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Comparison of the Magnetic Properties for the Surface-Modified Magnetite Nanoparticles Joonsik Lee1 , Yong-Ho Choa2 , Jongryoul Kim3 , and Ki Hyeon Kim1 Department of Physics, Yeungnam University, Gyeongsan 712-749, Korea Department of Chemical Engineering, Hanyang University, Ansan 426-791, Korea Department of Metallurgical Materials Engineering, Hanyang University, Ansan 426-791, Korea The Fe3 O4 nanoparticles were synthesized by a coprecipitation method, and their particles were capsulated by 3-thiopheneacetic acid (3TA), 2, 3-meso-dimercaptosuccinic acid (DMSA) and Polyethylene glycol (PEG), respectively. The 3TA-, PEG-, and DMSA-coated Fe3 O4 nanoparticles are well dispersed in aqueous solution. The average particle sizes of the Fe3 O4 and the 3TA-, PEG-, and DMSAcoated magnetite nanoparticles were exhibited approximately 10.4, 12, 11, and 12 nm by TEM results. The mean blocking temperatures of the uncoated Fe3 O4 and the 3TA, PEG, DMSA surface-coated Fe3 O4 nanoparticles exhibited about 245 10 K, 220 10 K, 142 12 K, and 200 10 K, respectively. The values of g factor of the uncoated Fe3 O4 and the 3TA-, PEG-, and DMSA-coated Fe3 O4 nanoparticles were obtained 2.22, 2.21, 2.22, and 2.19, respectively. Index Terms—g factor, magnetite, magnetization, spin resonance, superparamagnetic.
I. INTRODUCTION
HE PHYSICAL, tribological, thermal, and mechanical properties of the superparamagnetic nanoparticles offer a high potential for several applications such as magnetic resonance imaging contrast enhancement, cell sorting or separation, tissue repair, drug delivery and hyperthermia, etc. The composition, size, morphology of the magnetic nanoparticles and their surface can be tailored by various processes to improve the magnetic properties and biocompatibility [1]–[4]. The proper surface modifications of the magnetic nanoparticles should help to disperse into suitable solvents and forming homogeneous suspended ferrofluids. Such suspensions of magnetic iron-oxide nanoparticles and their surface modification have been employed in numerous biomedical applications [5]–[8]. For these applications, the particles must have the following properties of high magnetic saturation, biocompatibility, and interactive functions at the surface. The surfaces of these particles could be modified through the creation of a few atomic layers of organic polymers or inorganic metallic or oxides, suitable for further functionalization to attach various bioactive molecules. The surface-modified iron-oxide beads are generally of core-shell type: The biological species cells, nucleic acids, and proteins are connected to the magnetite core through an organic or polymeric shell [5], [9], [10]. Many research groups have been reported the Fe O nanoparticles that were capsulated by the 3-thiopheneacetic acid (3TA), Polyethylene glycol (PEG), and 2, 3-meso-dimercaptosuccinic acid (DMSA), respectively, using various syntheses. The 3TA and DMSA introduce a dense and thin outer carboxylic acid group shell through a reaction. The surface-modified Fe O
T
Manuscript received February 21, 2011; accepted April 16, 2011. Date of current version September 23, 2011. Corresponding author: K. H. Kim (e-mail:
[email protected]). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TMAG.2011.2145414
nanoparticles by 3TA and DMSA have increased hydrophilic properties due to a large amount of -COOH groups [5]–[7] for the well dispersed in an aqueous solution. The PEG has uncharged hydrophilic residues and very high surface mobility leading to high steric exclusion [11]–[13]. Therefore, covalently immobilizing PEG on the surfaces of superparamagnetic magnetite nanoparticles is expected to effectively improve the biocompatibility of the nanoparticles. In order to compare the magnetic properties of the surface-modified Fe O nanoparticles under same synthesis method, we synthesized and characterized the Fe O nanoparticles and the surface-modified Fe O nanoparticles by the 3TA, PEG, and DMSA, respectively. II. EXPERIMENTAL PROCEDURE The Fe O nanoparticles were synthesized by the coprecipiH O and FeCl H O Fe Fe tation method. FeCl were dissolved in deionized water under nitrogen with vigorous stirring at 80 , and then the Fe O nanoparticles were obtained by adding NH OH to the solution. To obtain the 3TA-coated Fe O nanoparticles, 3TA was diluted to 0.8 mM by acetonitrile. One gram of Fe O nanoparticles was added into the 10 ml of 3TA solution with stirring for 30 min. In the H O, case of the PEG-coated Fe O nanoparticles, FeCl H O Fe Fe were dissolved in distilled FeCl under a nitrogen atmoswater with vigorous stirring at 80 phere to prevent oxidation, and then the Fe O nanoparticles were obtained by adding NH OH into the solution. To get the DMSA-coated Fe O nanoparticles, the 0.8-mol DMSA was diluted with DMSO (dimethylsulfoxide). One gram of Fe O nanoparticles was added into 10 ml of the DMSA solution with stirring in an air atmosphere for 24 h. Then, the sample was washed with ethanol five times. The morphologies, structure, composition, and size distribution of the particles were determined by using high-resolution transmission electron microscopy (Tecnai G2 F20, Philips), X-ray diffractometer, FT-IR (FTS6000, BIO-RAD), and dynamic light scattering (DLS). The magnetic properties of the particles were measured by using a Magnetic Property
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Fig. 2. X-ray diffraction patterns of (a) Fe O and (b) 3TA-coated, (c) PEGcoated, and (d) DMSA-coated Fe O nanoparticles, respectively. Fig. 1. FT-IR spectra of (a) Fe O nanoparticles and (b) PEG-coated, (c) 3TAcoated, and (d) DMSA-coated Fe O nanoparticles, respectively.
Measurement System (MPMS XL-7, Quantum Design) and Electron Paramagnetic Resonance Spectrometer (Bruker EMX 300). III. RESULTS AND DISCUSSIONS The 3TA, PEG, and DMSA polymeric capsulations of the magnetite nanoparticles were proven by FT-IR spectra in comparison to those of uncoated magnetite nanoparticles. Fig. 1 shows the FT-IR spectra of: (a) noncoated Fe O nanoparticles; (b) PEG-coated Fe O nanoparticles; (c) 3TA-coated Fe O nanoparticles; and (d) DMSA-coated Fe O nanoparticles, respectively. All the samples have characteristic absorption band of the Fe-O bond of Fe O at 572 cm [14]. In Fig. 1(b), the vibration of asymmetric carboxyl group (-COOH) was located at 1650 cm . The surface-modified Fe O with PEG attributed to the C-O-C shows a strong bond at 1107 cm ether stretch. The absorption exhibits at 1636 and 3331 cm due to stretching vibration of the C C bond and the O-H bond, respectively, as shown in Fig. 1(c). The surface-modified Fe O with DMSA shows a strong bond at 1011 cm attributed to the C-O ether stretch. The absorption exhibits at 1336 and 2988 cm due to stretching vibration of the C C bond and the S-H bond, respectively, in Fig. 1(d). The results indicate that the 3TA, PEG, and DMSA were successfully bound to the surface of Fe O nanoparticles. To analyze the crystalline structure, the X-ray diffraction patterns for the Fe O nanoparticles and the 3TA-, PEG-, and DMSA-coated Fe O nanoparticles were obtained as shown in Fig. 2. Although the 3TA, PEG, and DMSA were coated on Fe O nanoparticles, respectively, there is no difference with the Fe O crystalline structure between the Fe O and the surface-modified Fe O nanoparticles. It represents that the surface modifications did not affect the crystalline structure of the Fe O core particles, which means the Fe O nanoparticles were stable even after surface modification. In order to investigate the morphology and the size distributions, the images of nanoparticles were obtained by using TEM as shown in Fig. 3. The Fe O nanoparticles and the
Fig. 3. TEM images of (a) Fe O , and (b) 3TA-coated, (c) PEG-coated, and (d) DMSA-coated Fe O nanoparticles, respectively.
surface-modified Fe O nanoparticles are spherically well dispersed. The observed average diameters by the TEM and DLS histograms (not shown here) of size distribution for the Fe O and the 3TA-, PEG-, and DMSA-coated Fe O were 10.4, 12, 11, and 12 nm, respectively. When the size of Fe O core particles were not changed after surface modification, it can be predicted that the maximum thickness of coated 3TA, PEG, and DMSA shells on Fe O nanoparticles are about below 10 . Fig. 4 shows the magnetizations of the Fe O and the 3TA-, PEG-, and DMSA-coated Fe O , respectively. In the case of DMSA surface-coated Fe O nanoparticles, the value of saturation magnetization is nearly comparable with that of the Fe O nanoparticles. The temperature dependence of the zero-field-cooled (ZFC) and field-cooled (FC) magnetizations measured in a field of 300 Oe as shown in Fig. 5. The maximum , where in the ZFC curve defines the blocking temperatures
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IEEE TRANSACTIONS ON MAGNETICS, VOL. 47, NO. 10, OCTOBER 2011
Fig. 4. Comparison of the magnetization curves measured at 300 K for Fe O nanoparticles and the 3TA-, PEG-, and DMSA-coated Fe O nanoparticles, respectively.
Fig. 6. Comparison of (a) the magnetization curves measured from 300 K to 5 K and (b) the exponential decay of the coercivity with increasing temperature and fitted curves with the function of temperature for the Fe O nanoparticles and the 3TA-, PEG-, and DMSA-coated Fe O nanoparticles, respectively.
Fig. 5. Magnetization (M) versus temperature (T) measured in the ZFC and the FC modes at 300 Oe of the Fe O nanoparticles and the surface-modified Fe O nanoparticles by 3TA, PEG, and DMSA, respectively.
the thermal energy becomes comparable to the anisotropy energy barrier. The ZFC magnetization curves show the broad maximum at about 245 10 K, 220 10 K, 142 12 K, and 200 10 K for the Fe O nanoparticles and the 3TA, PEG, and DMSA surface-modified Fe O nanoparticles, respectively. exhibited the different values although the average sizes The of nanoparticles observed by TEM are nearly same. It would be caused by the different Fe O core size or the existence of the dead layer between core and shell. The fact of the flatness of the FC curves suggested the existence of magnetic interactions among particles [15], [16]. The measured saturation magnetization, coercivity, and the theoretical fitting results with the change of the temperature from 5 K to 300 K are shown in Fig. 6(a) and (b), respectively. The magnetizations decreased with the increase of the temperature. The thermal dependence of magnetization can be fitted by the following equation [16]: (1) where is the temperature-dependent magnetization, is the Bloch constant, and is the Bloch exponent. Fig. 6(b) shows the best fitted data by (1), The obtained and values are , Fe O , , Fe O TA , , Fe O PEG ,
and , Fe O DMSA , respectively. Bloch exponent for the surface-modified Fe O nanoparticles are less than that of the Fe O . Bloch exponent decreases with the decrease of the particle size, which is reported earlier in the case of nano-sized iron particles [17]. It implies that these behaviors are believed to be due to the presence of dead layer between the Fe O core and the surface-modified shell. The coercivities increased exponentially below and decreased to nearly zero with the increase of temperature above as expected, as shown in Fig. 6(b). For noninteracting magnetic nanoparticles, the coercivities as a function of temperature, below the block temperature follows the linear relation [18] (2) For the present nanoparticles, the variation of as a funcis found to be nonlinear, indicating the highly intion of teracting nature of the nanoparticles. The variation of the coercivity with the temperature is found to follow an exponential relation [19] (3) is the coercivity at 0 K, and is a constant. where From fitting to the logarithmic equation, and were Fe O ; 99 Oe, 0.014 obtained as 190 Oe, 0.019 (3TA-coated); 40 Oe, 0.020 (PEG-coated); and 198 Oe, (DMSA-coated), respectively, as shown in Fig. 6(b). 0.018 These observed behaviors have been explained in terms of
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ACKNOWLEDGMENT This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2010-0023003). REFERENCES
Fig. 7. EPR signals at 300 K for the uncoated Fe O nanoparticles and the 3TA-, PEG-, and DMSA-coated Fe O nanoparticles, respectively.
random dipolar interactions or exchange fluctuations among the short-range ordered magnetic clusters [20]. Based on results, theses nanoparticles exhibit the ZFC curves and random dipolar interparticle interactions or exchange fluctuations behaviors. Fig. 7 shows the electron paramagnetic resonance (EPR) lines that measured at X-band (9.79 GHz) for the Fe O and the 3TA-, PEG-, and DMSA-coated Fe O nanoparticles, respectively. At room temperature, a very broad and strong single asymmetry resonance signal is observed at a field of around 3.2 kOe. The resonance line broadening can be attributed to spin disorder possibly coming from mainly antiferromagnetic interaction between the neighboring spins in magnetic nanoparticles. These line broadenings might arise from the dipolar interaction between superparamagnetic nanoparticles [21], [22]. The difference of the resonance signals for the nanoparticles would be caused by width the magnetic loss at high frequency. The resonance magnetic exhibited at 3.20, 3.14, 3.18, and 3.20 kOe for fields the Fe O and the 3TA-, PEG-, and DMSA-coated Fe O nanoparticles, respectively, which the resonance magnetic fields are nearly comparable to those of magnetization values. The effective g values obtained the typical value of Fe O as 2.22, 2.21, 2.22, and 2.19 for the Fe O and the 3TA-, PEG-, and DMSA-coated Fe O nanoparticles, respectively. IV. CONCLUSION We have investigated the 3TA, PEG, and DMSA surfacemodification effects on Fe O nanoparticles with the average diameter of around 10 nm. The Fe O and the surface-modified Fe O nanoparticles were shown the random dipolar interparticle interactions or exchange fluctuations behaviors by ZFC , and EPR results. The average magnetic core parcurves, ticle size of the surface-modified Fe O could be a little bit smaller than those of the uncoated Fe O nanoparticles. Even after surface modification of the Fe O nanoparticles, the magnetic properties were shown the stable and very similar behaviors with those of the uncoated Fe O nanoparticles. Therefore, it can be expected that the polymeric surface-modified Fe O nanoparticles are one of the good candidate materials for biomedical applications.
[1] C. Sun, J. S. H. Lee, and M. Zhang, “Magnetic nanoparticles in MR imaging and drug delivery,” Adv. Drug Delivery Rev., vol. 60, pp. 1252–1265, 2008. [2] A. K. Gupta and M. Gupta, “Surface engineering of iron oxide nanoparticles for biomedical applications,” Biomaterials, vol. 26, pp. 3995–4021, 2005. [3] D. Caruntu, G. Caruntu, and C. J. O’Conner, “Magnetic properties of variable-sized Fe O nanoparticles synthesized from non-aqueous homogeneous solution of polyols,” J. Phys. D, vol. 40, pp. 5801–5809, 2007. [4] M. Thankur, K. De, S. Giri, S. Si, A. Kotal, and R. K. Mandal, “Interparticle interaction and size effect in polymer coated magnetite nanoparticles,” J. Phys., Condens. Matter, vol. 18, pp. 9093–9104, 2005. [5] M.-J. Kim, D.-H. Jang, and Y.-H. Choa, “Preparation and characterization of carboxyl functionalization of magnetite nanoparticles for oligonucleotide immobilization,” Phys. Scr., vol. T139, p. 014024, 2010. [6] X. Qiao, M. Bai, K. Tao, X. Gong, R. Gu, H. Watanabe, K. Sun, J. Wu, and X. Kang, “Magnetorheological behavior of polyethyene glycolcoated Fe O ferrofluids,” J. Soc. Rheology, Jpn., vol. 38, pp. 23–30, 2010. [7] Y. Liu, Z. Chen, and J. Wang, “Systematic evaluation of biocompatibility of magnetic Fe O nanoparticles with six different mammalian cell lines,” J. Nanopart. Res., vol. 13, pp. 199–212, 2011. [8] R. Hergt, W. Andra, C. G. d’Ambly, I. Hilger, W. A. Kaiser, U. Richter, and H.-G. Schmidt, “Physical limits of hyperthermia using magnetite fine particles,” IEEE Trans. Magn., vol. 34, no. 5, pp. 3745–3754, Sep. 1998. [9] C. C. Berry and A. S. G. Curtis, “Functionalization of magnetic nanoparticles for applications in biomedicine,” J Phys. D, Appl. Phys., vol. 36, pp. R198–R206, 2003. [10] M. Ma, Y. Zhang, and W. Yu, “Preparation and characterization of magnetite nanoparticles coated by amino silane,” Colloids Surf. A, Physicochem. Eng. Aspects, vol. 212, pp. 219–226, 2003. [11] M. Zhang, T. Desai, and M. Ferrari, “Proteins and cells on PEG immobilized silicon,” Biomaterials, vol. 19, pp. 953–960, 1998. [12] M. Zhang and M. Ferrari, “Reduction of protein adsorption on silicon coated with a self-assembled poly(ethylene glycol) and monomethoxypoly (ethylene glycol),” in Proc. SPIE, 1998, vol. 3528, pp. 15–19. [13] Y. Zhang, N. Kohler, and M. Zhang, “Surface modification of superparamagnetic magnetite nanoparticles and their intracellular uptake,” Biomaterials, vol. 23, pp. 1553–1561, 2002. [14] R. D. Waldron, “Infrared spectra of ferrites,” Phys. Rev., vol. 99, pp. 1727–1765, 1955. [15] C. M. Sorensen, Nanoscale Materials in Chemistry. New York: Wiley, 2002, p. 169. [16] P. V. Hendriksen and S. Linderoth, “Finite-size modifications of the magnetic properties of clusters,” Phys. Rev. B, vol. 48, pp. 7259–7273, 1993. [17] J. García-Otero, M. Porto, J. Rivas, and A. Bunde, “Influence of dipolar interaction on magnetic properties of ultrafine ferromagnetic particles,” Phys. Rev. Lett., vol. 84, pp. 167–170, 2000. [18] D. Zhang, K. J. Klabunde, and C. M. Sorensen, “Magnetization temperature dependence in iron nanoparticles,” Phys. Rev. B, vol. 58, pp. 14167–14170, 1998. [19] B. D. Cullity, Introduction to Magnetic Materials. Reading, MA: Addison-Wesley, 1972, pp. 94, 389–94, 414. [20] V. Sreeja and P. A. Joy, “Microwave-hydrothermal synyhesis of Fe O nanoparticles and their magnetic properties,” Mater. Res. Bull., vol. 42, pp. 1570–1576, 2007. [21] Y. Koseoglu, F. Yildiz, D. K. Kim, M. Muhammed, and B. Aktas, “EPR studies on Na-oleate coated Fe3O4 nanoparticles,” Phys. Stat. Sol. (c), vol. 1, pp. 3511–3515, 2004. [22] Y. Koseoglu, “Effect of surfactant coating on magnetic properties of Fe3O4 nanoparticles: ESR study,” J. Magn. Magn. Mat., vol. 300, pp. e327–e330, 2006.
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