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T03-P11

MжSSBAUER SPECTROSCOPY STUDY OF -Fe2O3 NANOPARTICLES MODIFIED BY HUMIC ACIDS
A. Chekanova1, T. Sorkina2, A. Dubov1, I. Perminova2, E. Goodilin1, I. Presnyakov2, Yu. Maksimov3, I. Suzdalev3.

Department of Materials Science, M.V. Lomonosov Moscow State University, 119992 Moscow, Russian Federation 2 Department of Chemistry, M.V.Lomonosov Moscow State University, 119992 Moscow, Russian Federation 3 N.N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 119992 Moscow, Russian Federation, In recent years, water-soluble magnetic nanoparticles have been actively studied because of their attractive properties for biomedical applications. They are used in drug delivery as carriers for magnetic drug targeting, in hyperthermia, protein separation, etc. For in vivo applications the magnetic particles have to be coated with a biocompatible shells to prevent aggregation during or after the synthesis process and biodegradation when exposed to the biological system. Humic acids (HA) are inexpensive natural surfactants which can be used as protective/stabilizing shells for nanoparticles [1]. In our work magnetic nanoparticles of -Fe2O3 was obtained by aerosol spray pyrolysis (ASP) method [2]. Humic acids of leonardite were used as stabilizing agents. Preparation of modified -Fe2O3 nanoparticles using HA as surfactant leads to formation of slightly associated groups of magnetite nanoparticles [3], which penetrate between branches of the HA as shown in Figure 1. The MЖssbauer spectra of the sample -Fe2O3 stabilized by the HA are given in Figure 2 and the corresponding fitted parameters are listed in Table 1. The spectra correspond to a magnetic oxide with a superparamagnetic behaviour. Indeed, lowering temperature gives "paramagnetic" signals from Fe3+ ions (a doublet and a monoline at 300 K), which turn into three sets of hyperfine structure lines (HFS). Two of which are described presence of -Fe2O3 nanoclusters of two characteristic sizes in a magnetically ordered state (16 < T < 180 K) denoted in Table 1 as -Fe2O3-1 and Fe2O3-2, respectively [2], and the third can be described as new spectral component (( = 0,43 ± 0,03 mm/s, = 0,00 ± 0,03 mm/s and in = 39,9 ± 0,5T (21%±5%)) related to an interaction of HA with the surface of hyperfine magnetic phase. Using humic acids as new non-toxic agent permits to obtain stable during long time suspensions of magnetic nanoparticles for future medical applications. Table I: MЖssbauer parameters of the -Fe2O stabilized by HA at 77K. Comp. -Fe2O3 - 1 -Fe2O3 - 2 -Fe2O3 - 3 0.41 0.42 0.43
±0.03 mm s
­1

1

Figure 1. TEM image of modified mahemite nanoparticles.
1,002

Absorption (Relative units)

1,001 1,000 0,999 0,998 0,997 0,996 0,995 0,994

-15

-10

-5

0

5

10

15

V elo sity Л Л /Я
Figure 2. MЖssbauer spectra of the -Fe2O3 stabilized by HA at 77K.

3





±0.5 T

Hin,

Relative content
(%), ±0.05%

[1] E. IllИs, E. TombАcz, Journal of Colloid and Interface Science, 295 (2006) . 115 [2] .E. Chekanova, .L. Dubov, E.A. Goodilin, et.al. Mendeleev Commun., 19 (2009) p. 4 [3] .E. Chekanova, T.A. Sorkina, .L. Dubov, et.al. Mendeleev Commun., 19 (2009) p. 72

0.00 0.00 0.00

0.78 0.78 0.78

45.4 48.7 39.9

33 46 21

111