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Magnetic birefringence of iron oxyhydroxide nanoparticles stabilised by sucrose
Journal of Magnetism and Magnetic Materials 323 (2011) 1140–1144
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Magnetic birefringence of iron oxyhydroxide nanoparticles stabilised by sucrose M. Koralewski n, M. Pochylski, J. Gierszewski ´ , Poland Optics Laboratory, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan
a r t i c l e i n f o
a b s t r a c t
Article history: Received 21 July 2010 Received in revised form 5 November 2010 Available online 30 December 2010
Magnetically induced optical birefringence is used to investigate pharmaceutically important iron– sucrose aqueous suspensions. XRD and TEM measurements of the system of oxyhydroxide particles stabilised by sucrose have shown that this system contains iron oxyhydroxide in the form of 2–5 nm particles. The mineral form of the iron-core is suggested to be akaganeite. Anisotropy of the optical polarizability and magnetic susceptibility of akaganeite nanoparticles are calculated. The permanent dipole moment obtained for the nanoparticles studied was found to be negligible, in agreement with the characteristic superparamagnetic behaviour of the magnetic nanoparticles observed at room temperature. The Neel temperature of these nanoparticles is estimated as below 276 K. The results obtained are discussed against a background of the earlier studies of similar nanoscale systems. & 2010 Elsevier B.V. All rights reserved.
Keywords: Magnetic birefringence Cotton–Mouton effect Akaganeite nanoparticle Iron–sucrose Optical polarisability anisotropy Magnetic susceptibility anisotropy
1. Introduction Behaviour of magnetic particles dispersed in liquid has attracted much attention chiefly because of the potential application of such systems in various fields. For example, it is known that certain classes of such materials are capable of changing their flow properties from liquid-like to solid-like under the effect of an external magnetic field. This interesting feature has found applications in commercial devices such as clutches, shock absorbers and other magneto-mechanical coupling devices [1,2]. To achieve effective performance the ‘‘smart-fluids’’ of this type (magneto-rheological fluids) must be made of micrometre-size magnetic particles and this requirement has been a source of many problems. On the other hand, dispersions of nanoscale particles (ferro-fluids) do not show as profound changes in their viscosity as MR liquids. However, bimodal solutions of micrometre/nanometres particles have been found to exhibit significant increase in magneto-mechanical response in comparison to classic MR liquids [3,4]. In most of the above applications, the particles are ferro- or ferri-magnetic. Besides purely technical applications of magnetic nanoparticles, they are highly valuable from the bio-medical viewpoint. A great advantage of these substances is that they can be easily visualised using the MRI technique [5,6]. They can also be guided or held in place by means of a magnetic field and when carrying a drug can be effective for target drug delivery applications [7]. The nature of the magnetic
n
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0304-8853/$ - see front matter & 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2010.12.024
interactions allows magnetic nanoparticles also to be heated in a magnetic field to trigger drug release or to produce hyperthermia/ ablation of tissue. This last feature makes them particularly suitable in targeting and extraction of tumour cells in cancer therapy [8,9]. In contrast to the earlier mentioned magneto-mechanical applications, most of those in medical therapy require the particles to be made of superparamagnetic materials. In this paper we are focusing on yet another class of magnetic nanoparticle suspensions being particularly important in pharmaceutical applications. The polysaccharides iron complexes (PICs) are aqueous colloidal suspensions composed of iron-based core of several nanometres in diameter surrounded by a polysaccharide shell of a few nanometres in thickness [10,11]. It is well known fact that iron is essential for life and plays a very important role in all living organisms [12]. It is stored by animals and plants, as well as by bacteria, inside a protein known as ferritin [13]. Malfunction of the iron-storing mechanism of ferritin leads to serious, mostly blood diseases. In such situations an iron containing agent needs to be intravenously applied. PIC systems are pharmaceutically important substitutes for ferritin and are used for the treatment of anaemia [10,11]. Moreover, PICs are often used as model systems in physicochemical studies of ferritin. Besides the well known iron–dextran complex [10], frequently used in medical therapy [14] and in research [15], one of the commercially available PIC samples is iron–sucrose (called Venofers by American Regent Inc.), which is a complex of polynuclear iron (III)-oxyhydroxide in sucrose [16]. Although clinical applications of Venofers are well documented in literature [17], only a few works have concerned the physicochemical
M. Koralewski et al. / Journal of Magnetism and Magnetic Materials 323 (2011) 1140–1144
properties of this compound [11,18,19]. This complex was characterised by X-ray diffraction (XRD), iron-57 Mossbauer spectroscopy, transmission electron and atomic force microscopy (TEM, AFM) among other techniques [20]. Its magnetic properties were determined by magnetisation and susceptibility measurements [18]. In spite of considerable experimental effort, many of its properties are still unexplained. For instance, there is controversy concerning the iron-core mineral constitution. The X-ray diffraction data show that the structure of the iron-core is the most consistent with that of the akaganeite polymorph – b-FeOOH [11,19,21,22], whereas some authors claim that the core structure resembles rather that of 2-line ferrihidrite [18]. It is worth noting that unusually high value of magnetic moment per Fe3 + ion (16.5mB) in iron–sucrose was found by Gutierrez et al. [18], although these authors did not observe magnetisation saturation even at low temperatures. This phenomenon may probably find another explanation in the light of recent studies of ferritin in very high magnetic field (up to 55 T) [23,24]. Also in such conditions the saturation level of magnetisation has not been reached. Most of the studies of iron–sucrose PIC performed so far have been carried out on freeze-dried samples in the low temperature range, i.e. in conditions far from relevant for in vivo applications. Studies of the liquid state of PIC suspension above room temperature (RT) have been rare and mostly obscure. In this work, magnetically induced linear birefringence and its temperature dependence are presented for iron–sucrose aqueous suspension. The use of this technique allowed determination of the magnetic dipolar properties of iron oxyhydroxide nanoparticles. In addition XRD, TEM and refractive index measurements were performed. The results obtained are discussed in view of the earlier investigation of similar nanoscale systems.
2. Experimental The parenteral iron formulation used in this study was iron– sucrose (Venofers) from LEK [16,17]. Venofers was supplied as the iron–sucrose complex in 5 ml vials containing 100 mg of elemental iron in 30% sucrose aqueous solution, i.e. cFe ¼ 20 mg/ml. The iron content in the original liquid suspension was measured by inductively coupled plasma (ICP) optical emission spectrometry (OES) using VISTA-MPX (Varian) spectrometer. Within the experimental error (lower than 7%), the content of iron in the sample was as claimed by the supplier (see Table 1). For optical studies further dilution of the initial suspension was made with doubly distilled demineralised water. Room temperature X-ray diffraction measurements were performed using a D8 Advance (Bruker) diffractometer. The sample,
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i.e. original liquid suspension, was held in a glass capillary during the experiment. TEM analysis was performed with JEM-1200 EX II (JEOL) microscope operated at 80 kV. Optical linear birefringence was measured using the laboratory made set-up schematically illustrated in Fig. 1. The magnetic field (up to 2 T) was generated by profiled iron-core electromagnet. The magnetic field induction was measured by a gaussmeter (TELAtomic Inc.). The sample was held in a jacketed cylindrical glass cell whose pathlength ranged from 2 to 100 mm, depending on the iron concentration in the sample under study. The Haake programmable refrigerant circulator (Thermo-Fisher) was used for temperature measurements in the range of 276–363 K ensuring an accuracy better than 0.1 K. The light beam from He–Ne laser (Zeiss) (l ¼ 632.8 nm) was passed through a high quality Glan–Thompson polariser (P) whose transmission axis was oriented at 451 azimuth angle to the magnetic field direction. Suitably oriented quarterwave plate (l/4) transforms the elliptically polarised light into linearly polarised light with simultaneous rotation of the plane of polarisation, y. The light is then passed throughout analyser (A) on the photomultiplier detector. The change in the polarisation azimuth, i.e. the angle of rotation – y of the incident polarised light, is proportional to the sample birefringence Dn¼ n:–n?, according to the known relation:
y¼
pL l
Dn,
ð1Þ
where L denotes the length of the cell and l is the wavelength of light used. Eq. (1) shows that in order to obtain the value of birefringence, it is necessary to make an accurate measurement of the angle y. In our experimental set-up the analyser was mounted on motorised rotary stage driven by a stepper motor. The angle y was determined from the angular position of the rotary stage at which the intensity of light passing through the analyser was minimum (the so-called parabola method was used). The accuracy of the angle estimation was better than 0.0011. In order to conduct automated experiment, the current supply, gaussmeter, refrigerant circulator, analyser rotary stage and photomultiplier were all interfaced to a PC unit. A special programme wrote in LabVIEWs was used to synchronise the measurement sequence and to collect data. Birefringence measurements performed as a function of the magnetic field B allow direct calculation of the Cotton–Mouton constant CCM described by the relation:
Dn ¼ C CM lB2
ð2Þ
The dispersion and temperature dependence of light refractive index (n) of the diluted liquid suspensions of iron–sucrose were
Table 1 Selected physicochemical properties of iron–sucrose aqueous suspension studied. Error in parenthesis. Property
Value
Core Carrier Stabiliser Fe-content (mg/ml) Density (103 kg/m3)a Refractive index b
Akaganeite Water Sucrose 20 (1.4) 1.1576 (0.0001) 1.3341 (0.0001)
Core diameter (nm) XRDc TEMd
3.8 (0.7) 3 (0.5)
a
Original aqueous suspension at RT. l ¼ 632.8 nm, RT, cFe ¼ 1 g/l. c Estimated for the (2 1 1) diffraction peak. d Value in the range 2–5 nm was observed. b
Fig. 1. The experimental set-up for the magnetically induced linear optical birefringence measurements.
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Cotton–Mouton constant may be written as follows: rN Da Dw mm 2 C CM ¼ þ 30neo l mo kT kT
ð5Þ
According to Eq. (5), the values of Dw and mm can be determined from the temperature dependence of the Cotton– Mouton constant, only if the value of Da is known. Although Da could be measured in different experiments, its value can also be estimated from the saturation birefringence (observed at high magnetic fields) and the refractive index (see Eq. (3)). In other suitable cases where the magnetic field is too low to observe full birefringence saturation, an extrapolation of Dn to high-field limit yields Dns.
4. Results and discussion
Fig. 2. Refractive index dispersion of iron–sucrose aqueous suspension at room temperature for several iron concentrations. The inset shows temperature dependence of refractive index for 656.3 nm. The continuous lines are guides for the eye.
measured with a Pulfrich refractometer PR2 (Zeiss) equipped with thermostatable prism allowing measurements of n in the range of 276–318 K. Thermostat MK 70 (Zeiss) with temperature control 70.1 K was used.
3. Theoretical background Since the discovery reported by Majorana [25] and Cotton and Mouton [26], it has been known that magnetic field induces molecular ordering via dipolar alignment. Hence, the optical birefringence can be observed in suspensions of anisotropic, anisometric and diamagnetic particles. The magnetic dipoles can originate from permanent magnetic dipole moment (mm) that is inherent and characteristic of a given molecular structure or from the magnetic dipole moment induced by the magnetic field coupled with anisotropy (Dw) in the magnetic susceptibility (w) of the material under study. Analysis of steady-state birefringence of a dilute suspension of axially symmetrical particles follows the description given by Peterlin and Stuart [27], developed by O’Konski et al. [28] and discussed by other authors [29,30]. In the frames of this approach, the optical birefringence induced by a continuous magnetic field of intensity B is given by (SI units):
Dn ¼ Dns Fðb, gÞ ¼
rN Da Fðb, gÞ, 2neo
ð3Þ
where Dns is the saturation birefringence described by the anisotropy of optical polarisability Da ¼ a:–a?, rN is the volume concentration (particle number density), n is the refractive index of the solution and eo corresponds to permittivity of free space. The function F(b,g) is the statistical particle orientation function. For magnetic birefringence the parameters of the function correspond to the interaction energy of magnetic field with both permanent (mm) and induced magnetic dipole moments. In general, in the low magnetic field strength limit, after O’Konski et al. [28] the orientation function F(b,g) is given by: 2
F ¼ ðb þ 2gÞ=15,
ð4Þ 2
where b ¼ mmB/kT and g ¼ DwB /(2mokT), mo is the permeability of free space, k is the Boltzmann constant and T stands for absolute temperature. Taking into account Eqs. (2)–(4), the
The refractive index was measured for several wavelengths in the temperature range from 285 to 318 K for aqueous suspensions with medium and low concentration of iron. The results for several iron concentrations are illustrated in Fig. 2. Also the refractive index increment was calculated. Its value for l ¼656.3 nm is equal to dn/dcFe ¼2.81 ml/g. Knowledge of the dispersion of refractive index allowed us to calculate its value at 632.8 nm, i.e. at the wavelength used in magnetic birefringence measurements. The refraction index monotonically decreases with increase in temperature in a manner similar as that observed for pure water (see Fig. 2). The X-ray diffraction patterns of as-received original iron– sucrose suspension consist of broad peaks indicative of akaganeite, b-FeOOH [31] of poor crystallinity (not shown). The position of most distinguishable diffraction peak, corresponding to the (2 1 1) plane (diffraction angle 2y ¼35.31), was used with the Scherrer formula [32] to estimate the mean crystalline dimension reported in Table 1. In comparison to XRD made on freeze-dried sample [11,18,22] our diffractogram is of relatively low quality precluding from drawing decisive conclusions on the crystal structure of the system studied. However, the diffractograms recorded for the solutions with the content of iron higher than in the samples studied in this work have proved to be of quality comparable to that obtained for the classical freeze-dried samples [33]. TEM micrographs (not shown) of iron–sucrose show that the mineral core appears in the range of around 2–5 nm with average diameter of the core of approximately 3 nm. The XRD and TEM data are in very good agreement with the results obtained for iron– sucrose by Kudasheva et al. [19] and for iron–dextran by us [33] and others [11,15]. They are, however, in contradiction to the structure assignment described by Gutierrez et al. [18]. In the light of results of Nesterova et al. [34] the presence of both mineral forms of iron (akaganeite and ferrihidrite) in the system studied cannot be excluded, but this question needs more studies with attention paid to the effect of aging and the history of the sample. Magnetically induced optical birefringence was measured for several iron concentrations of iron–sucrose aqueous suspension. Selected concentration measurements were repeated for different pathlengths. Within the accuracy of the measured angle, y, the results obtained were repeatable both, on increase or decrease in the magnetic field. When the values of Dn obtained for different suspensions were normalised to iron concentration (i.e. Dn divided by the iron concentration cFe in [g/l]), a reasonable agreement between reduced magnetic birefringence was observed, which is illustrated in Fig. 3. Such results suggest that no aggregation of akaganeite particles appears or its influence is negligible, especially in the low magnetic field range. With the help of Eq. (2) and using the low magnetic field birefringence data (see dashed line in Fig. 3), the value of the Cotton–Mouton constant was calculated and normalised to the iron
M. Koralewski et al. / Journal of Magnetism and Magnetic Materials 323 (2011) 1140–1144
Fig. 3. The reduced magnetic birefringence Dn/cFe as a function of square of the applied magnetic field B2 for two iron concentration cFe ¼ 20 and 0.04 g/l of an iron–sucrose aqueous suspension. The inset shows plot of Dn/cFe vs 1/B2 to obtain high-field limiting value – Dns. The dashed line show low field region and the continuous lines are guides for the eye.
Table 2 The Cotton–Mouton constant, optical polarisability anisotropy, magnetic susceptibility anisotropy and magnetic moment of akaganeite nanoparticles with estimated error in parenthesis. Property
Value
CCM (10 14 mA 2)a Da (10 40 Cm2 V 1)b Dw (10 32 J T 2) mm (10 3mB)
203 (3) 10 (0.3) 6.8 (0.7) 2.5 (0.5)
a At RT and l ¼ 632.8 nm; for cFe ¼ 1 g/l, which is related to 3.04 1022 particles/m3. b The product Da Dw is negative; sign of Da was chosen arbitrarily.
concentration cFe in [g/l]. The specific Cotton–Mouton constant values (i.e. CCM/cFe) are listed in Table 2. The influence of polysaccharide shell can be neglected as the Cotton–Mouton constant measured for some polysaccharides is small and only slightly dependant on concentration (CCM E 0.02 10 14 mA 2) [33]. CM The value of CAk obtained for the akaganeite particles suspension examined is relatively high (see Table 2), if one compares it with the value of the Cotton–Mouton constant of organic compounds (e.g. CM nitrobenzene CNb ¼3.32 10 14 mA 2 [35]) as well as for horse spleen ferritin (estimated using literature data [36] to be equal to CM CFt E7.75 10 14 mA 2 for the same amount of iron i.e. 1 g/l). It is, however, much smaller than for aqueous suspension of goethite CM (estimated using literature data [37] as CGt E6.11 10 10 mA 2 for the same amount of iron i.e. 1 g/l). The particles of goethite, studied in [37], were much bigger (nanorods 150 25 10 nm3) than the core of the system considered. The Neel temperature, TN, for those goethite nanorods was about 350 K and the magnetic moment per particle, estimated from remnant magnetisation, was found to be about 1100mB. The value of CCM for akaganeite lower than that of goethite particles, suggests that TN for the sample studied should also be lower, even lower than RT. Moreover, it seems that such nanoscale akaganeite particles should not exhibit the net magnetic moment at room temperature. Moreover, the main CM contribution to CAk should come from the anisotropy of magnetic susceptibility Dw. We will rationalise this observation in the following paragraphs. Our results of magnetic birefringence, obtained for magnetic fields up to 2 T, are observed to be far from the saturation
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(see Fig. 3) in contrast to the situation observed for magnetite particles in different liquid carriers [38] or covered with dextran [33]. As reported by Gutierrez et al. [18], magnetisation of iron– sucrose measured in fields up to 5 T and at a few temperatures did not reach the saturation level either. We used then the approximation method for estimation of the value of Dns, which is illustrated in Fig. 3. In such an approach, the Dns value obtained for iron–sucrose normalised to 1 g/l iron concentration is equal to about 7 10 7. Making use of the density of akaganeite equal to 3.7 g/cm3 [31], its concentration could be expressed in volume fraction as f ¼4.3 10 4 ¼0.043%. Furthermore, taking into account the particle size (see Table 1), the volume concentration rN equal to 3.04 1022 m 3 is easily obtained. Putting the above value of rN and the value of refraction index (Table 1) into Eq. (3) we obtained, for the anisotropy of the optical polarizability per particle, Da ¼10 10 40 Fm2. To the best of our knowledge there are no published results of Da for akaganeite nanoparticles of such dimensions. The value obtained may be now compared with the results found for similar nanoscale systems. An estimation made using literature data [38] for magnetite particles with the core diameter of about 10 nm and in some other liquid carrier provide Damag in the range 3.7–14.7 10 37 Fm2. Our measurements of the anisotropy of the optical polarizability for aqueous suspension of magnetite particles coated with dextran having the core diameter of 15 nm, gives Damag E7 10 37 Fm2 [33]. The corresponding value for ferritin (core diameter 7 nm), for which Da was established from static light scattering experiment, was found to be equal to 5 10 37 Fm2 [36]. Although the comparison concerns different species, a decrease in Da with decreasing particle size can be noticed. Induced magnetic birefringence was measured for several temperatures and then, for each temperature, CCM was calculated for the low field regime. The results obtained for normalised CCM (i.e. CCM/cFe) are given in Fig. 4, showing the nonlinear temperature dependence of the Cotton–Mouton constant. The results can be linearised by plotting the product of TCCM vs 1/T (see Fig. 4). After linearization, the value of Dw and magnetic moment mm of the particle can be calculated from the intercept and the slope of the linear dependence, respectively, (see Table 2). It needs to be stressed that both values strongly depend on the accuracy of estimation of Da and its possible temperature dependence. In our calculations Da was treated as constant.
Fig. 4. Temperature dependence of specific Cotton–Mouton constant of iron– sucrose aqueous suspension for the iron concentration cFe ¼ 0.04 g/l. The inset shows the plot of product TCCM vs 1/T, the line is the best fit by the linear equation.
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It is well known that the magnetic properties of akaganeite particles depend on their size. It was shown by Chambaere and DeGrave [39] that TN for akaganeite particles of 130 and 380 nm varies between 252 and 298 K. Linear extrapolation of these data for low dimensions, i.e. below 10 nm, gives TN E230 K. A similar result is obtained from the extrapolation of the data for goethite studied by Bocquet et al. [40]. Both estimations are in good agreement with the recently established TN for ferritin, which should not be higher than 180 K [24]. Temperature measurements of the Cotton–Mouton constant give clear experimental evidence, corroborated by the above estimations, that for nanoparticles studied in this paper TN above 276 K cannot be expected. Examination of Table 2 shows that the net or effective magnetic moment of the akaganeite particles obtained for the temperature range studied, can be considered as negligible. Evidence of very small value of mm per particle suggest that only one per 1000 particles, or even less, will have a magnetic moment equal 3mB, i.e. approximately one statistical ion of Fe3 + (S¼5/2 configuration) will be uncompensated. Such a small number of uncompensated spins may presumably result from frustrated spins at the akaganeite core surface or can be related to the defect moments. Magnetisation measurements using vibrating sample magnetometer (VSM) were made in order to assess the possible remnant magnetisation at RT. The hysteresis loops of magnetisation recorded at 300 K for iron–sucrose suspension show nonhysteretic behaviour typical of the superparamagnetic systems, which is in agreement with the conclusion from the magneto-optical studies.
5. Conclusions In this paper we have shown the usefulness of the magnetooptical method, in combination with other experimental techniques, in estimation of the relevant magnetic and optical properties of the substance. The structural and magnetic properties of iron oxyhydroxide nanoparticles stabilised by sucrose (Venofers) have been studied by XRD, TEM and, for the first time, by the induced magnetic birefringence method. Our experimental investigation provided evidence supporting the akaganeite mineral structure of the core. The values of the anisotropy of optical polarisability and the anisotropy of magnetic susceptibility were obtained from the saturation and temperature dependence of the magnetic birefringence, respectively. Net magnetic moment per particle was found close to zero, which was consistent with the zero remnant magnetisation observed at RT, characteristic of superparamagnetic behaviour of nanoscale magnetic particles. The experiment performed furnished evidence that the Neel temperature for the studied system should be tentatively set below 276 K. As follows from the results presented, the Cotton–Mouton effect measurements can be regarded as an important tool in recognition of magnetic properties of biologically important substances as well as other types of nanoparticles.
Acknowledgements We wish to thank Dr A. Szlaferek (PAS Poznan´) for VSM measurements and Dr H. Gundelach (Schott AG) for presenting us a new prism for the refractometer. Financial support of the Ministry of Science and Higher Education, within grant no. N N202 124535 is gratefully acknowledged. References [1] W.H. Li, G.Z. Yao, G. Chen, S.H. Yeo, F.F. Yap, Smart Mater. Struct. 9 (2000) 95. [2] W. Hu, N.M. Wereley, L. Chemouni, P.C. Chen, J. Guid. Control Dyn. 30 (2007) 565. [3] M.T. Lopez-Lopez, P. Kuzhir, S. Lacis, G. Bossis, F. Gonzalez-Caballero, J.D.G. Duran, J. Phys.: Condens. Matter 18 (2006) S2803. [4] W.H. Li, X.Z. Zhang, Smart Mater. Struct. 19 (2010) 035002. [5] H.B. Na, I.C. Song, T. Hyeon, Adv. Mater. 21 (2009) 2133. [6] M. Veiseh, P. Gabikian, S.-B. Bahrami, O. Veiseh, M. Zhang, R.C. Hackman, A.C. Ravanpay, M.R. Stroud, Y. Kusuma, S.J. Hansen, D. Kwok, N.M. Munoz, R.W. Sze, W.M. Grady, N.M. Greenberg, R.G. Ellenbogen, J.M. Olson, Cancer Res. 67 (2007) 6882. [7] M. Arruebo, R. Ferna´ndez-Pacheco, M.R. Ibarra, J. Santamarı´a, Nano Today 2 (2007) 22. [8] K.E. Scarberry, E.B. Dickerson, J.F. McDonald, Z.J. Zhang, J. Am. Chem. Soc. 130 (2008) 10258. [9] V. Zablotskii, O. Lunov, C. Gomez-Polo, Acta Phys. Pol. A 115 (2009) 413. [10] E. London, J. Pharm. Sci. 93 (2004) 1838. [11] F. Funk, G.J. Long, D. Hautot, R. Buchi, J. Christl, P.G. Weidler, Hyperfine Interact 136 (2001) 73. [12] P.F. Lindley, Rep. Prog. Phys. 59 (1996) 867. [13] P.M. Harrison, P. Arosio, Biochim. Biophys. Acta 1275 (1996) 161. [14] R. Lawrence, PDA J. Pharm. Sci. Technol. 52 (1998) 190. [15] S.H. Kilcoyne, A. Gorisek, J. Magn. Magn. Mater. 177–181 (1998) 1457. [16] Venofers (iron sucrose injection) package insert, American Regent Inc. Shirley, New York, USA. [17] Venofers Medical Information Booklet, (in polish) LEK Poland, 2009. [18] L. Gutierrez, M. del Puerto Morales, F.J. Lazaro, J. Magn. Magn. Mater. 293 (2005) 69. [19] D.S. Kudasheva, J. Lai, A. Ulman, M.K. Cowman, J. Inorg. Biochem. 98 (2004) 1757 and references therein. [20] M.M. Ibrahim, G. Edwards, M.S. Seehra, B. Ganguly, G.P. Huffman, J. Appl. Phys. 75 (1994) 5873. [21] B. Knight, L.H. Bowen, R.D. Bereman, S. Huang, J. Inorg. Biochem. 73 (1999) 227. [22] S.H. Kilcoyne, J.L. Lawrence, Z. Kristallogr. 214 (1999) 666. [23] R.P. Guertin, N. Harrison, Z.X. Zhou, S. McCall, F. Drymiotis, J. Magn. Magn. Mater. 308 (2007) 97. [24] N.J.O. Silva, A. Millan, F. Palacio, E. Kampert, U. Zeitler, H. Rakoto, V.S. Amaral, Phys. Rev. B 79 (2009) 104405. [25] Q. Majorana, Compt. Rend. (Paris) 135 (1902) 159. [26] A. Cotton, H. Mouton, Ann. Chim. Phys. 11 (1907) 145, 289. [27] A. Peterlin, H.A. Stuart, Z. Phys. 112 (1939) 129. [28] C.T. O’Konski, T. Yoshioka, W.H. Orrtung, J. Phys. Chem. 63 (1952) 1558. [29] S.R. Wilson, P.J. Ridler, B.R. Jenings, J. Colloid Interface Sci. 201 (1998) 20. [30] E. Hassamony, E. Dubois, J.-C. Bacri, R. Perzynski, Yu.L. Raikher, V.I. Stepanov, Eur. Phys. J. B 5 (1989) 859. [31] R.M. Cornell, U. Schwertmann, The Iron Oxides, Wiley-VCH, Weinheim, 2003. [32] H.P. Klug, L.E. Alexander, X-ray Diffraction Procedures for Polycrystalline and Amorphous Materials, Wiley, New York, 1974. [33] M. Koralewski et al., submitted for publication. [34] M. Nesterova, J. Moreau, J.F. Banfield, Geochim. Cosmochim. Acta 67 (2003) 1177. [35] M.R. Battaglia, G.L.D. Ritchie, J. Chem. Soc. Far. Trans. 73 (1977) 209. [36] M. Pankowska, A. Dobek, J. Chem. Phys. 131 (2009) 015105. [37] B.J. Lemaire, P. Davidson, J. Ferre, J.P. Jamet, D. Petermann, P. Panine, I. Dozov, J.P. Jolivet, Eur. Phys. J. E 13 (2004) 291. [38] H.W. Davies, J.P. Llewellyn, J. Phys. D: Appl. Phys. 12 (1979) 311. [39] D.G. Chambaere, E.De Grave, Phys. Chem. Miner. 12 (1985) 176. [40] S. Bocquet, R.J. Pollard, J.D. Cashion, Phys. Rev. B 46 (1992) 11657.
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Magnetic birefringence of iron oxyhydroxide nanoparticles stabilised by sucrose M. Koralewski n, M. Pochylski, J. Gierszewski ´ , Poland Optics Laboratory, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan
a r t i c l e i n f o
a b s t r a c t
Article history: Received 21 July 2010 Received in revised form 5 November 2010 Available online 30 December 2010
Magnetically induced optical birefringence is used to investigate pharmaceutically important iron– sucrose aqueous suspensions. XRD and TEM measurements of the system of oxyhydroxide particles stabilised by sucrose have shown that this system contains iron oxyhydroxide in the form of 2–5 nm particles. The mineral form of the iron-core is suggested to be akaganeite. Anisotropy of the optical polarizability and magnetic susceptibility of akaganeite nanoparticles are calculated. The permanent dipole moment obtained for the nanoparticles studied was found to be negligible, in agreement with the characteristic superparamagnetic behaviour of the magnetic nanoparticles observed at room temperature. The Neel temperature of these nanoparticles is estimated as below 276 K. The results obtained are discussed against a background of the earlier studies of similar nanoscale systems. & 2010 Elsevier B.V. All rights reserved.
Keywords: Magnetic birefringence Cotton–Mouton effect Akaganeite nanoparticle Iron–sucrose Optical polarisability anisotropy Magnetic susceptibility anisotropy
1. Introduction Behaviour of magnetic particles dispersed in liquid has attracted much attention chiefly because of the potential application of such systems in various fields. For example, it is known that certain classes of such materials are capable of changing their flow properties from liquid-like to solid-like under the effect of an external magnetic field. This interesting feature has found applications in commercial devices such as clutches, shock absorbers and other magneto-mechanical coupling devices [1,2]. To achieve effective performance the ‘‘smart-fluids’’ of this type (magneto-rheological fluids) must be made of micrometre-size magnetic particles and this requirement has been a source of many problems. On the other hand, dispersions of nanoscale particles (ferro-fluids) do not show as profound changes in their viscosity as MR liquids. However, bimodal solutions of micrometre/nanometres particles have been found to exhibit significant increase in magneto-mechanical response in comparison to classic MR liquids [3,4]. In most of the above applications, the particles are ferro- or ferri-magnetic. Besides purely technical applications of magnetic nanoparticles, they are highly valuable from the bio-medical viewpoint. A great advantage of these substances is that they can be easily visualised using the MRI technique [5,6]. They can also be guided or held in place by means of a magnetic field and when carrying a drug can be effective for target drug delivery applications [7]. The nature of the magnetic
n
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interactions allows magnetic nanoparticles also to be heated in a magnetic field to trigger drug release or to produce hyperthermia/ ablation of tissue. This last feature makes them particularly suitable in targeting and extraction of tumour cells in cancer therapy [8,9]. In contrast to the earlier mentioned magneto-mechanical applications, most of those in medical therapy require the particles to be made of superparamagnetic materials. In this paper we are focusing on yet another class of magnetic nanoparticle suspensions being particularly important in pharmaceutical applications. The polysaccharides iron complexes (PICs) are aqueous colloidal suspensions composed of iron-based core of several nanometres in diameter surrounded by a polysaccharide shell of a few nanometres in thickness [10,11]. It is well known fact that iron is essential for life and plays a very important role in all living organisms [12]. It is stored by animals and plants, as well as by bacteria, inside a protein known as ferritin [13]. Malfunction of the iron-storing mechanism of ferritin leads to serious, mostly blood diseases. In such situations an iron containing agent needs to be intravenously applied. PIC systems are pharmaceutically important substitutes for ferritin and are used for the treatment of anaemia [10,11]. Moreover, PICs are often used as model systems in physicochemical studies of ferritin. Besides the well known iron–dextran complex [10], frequently used in medical therapy [14] and in research [15], one of the commercially available PIC samples is iron–sucrose (called Venofers by American Regent Inc.), which is a complex of polynuclear iron (III)-oxyhydroxide in sucrose [16]. Although clinical applications of Venofers are well documented in literature [17], only a few works have concerned the physicochemical
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properties of this compound [11,18,19]. This complex was characterised by X-ray diffraction (XRD), iron-57 Mossbauer spectroscopy, transmission electron and atomic force microscopy (TEM, AFM) among other techniques [20]. Its magnetic properties were determined by magnetisation and susceptibility measurements [18]. In spite of considerable experimental effort, many of its properties are still unexplained. For instance, there is controversy concerning the iron-core mineral constitution. The X-ray diffraction data show that the structure of the iron-core is the most consistent with that of the akaganeite polymorph – b-FeOOH [11,19,21,22], whereas some authors claim that the core structure resembles rather that of 2-line ferrihidrite [18]. It is worth noting that unusually high value of magnetic moment per Fe3 + ion (16.5mB) in iron–sucrose was found by Gutierrez et al. [18], although these authors did not observe magnetisation saturation even at low temperatures. This phenomenon may probably find another explanation in the light of recent studies of ferritin in very high magnetic field (up to 55 T) [23,24]. Also in such conditions the saturation level of magnetisation has not been reached. Most of the studies of iron–sucrose PIC performed so far have been carried out on freeze-dried samples in the low temperature range, i.e. in conditions far from relevant for in vivo applications. Studies of the liquid state of PIC suspension above room temperature (RT) have been rare and mostly obscure. In this work, magnetically induced linear birefringence and its temperature dependence are presented for iron–sucrose aqueous suspension. The use of this technique allowed determination of the magnetic dipolar properties of iron oxyhydroxide nanoparticles. In addition XRD, TEM and refractive index measurements were performed. The results obtained are discussed in view of the earlier investigation of similar nanoscale systems.
2. Experimental The parenteral iron formulation used in this study was iron– sucrose (Venofers) from LEK [16,17]. Venofers was supplied as the iron–sucrose complex in 5 ml vials containing 100 mg of elemental iron in 30% sucrose aqueous solution, i.e. cFe ¼ 20 mg/ml. The iron content in the original liquid suspension was measured by inductively coupled plasma (ICP) optical emission spectrometry (OES) using VISTA-MPX (Varian) spectrometer. Within the experimental error (lower than 7%), the content of iron in the sample was as claimed by the supplier (see Table 1). For optical studies further dilution of the initial suspension was made with doubly distilled demineralised water. Room temperature X-ray diffraction measurements were performed using a D8 Advance (Bruker) diffractometer. The sample,
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i.e. original liquid suspension, was held in a glass capillary during the experiment. TEM analysis was performed with JEM-1200 EX II (JEOL) microscope operated at 80 kV. Optical linear birefringence was measured using the laboratory made set-up schematically illustrated in Fig. 1. The magnetic field (up to 2 T) was generated by profiled iron-core electromagnet. The magnetic field induction was measured by a gaussmeter (TELAtomic Inc.). The sample was held in a jacketed cylindrical glass cell whose pathlength ranged from 2 to 100 mm, depending on the iron concentration in the sample under study. The Haake programmable refrigerant circulator (Thermo-Fisher) was used for temperature measurements in the range of 276–363 K ensuring an accuracy better than 0.1 K. The light beam from He–Ne laser (Zeiss) (l ¼ 632.8 nm) was passed through a high quality Glan–Thompson polariser (P) whose transmission axis was oriented at 451 azimuth angle to the magnetic field direction. Suitably oriented quarterwave plate (l/4) transforms the elliptically polarised light into linearly polarised light with simultaneous rotation of the plane of polarisation, y. The light is then passed throughout analyser (A) on the photomultiplier detector. The change in the polarisation azimuth, i.e. the angle of rotation – y of the incident polarised light, is proportional to the sample birefringence Dn¼ n:–n?, according to the known relation:
y¼
pL l
Dn,
ð1Þ
where L denotes the length of the cell and l is the wavelength of light used. Eq. (1) shows that in order to obtain the value of birefringence, it is necessary to make an accurate measurement of the angle y. In our experimental set-up the analyser was mounted on motorised rotary stage driven by a stepper motor. The angle y was determined from the angular position of the rotary stage at which the intensity of light passing through the analyser was minimum (the so-called parabola method was used). The accuracy of the angle estimation was better than 0.0011. In order to conduct automated experiment, the current supply, gaussmeter, refrigerant circulator, analyser rotary stage and photomultiplier were all interfaced to a PC unit. A special programme wrote in LabVIEWs was used to synchronise the measurement sequence and to collect data. Birefringence measurements performed as a function of the magnetic field B allow direct calculation of the Cotton–Mouton constant CCM described by the relation:
Dn ¼ C CM lB2
ð2Þ
The dispersion and temperature dependence of light refractive index (n) of the diluted liquid suspensions of iron–sucrose were
Table 1 Selected physicochemical properties of iron–sucrose aqueous suspension studied. Error in parenthesis. Property
Value
Core Carrier Stabiliser Fe-content (mg/ml) Density (103 kg/m3)a Refractive index b
Akaganeite Water Sucrose 20 (1.4) 1.1576 (0.0001) 1.3341 (0.0001)
Core diameter (nm) XRDc TEMd
3.8 (0.7) 3 (0.5)
a
Original aqueous suspension at RT. l ¼ 632.8 nm, RT, cFe ¼ 1 g/l. c Estimated for the (2 1 1) diffraction peak. d Value in the range 2–5 nm was observed. b
Fig. 1. The experimental set-up for the magnetically induced linear optical birefringence measurements.
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Cotton–Mouton constant may be written as follows: rN Da Dw mm 2 C CM ¼ þ 30neo l mo kT kT
ð5Þ
According to Eq. (5), the values of Dw and mm can be determined from the temperature dependence of the Cotton– Mouton constant, only if the value of Da is known. Although Da could be measured in different experiments, its value can also be estimated from the saturation birefringence (observed at high magnetic fields) and the refractive index (see Eq. (3)). In other suitable cases where the magnetic field is too low to observe full birefringence saturation, an extrapolation of Dn to high-field limit yields Dns.
4. Results and discussion
Fig. 2. Refractive index dispersion of iron–sucrose aqueous suspension at room temperature for several iron concentrations. The inset shows temperature dependence of refractive index for 656.3 nm. The continuous lines are guides for the eye.
measured with a Pulfrich refractometer PR2 (Zeiss) equipped with thermostatable prism allowing measurements of n in the range of 276–318 K. Thermostat MK 70 (Zeiss) with temperature control 70.1 K was used.
3. Theoretical background Since the discovery reported by Majorana [25] and Cotton and Mouton [26], it has been known that magnetic field induces molecular ordering via dipolar alignment. Hence, the optical birefringence can be observed in suspensions of anisotropic, anisometric and diamagnetic particles. The magnetic dipoles can originate from permanent magnetic dipole moment (mm) that is inherent and characteristic of a given molecular structure or from the magnetic dipole moment induced by the magnetic field coupled with anisotropy (Dw) in the magnetic susceptibility (w) of the material under study. Analysis of steady-state birefringence of a dilute suspension of axially symmetrical particles follows the description given by Peterlin and Stuart [27], developed by O’Konski et al. [28] and discussed by other authors [29,30]. In the frames of this approach, the optical birefringence induced by a continuous magnetic field of intensity B is given by (SI units):
Dn ¼ Dns Fðb, gÞ ¼
rN Da Fðb, gÞ, 2neo
ð3Þ
where Dns is the saturation birefringence described by the anisotropy of optical polarisability Da ¼ a:–a?, rN is the volume concentration (particle number density), n is the refractive index of the solution and eo corresponds to permittivity of free space. The function F(b,g) is the statistical particle orientation function. For magnetic birefringence the parameters of the function correspond to the interaction energy of magnetic field with both permanent (mm) and induced magnetic dipole moments. In general, in the low magnetic field strength limit, after O’Konski et al. [28] the orientation function F(b,g) is given by: 2
F ¼ ðb þ 2gÞ=15,
ð4Þ 2
where b ¼ mmB/kT and g ¼ DwB /(2mokT), mo is the permeability of free space, k is the Boltzmann constant and T stands for absolute temperature. Taking into account Eqs. (2)–(4), the
The refractive index was measured for several wavelengths in the temperature range from 285 to 318 K for aqueous suspensions with medium and low concentration of iron. The results for several iron concentrations are illustrated in Fig. 2. Also the refractive index increment was calculated. Its value for l ¼656.3 nm is equal to dn/dcFe ¼2.81 ml/g. Knowledge of the dispersion of refractive index allowed us to calculate its value at 632.8 nm, i.e. at the wavelength used in magnetic birefringence measurements. The refraction index monotonically decreases with increase in temperature in a manner similar as that observed for pure water (see Fig. 2). The X-ray diffraction patterns of as-received original iron– sucrose suspension consist of broad peaks indicative of akaganeite, b-FeOOH [31] of poor crystallinity (not shown). The position of most distinguishable diffraction peak, corresponding to the (2 1 1) plane (diffraction angle 2y ¼35.31), was used with the Scherrer formula [32] to estimate the mean crystalline dimension reported in Table 1. In comparison to XRD made on freeze-dried sample [11,18,22] our diffractogram is of relatively low quality precluding from drawing decisive conclusions on the crystal structure of the system studied. However, the diffractograms recorded for the solutions with the content of iron higher than in the samples studied in this work have proved to be of quality comparable to that obtained for the classical freeze-dried samples [33]. TEM micrographs (not shown) of iron–sucrose show that the mineral core appears in the range of around 2–5 nm with average diameter of the core of approximately 3 nm. The XRD and TEM data are in very good agreement with the results obtained for iron– sucrose by Kudasheva et al. [19] and for iron–dextran by us [33] and others [11,15]. They are, however, in contradiction to the structure assignment described by Gutierrez et al. [18]. In the light of results of Nesterova et al. [34] the presence of both mineral forms of iron (akaganeite and ferrihidrite) in the system studied cannot be excluded, but this question needs more studies with attention paid to the effect of aging and the history of the sample. Magnetically induced optical birefringence was measured for several iron concentrations of iron–sucrose aqueous suspension. Selected concentration measurements were repeated for different pathlengths. Within the accuracy of the measured angle, y, the results obtained were repeatable both, on increase or decrease in the magnetic field. When the values of Dn obtained for different suspensions were normalised to iron concentration (i.e. Dn divided by the iron concentration cFe in [g/l]), a reasonable agreement between reduced magnetic birefringence was observed, which is illustrated in Fig. 3. Such results suggest that no aggregation of akaganeite particles appears or its influence is negligible, especially in the low magnetic field range. With the help of Eq. (2) and using the low magnetic field birefringence data (see dashed line in Fig. 3), the value of the Cotton–Mouton constant was calculated and normalised to the iron
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Fig. 3. The reduced magnetic birefringence Dn/cFe as a function of square of the applied magnetic field B2 for two iron concentration cFe ¼ 20 and 0.04 g/l of an iron–sucrose aqueous suspension. The inset shows plot of Dn/cFe vs 1/B2 to obtain high-field limiting value – Dns. The dashed line show low field region and the continuous lines are guides for the eye.
Table 2 The Cotton–Mouton constant, optical polarisability anisotropy, magnetic susceptibility anisotropy and magnetic moment of akaganeite nanoparticles with estimated error in parenthesis. Property
Value
CCM (10 14 mA 2)a Da (10 40 Cm2 V 1)b Dw (10 32 J T 2) mm (10 3mB)
203 (3) 10 (0.3) 6.8 (0.7) 2.5 (0.5)
a At RT and l ¼ 632.8 nm; for cFe ¼ 1 g/l, which is related to 3.04 1022 particles/m3. b The product Da Dw is negative; sign of Da was chosen arbitrarily.
concentration cFe in [g/l]. The specific Cotton–Mouton constant values (i.e. CCM/cFe) are listed in Table 2. The influence of polysaccharide shell can be neglected as the Cotton–Mouton constant measured for some polysaccharides is small and only slightly dependant on concentration (CCM E 0.02 10 14 mA 2) [33]. CM The value of CAk obtained for the akaganeite particles suspension examined is relatively high (see Table 2), if one compares it with the value of the Cotton–Mouton constant of organic compounds (e.g. CM nitrobenzene CNb ¼3.32 10 14 mA 2 [35]) as well as for horse spleen ferritin (estimated using literature data [36] to be equal to CM CFt E7.75 10 14 mA 2 for the same amount of iron i.e. 1 g/l). It is, however, much smaller than for aqueous suspension of goethite CM (estimated using literature data [37] as CGt E6.11 10 10 mA 2 for the same amount of iron i.e. 1 g/l). The particles of goethite, studied in [37], were much bigger (nanorods 150 25 10 nm3) than the core of the system considered. The Neel temperature, TN, for those goethite nanorods was about 350 K and the magnetic moment per particle, estimated from remnant magnetisation, was found to be about 1100mB. The value of CCM for akaganeite lower than that of goethite particles, suggests that TN for the sample studied should also be lower, even lower than RT. Moreover, it seems that such nanoscale akaganeite particles should not exhibit the net magnetic moment at room temperature. Moreover, the main CM contribution to CAk should come from the anisotropy of magnetic susceptibility Dw. We will rationalise this observation in the following paragraphs. Our results of magnetic birefringence, obtained for magnetic fields up to 2 T, are observed to be far from the saturation
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(see Fig. 3) in contrast to the situation observed for magnetite particles in different liquid carriers [38] or covered with dextran [33]. As reported by Gutierrez et al. [18], magnetisation of iron– sucrose measured in fields up to 5 T and at a few temperatures did not reach the saturation level either. We used then the approximation method for estimation of the value of Dns, which is illustrated in Fig. 3. In such an approach, the Dns value obtained for iron–sucrose normalised to 1 g/l iron concentration is equal to about 7 10 7. Making use of the density of akaganeite equal to 3.7 g/cm3 [31], its concentration could be expressed in volume fraction as f ¼4.3 10 4 ¼0.043%. Furthermore, taking into account the particle size (see Table 1), the volume concentration rN equal to 3.04 1022 m 3 is easily obtained. Putting the above value of rN and the value of refraction index (Table 1) into Eq. (3) we obtained, for the anisotropy of the optical polarizability per particle, Da ¼10 10 40 Fm2. To the best of our knowledge there are no published results of Da for akaganeite nanoparticles of such dimensions. The value obtained may be now compared with the results found for similar nanoscale systems. An estimation made using literature data [38] for magnetite particles with the core diameter of about 10 nm and in some other liquid carrier provide Damag in the range 3.7–14.7 10 37 Fm2. Our measurements of the anisotropy of the optical polarizability for aqueous suspension of magnetite particles coated with dextran having the core diameter of 15 nm, gives Damag E7 10 37 Fm2 [33]. The corresponding value for ferritin (core diameter 7 nm), for which Da was established from static light scattering experiment, was found to be equal to 5 10 37 Fm2 [36]. Although the comparison concerns different species, a decrease in Da with decreasing particle size can be noticed. Induced magnetic birefringence was measured for several temperatures and then, for each temperature, CCM was calculated for the low field regime. The results obtained for normalised CCM (i.e. CCM/cFe) are given in Fig. 4, showing the nonlinear temperature dependence of the Cotton–Mouton constant. The results can be linearised by plotting the product of TCCM vs 1/T (see Fig. 4). After linearization, the value of Dw and magnetic moment mm of the particle can be calculated from the intercept and the slope of the linear dependence, respectively, (see Table 2). It needs to be stressed that both values strongly depend on the accuracy of estimation of Da and its possible temperature dependence. In our calculations Da was treated as constant.
Fig. 4. Temperature dependence of specific Cotton–Mouton constant of iron– sucrose aqueous suspension for the iron concentration cFe ¼ 0.04 g/l. The inset shows the plot of product TCCM vs 1/T, the line is the best fit by the linear equation.
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It is well known that the magnetic properties of akaganeite particles depend on their size. It was shown by Chambaere and DeGrave [39] that TN for akaganeite particles of 130 and 380 nm varies between 252 and 298 K. Linear extrapolation of these data for low dimensions, i.e. below 10 nm, gives TN E230 K. A similar result is obtained from the extrapolation of the data for goethite studied by Bocquet et al. [40]. Both estimations are in good agreement with the recently established TN for ferritin, which should not be higher than 180 K [24]. Temperature measurements of the Cotton–Mouton constant give clear experimental evidence, corroborated by the above estimations, that for nanoparticles studied in this paper TN above 276 K cannot be expected. Examination of Table 2 shows that the net or effective magnetic moment of the akaganeite particles obtained for the temperature range studied, can be considered as negligible. Evidence of very small value of mm per particle suggest that only one per 1000 particles, or even less, will have a magnetic moment equal 3mB, i.e. approximately one statistical ion of Fe3 + (S¼5/2 configuration) will be uncompensated. Such a small number of uncompensated spins may presumably result from frustrated spins at the akaganeite core surface or can be related to the defect moments. Magnetisation measurements using vibrating sample magnetometer (VSM) were made in order to assess the possible remnant magnetisation at RT. The hysteresis loops of magnetisation recorded at 300 K for iron–sucrose suspension show nonhysteretic behaviour typical of the superparamagnetic systems, which is in agreement with the conclusion from the magneto-optical studies.
5. Conclusions In this paper we have shown the usefulness of the magnetooptical method, in combination with other experimental techniques, in estimation of the relevant magnetic and optical properties of the substance. The structural and magnetic properties of iron oxyhydroxide nanoparticles stabilised by sucrose (Venofers) have been studied by XRD, TEM and, for the first time, by the induced magnetic birefringence method. Our experimental investigation provided evidence supporting the akaganeite mineral structure of the core. The values of the anisotropy of optical polarisability and the anisotropy of magnetic susceptibility were obtained from the saturation and temperature dependence of the magnetic birefringence, respectively. Net magnetic moment per particle was found close to zero, which was consistent with the zero remnant magnetisation observed at RT, characteristic of superparamagnetic behaviour of nanoscale magnetic particles. The experiment performed furnished evidence that the Neel temperature for the studied system should be tentatively set below 276 K. As follows from the results presented, the Cotton–Mouton effect measurements can be regarded as an important tool in recognition of magnetic properties of biologically important substances as well as other types of nanoparticles.
Acknowledgements We wish to thank Dr A. Szlaferek (PAS Poznan´) for VSM measurements and Dr H. Gundelach (Schott AG) for presenting us a new prism for the refractometer. Financial support of the Ministry of Science and Higher Education, within grant no. N N202 124535 is gratefully acknowledged. References [1] W.H. Li, G.Z. Yao, G. Chen, S.H. Yeo, F.F. Yap, Smart Mater. Struct. 9 (2000) 95. [2] W. Hu, N.M. Wereley, L. Chemouni, P.C. Chen, J. Guid. Control Dyn. 30 (2007) 565. [3] M.T. Lopez-Lopez, P. Kuzhir, S. Lacis, G. Bossis, F. Gonzalez-Caballero, J.D.G. Duran, J. Phys.: Condens. Matter 18 (2006) S2803. [4] W.H. Li, X.Z. Zhang, Smart Mater. Struct. 19 (2010) 035002. [5] H.B. Na, I.C. Song, T. Hyeon, Adv. Mater. 21 (2009) 2133. [6] M. Veiseh, P. Gabikian, S.-B. Bahrami, O. Veiseh, M. Zhang, R.C. Hackman, A.C. Ravanpay, M.R. Stroud, Y. Kusuma, S.J. Hansen, D. Kwok, N.M. Munoz, R.W. Sze, W.M. Grady, N.M. Greenberg, R.G. Ellenbogen, J.M. Olson, Cancer Res. 67 (2007) 6882. [7] M. Arruebo, R. Ferna´ndez-Pacheco, M.R. Ibarra, J. Santamarı´a, Nano Today 2 (2007) 22. [8] K.E. Scarberry, E.B. Dickerson, J.F. McDonald, Z.J. Zhang, J. Am. Chem. Soc. 130 (2008) 10258. [9] V. Zablotskii, O. Lunov, C. Gomez-Polo, Acta Phys. Pol. A 115 (2009) 413. [10] E. London, J. Pharm. Sci. 93 (2004) 1838. [11] F. Funk, G.J. Long, D. Hautot, R. Buchi, J. Christl, P.G. Weidler, Hyperfine Interact 136 (2001) 73. [12] P.F. Lindley, Rep. Prog. Phys. 59 (1996) 867. [13] P.M. Harrison, P. Arosio, Biochim. Biophys. Acta 1275 (1996) 161. [14] R. Lawrence, PDA J. Pharm. Sci. Technol. 52 (1998) 190. [15] S.H. Kilcoyne, A. Gorisek, J. Magn. Magn. Mater. 177–181 (1998) 1457. [16] Venofers (iron sucrose injection) package insert, American Regent Inc. Shirley, New York, USA. [17] Venofers Medical Information Booklet, (in polish) LEK Poland, 2009. [18] L. Gutierrez, M. del Puerto Morales, F.J. Lazaro, J. Magn. Magn. Mater. 293 (2005) 69. [19] D.S. Kudasheva, J. Lai, A. Ulman, M.K. Cowman, J. Inorg. Biochem. 98 (2004) 1757 and references therein. [20] M.M. Ibrahim, G. Edwards, M.S. Seehra, B. Ganguly, G.P. Huffman, J. Appl. Phys. 75 (1994) 5873. [21] B. Knight, L.H. Bowen, R.D. Bereman, S. Huang, J. Inorg. Biochem. 73 (1999) 227. [22] S.H. Kilcoyne, J.L. Lawrence, Z. Kristallogr. 214 (1999) 666. [23] R.P. Guertin, N. Harrison, Z.X. Zhou, S. McCall, F. Drymiotis, J. Magn. Magn. Mater. 308 (2007) 97. [24] N.J.O. Silva, A. Millan, F. Palacio, E. Kampert, U. Zeitler, H. Rakoto, V.S. Amaral, Phys. Rev. B 79 (2009) 104405. [25] Q. Majorana, Compt. Rend. (Paris) 135 (1902) 159. [26] A. Cotton, H. Mouton, Ann. Chim. Phys. 11 (1907) 145, 289. [27] A. Peterlin, H.A. Stuart, Z. Phys. 112 (1939) 129. [28] C.T. O’Konski, T. Yoshioka, W.H. Orrtung, J. Phys. Chem. 63 (1952) 1558. [29] S.R. Wilson, P.J. Ridler, B.R. Jenings, J. Colloid Interface Sci. 201 (1998) 20. [30] E. Hassamony, E. Dubois, J.-C. Bacri, R. Perzynski, Yu.L. Raikher, V.I. Stepanov, Eur. Phys. J. B 5 (1989) 859. [31] R.M. Cornell, U. Schwertmann, The Iron Oxides, Wiley-VCH, Weinheim, 2003. [32] H.P. Klug, L.E. Alexander, X-ray Diffraction Procedures for Polycrystalline and Amorphous Materials, Wiley, New York, 1974. [33] M. Koralewski et al., submitted for publication. [34] M. Nesterova, J. Moreau, J.F. Banfield, Geochim. Cosmochim. Acta 67 (2003) 1177. [35] M.R. Battaglia, G.L.D. Ritchie, J. Chem. Soc. Far. Trans. 73 (1977) 209. [36] M. Pankowska, A. Dobek, J. Chem. Phys. 131 (2009) 015105. [37] B.J. Lemaire, P. Davidson, J. Ferre, J.P. Jamet, D. Petermann, P. Panine, I. Dozov, J.P. Jolivet, Eur. Phys. J. E 13 (2004) 291. [38] H.W. Davies, J.P. Llewellyn, J. Phys. D: Appl. Phys. 12 (1979) 311. [39] D.G. Chambaere, E.De Grave, Phys. Chem. Miner. 12 (1985) 176. [40] S. Bocquet, R.J. Pollard, J.D. Cashion, Phys. Rev. B 46 (1992) 11657.