.9 eV correspond to Fe2p3/2 and Fe2p1/2, respectively, which further confirms that the oxide in the sample was Fe3 O4 [13]. The morphology and size of the Fe3 O4 -coated CNTs were analyzed using TEM. Fig. 3a and b clearly show a sporadic decoration of CNTs with Fe3 O4 nanoparticles. It is found that Fe3 O4 nanoparticles on the surface of CNTs are approximatively spherical and about 30 nm in size. And we found that the interaction between the Fe3 O4 nanoparticles and the CNTs was quite strong because thorough ultrasonic dispersion did not remove the nanoparticles from the surface. Fig. 1. XRD patterns of purified CNTs (a) and the magnetic Fe3 O4 /CNTs nanocomposites (b).
the mixture was removed from the flask and filtered. Then the filter cake was dispersed into 40 mL ethylene glycol by sonication to form a stable solution. Meanwhile, 3.6 g sodium acetate and 1.0 g polyethylene glycol, Mw = 4000 g mol−1 , were dissolved in this solution. The suspension was transformed into a Teflon-lined stainless steel autoclave (50 mL capacity) and maintained at 200 ◦ C for 12 h, and cooled to room temperature naturally. After further rinsing, drying and grinding, the magnetic CNTs nanocomposites powders were obtained. 2.3. Characterization The magnetic Fe3 O4 /CNTs nanocomposites were characterized by X-ray diffractometer (XRD, D/max 18Kv, Bruker D8 Super Speed) with Cu K␣ radiation, X-ray photoelectron spectroscopy (XPS, Thermo, ESCALAB250), transmission electron microscopy (TEM, accelerating voltage/120 kV, Philips Tecnai 12), Fourier transform infrared (FTIR, MB154S, Bomen, Canada) and vibrating sample magnetometer (VSM, EV7, ADE, USA), respectively.
3. Results and discussion XRD patterns of purified CNTs and the magnetic Fe3 O4 /CNTs nanocomposites are illustrated in Fig. 1. In Fig. 1a, it can be seen that the diffraction peak at 2Â = 26.4◦ is the typical Bragg peak of pristine CNTs and can be estimated to be the (0 0 2) plane of CNTs. Fig. 1b is the XRD pattern of the decorated CNTs. It can be seen that the characteristic peak of CNTs still exists, and according to the JCPDS Cards No. 88-315, diffraction peaks at 30.02, 35.6, 43.32, 53.5, 57.08, 62.92,
Fig. 2. X-ray photoelectron spectrum of magnetic Fe3 O4 /CNTs nanocomposites.
Fig. 3. Representative TEM images of magnetic Fe3 O4 /CNTs nanocomposites.
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Y. Liu et al. / Materials Chemistry and Physics 116 (2009) 438–441
Fig. 4. A schematic representation of formation process of magnetic Fe3 O4 /CNTs nanocomposites.
The formation of Fe3 O4 nanoparticles on the walls of CNTs is illustrated in Fig. 4, and the proposed principle of this route is as follows: (1) When CNTs were suspended into oleate aqueous solution and subjected to ultrasonic dispersion, the CNTs could effectively absorb oleate molecules through hydrophobic interaction and thereby the hydrophilic groups of oleates will extend into solution [14,15]. (2) After addition of cyclohexane and FeCl3 ethanol solution, the ferric ions could react with the oleate attaching on the CNTs to form ferric oleate [16]. Meanwhile, the CNTs adsorbed ferric oleate could transfer from aqueous to cyclohexane phase. As shown in Fig. 5, FTIR spectra of the complex of CNTs adsorbed ferric oleate were examined. Obviously, the peaks at 1383, 2853, 2923 cm−1 are attributed to the in-plane bending vibration of methyl (–CH3 ) and the symmetric and asymmetric vibration of methylene (–CH2 –) in oleate, respectively. And the strong absorbance peaks at 1446 and 1493 cm−1 are attributed to the symmetric and asymmetric stretching vibration of –COO− . Moreover, it is noteworthy that the asymmetric stretching vibration of –COO− at 1493 cm−1 is lower than that in sodium oleate (1562 cm−1 [16]), which can be explained as the high positive charge of ferric ion and further proves the good adsorption of ferric oleate on the surface of CNTs. (3) The dissociative ferric oleate was removed via filtration and then the resulted CNTs adsorbing ferric oleate were dispersed into an ethylene glycol solution. Subsequently, the ferric oleate was in situ reduced into Fe3 O4 during following solvothermal treatment. During the reac-
Fig. 6. Magnetic hysteresis loops of Fe3 O4 /CNTs nanocomposites.
tion, these CNTs acted as templates and/or substrates for the growth of Fe3 O4 nanoparticles on their surface. Magnetic property of the obtained sample was investigated with VSM. Fig. 6 shows the magnetization hysteresis loops of Fe3 O4 /CNTs nanocomposites at room temperature. It can be seen that the saturation magnetization of Fe3 O4 /CNTs is 50.0 emu g−1 , which is lower than the value of corresponding pure bulk ferrites (Fe3 O4 , 93 emu g−1 [17]) and it may be most likely due to the smaller size of Fe3 O4 nanoparticles, their surface spins and the existence of CNTs. Moreover, there are no pronounced hysteresis loops, which can reflect a typical characteristic of superparamagnetic behavior. With this unique property, it can be used as a promising material in many fields such as cancer diagnosis and therapy. 4. Conclusions
Fig. 5. FTIR spectra of CNTs adsorbed ferric oleate.
In summary, we have demonstrated a relatively novel, reproducible polyol-medium solvothermal method of decorating the carbon nanotubes with magnetic nanoparticles, in which the oleate as an interlinker molecule played an important role. This technique verified the feasibility to synthesize magnetic Fe3 O4 /CNTs nanocomposites and could be potentially extended to other ferrite/carbon nanotubes nanocomposites by the introduction of appropriate precursors into the reaction system. VSM showed that
Y. Liu et al. / Materials Chemistry and Physics 116 (2009) 438–441
the Fe3 O4 /CNTs nanocomposites were superparamagnetic and may be used in many fields such as cancer treatment. Acknowledgments This work was supported by research grants from the National Science Foundation of China (No. 50602024), and the scientific research fund from Jiangsu province of China (No. BK2007214). References [1] S.F. Si, C.H. Li, X. Wang, D.P. Yu, Q. Peng, Y.D. Li, Cryst. Growth Des. 5 (2) (2005) 391. [2] Y.J. Cho, C.H. Kim, H.S. Kim, W.S. Lee, S.-H. Park, J. Park, Chem. Mater. 20 (2008) 4694.
[3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17]
441
S. Lijima, Nature 354 (1991) 56. D. Tasis, N. Tagmatarchis, A. Bianco, M. Prato, Chem. Rev. 106 (2006) 1105. K. Zhang, M.M.F. Yuen, J.H. Gao, B. Xu, Ann. CIRP 56 (2007) 245. G.G. Wildgoose, C.E. Banks, R.G. Compton, Small 2 (2006) 182. Z. Liu, J. Wang, D.H. Xie, G. Chen, Small 4 (2008) 462. S. Qu, J. Wang, J.L. Kong, P.Y. Yang, G. Chen, Talanta 71 (2007) 1096. F. Yang, D.L. Fu, J. Long, Q.X. Ni, Med. Hypotheses 70 (2008) 765. L.Q. Jiang, L. Gao, Chem. Mater. 15 (2003) 2848. F.Y. Tan, X.B. Fan, G.L. Zhang, F.B. Zhang, Mater. Lett. 61 (2007) 1805. Y. Li, H. Liao, Y. Qian, Mater. Res. Bull. 33 (1998) 841. T. Missana, C. Maffiotte, M. García-Gutiérrez, J. Colloid. Interf. Sci. 261 (2003) 154. M.N. Zhang, L. Su, L.Q. Mao, Carbon 44 (2006) 276. C. Richard, F. Balavoine, P. Schultz, T.W. Ebbesen, C. Mioskowski, Science 300 (2003) 775. X.T. Wen, J.X. Yang, B. He, Z.W. Gu, Curr. Appl. Phys. 8 (2008) 535. H. Iida, K. Takayanagi, T. Nakanishi, T. Osaka, J. Colloid. Interf. Sci. 314 (2007) 274.