Silica-coated Cobalt Ferrite Nanoparticles for Magnetic Hyperthermia

Silica-coated Cobalt Ferrite Nanoparticles for Magnetic Hyperthermia

Yousaf Iqbal · Hongsub Bae · Ashfaq Ahmad · Ilsu Rhee ^∗

Department of Physics, Kyungpook National University, Daegu 702-701, Korea

Sungwook Hong

Division of Science Education, Daegu University, Gyeongsan 712-714, Korea.

(Received 9 December 2014 : revised 27 January 2015 : accepted 29 January 2015)

We report the synthesis and the characterization of silica-coated cobalt ferrite nanoparticles with a core-shell structure for magnetic hyperthermia. The silica-coated cobalt ferrite nanoparticles were synthesized by using the reverse micelle method. X-Ray diffraction (XRD) confirmed the crystallinity of the cubic spinel structure. Transmission electron microscopy (TEM) results depicted a spherical core-shell structure with a uniform size distribution of nanoparticles having an average diameter of 17 nm. The binding of the silica on the surface of the cobalt ferrite nanoparticles was revealed by using measurements made with a Fourier-transform infrared spectrometer (FTIR). The saturation magnetization of our synthesized nanoparticles was 42.4 emu/g, as measured by using a vibrating sample magnetometer (VSM). Moreover, the specific absorption rate of the nanoparticles dispersed in water at a concentration of 30 mg/ml was investigated in an alternating magnetic field of 1.03 kA/m with a frequency of 260 kHz. The nanoparticles showed significant heat release, demonstrating their potential for magnetic hyperthermia.

PACS numbers: 81.05.Ni, 76.60.Es, 61.46.Df, 87.61.-c

Keywords: Cobalt ferrite, Silica coating, Magnetic hyperthermia, Specific absorption rate (SAR).

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. XRD (X-ray Diffraction)\  ¦ : Ÿ x K   ïµ 1 Ïà Ô ` … s à Ô { 9  _    & ñ ½ ¨› ¸\  ¦ › ' a ¹ 1 Ï % i  . s \  ¦ : Ÿ x K   ï µ

1 Ïà Ô ` … s à Ô { 9    H { 9 ~ ½ Ó Û ¼x 3 A q (cubic spinel)½ ¨› ¸\  ¦ f ” `  ¦ ^  ¦ à º e ” % 3  . TEM (Transmission Electron Microscope)`  ¦ : Ÿ x K 
” ¸{ 9    H f ”  â s  17 nm “   ½ ¨+ þ A_  { 9  e ” `  ¦ · ú ˜ à º e ” % 3  . z  ´o   _


” ¸{ 9   ³ ð€  \ _   ҂ à Ì © œI   H FTIR (Fourier Transform Infrared Spectrometer)`  ¦ : Ÿ x K  › ' a ¹ 1 Ï 

%

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” ¸{ 9  _   l & h  $ í | 9 “ É r VSM (Vibrating Sample Magnetometer)`  ¦ : Ÿ x K  œ í © œ $ í `  ¦ ˜ Ðe ” 

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¦ · ú ˜ à º e ” % 3 “ ¦, Ÿ í o  o• ¸  H 42.4 emu/ge ” s  › ' a ¹ 1 Ï÷ &% 3  .
” ¸{ 9   à º6   xÓ  o`  ¦  l  © œ_  [ jl  1.03 147

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License

(http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any

medium, provided the original work is properly cited.

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PACS numbers: 81.05.Ni, 76.60.Es, 61.46.Df, 87.61.-c Keywords:  ïµ 1 Ïà Ô ` … s à Ô, z  ´o    ïh A,  $ í \ P “ : r ´ òõ , SAR

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∗

E-mail: [email protected]



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Fig. 1. (Color online) (a) TEM image of the silica-coated cobalt oxide nanoparticles (b) Particle size distributions for one hundred particles obtained from a TEM image.

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Fig. 2. (Color online) XRD patterns of the silica-coated cobalt ferrite nanoparticles. The indices of the crystal plane in the figure match with those of inverse cubic spinel structure.

Fig. 3. (Color online) FTIR spectra of the silica-coated cobalt ferrite nanoparticles.

%

i  Û ¼x 3 A q ½ ¨› ¸\ " f ˜ Ðs   H t à º(indices)ü < { 9 u ô  Ç . Õ ª o

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– Ð  ïh A ) a  ïµ 1 Ïà Ô ` … s à Ô
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[18].  t } Œ •Ü ¼– Ð 610 cm ⁻¹ \  e ”   H  Œ •“ É r f  ¨ à º{   H Fe-O-

Si   ½ + Ë\  e ”   H Fe-O Û ¼à ÔY Ug A\  _ ô  Ç  כ s  . 0 Aü < ° ú  

Fig. 4. (Color online) Hysteresis curve of the silica- coated cobalt ferrite nanoparticles at room temperature.

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 spot f ”  ⠓ É r 0.5 cm s  . s   H r « Ñ\  ¦ { Œ ™“ É r : Ÿ x _  f ”  â õ  ° ú  “ ¦, s \     r « Ñ\  @ /ô  Ç ¨ î ç  H“ : r • ¸ 8 £ ¤& ñ  ) a  .

Figure 5 \  [ j r « Ñ 30, 22.5, 15 mg/ml_  y h A (heating) r

ç ß –\    É r à º6   xÓ  o_  “ : r • ¸    o\  ¦ ˜ Ð# ŒÅ ғ ¦ e ”  . [ j r 

«

Ñ — ¸¿ º 600 - 800œ í_  r ç ß –  â õ  Ê ê\   H [ jŸ í º ¡ ¤  H “ : r

•

¸“   42 ^◦ C \  • ¸² ú ˜† < Ê`  ¦ ˜ Ð# ŒÅ ғ ¦ e ”   [20].  $ í
” ¸{ 9 



\  _ K  µ 1 ÏÒ q t ) a \ P “ É r r « Ñ_  y Œ •  Òì  r _  “ : r • ¸\  ¦ Z  }“   .

s

 \ P \  _ K  r « Ñ_  „  ^ ‰& h “   “ : r • ¸   o ∆T  €  

∆Q = m _W c _W ∆T +m _Si c _Si ∆T +m _Co c _Co ∆T +m _{F e} c _{F e} ∆T (1)

Fig. 5. (Color online) Heating effect of the dispersions of the silica-coated cobalt ferrite nanoparticles.

ü

< ° ú  s  ³ ð‰ & ³ ) a  . # Œl " f c ^W , c Si , c Co , c F e   H Ó ü t, z  ´o 

,  ïµ 1 Ïà Ô, ^ o = 1 p x _  q \ P s “ ¦, m W , m _Si , m _Co , m _{F e}   H r 

«

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” ¸{ 9  _  \ P “ : r ´ òõ \  ¦
 

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SAR = ∆Q − ∆T m Co + m F e

= ∆T /∆t m Co + m F e

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∼ = m W c W

m _Co + m _{F e}

 ∆T

∆t



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REFERENCES

[1] M. R. DeGuire, G. Kalonji and R. C. OïHandley, J.

Am. Ceram. Soc. 73, 3002 (1990).

[2] M. A. Willard, Y. Nakamura, E. D. Laughlin and E.

M. McHenry, J. Am. Ceram. Soc. 82, 3342 (1999).

[3] M. Ishikawa, H. Tanaka and T. Kawai, Appl. Phys.

Lett. 86, 222504 (2005).

[4] R. Hergt and S. Dutz, J. Magn. Magn. Mater. 311, 187 (2007).

[5] I. Sharifi, H. Shokrollahi and S. Amiri, J. Magn.

Magn. Mater. 324, 903 (2012).

[6] M. Johannsen, U. Greveckow, L. Eckelt, N. Wald- ofner and R. Scholz et al., Int. J. Hyperthermia 21, 637 (2005).

[7] H. S. Huang and J. F. Hainfeld, Int. J. Nanomed.

2013:8, 2521 (2013).

[8] R. E. Rosensweig, J. Magn. Magn. Mater. 252, 370 (2002).

[9] L. Y. Zhang, H. C. Gu and X. M. Wang, J. Magn.

Magn. Mater. 311, 228 (2007).

[10] T. Ahmad, H. Bae, I. Rhee, Y. Chang and S. Jin et al., J. Nanosci. Nanotech. 12, 5132 (2012).

[11] T. Ahmad, Y. Iqbal, H. Bae, I. Rhee and S. Hong et al., J. Korean Phys. Soc. 62, 1696 (2013).

[12] H. Bae, T. Ahmad, I. Rhee, Y. Chang and S. Jin et al., Nanoscale Res. Lett. 7, 44 (2012).

[13] T. Ahmad, I. Rhee, S. Hong, Y. Chang and J. Lee, J. Korean Phys. Soc. 56, 1545 (2010).

[14] J. Lee, Y. Lee, J.-K. Youn, H.-B. Na and T. Yu et al., Small 4, 143 (2008).

[15] L. Chen, Z. Xu, H. Dai and S. Zhang, J. Alloys Compd. 497, 221 (2010).

[16] S. Bruni, F. Cariati, M. Casu, A. Lai and A. Musinu et al., Nanostruct. Mater. 11, 573 (1999).

[17] J. Lewandowska- Lan´ ncucka, M. Staszewska, M.

Szuwarzynski, M. Kepczynski and M. Romek et al., J. Alloys Compd. 586, 45 (2014).

[18] B. Moji´ c, K. P. Giannakopoulos, Z. Cveji´ c and V.

V. Srdi´ c, Ceram. Int. 38, 6635 (2012).

[19] Y. D. Yin and A. P. Alivisatos, Nature 437, 664 (2005).

[20] A. Jordan, R. Scholz, P. Wust, A. Schirra and T.

Schiestel et al., J. Magn. Magn. Mater. 194, 185 (1999).

[21] A. Cervadoro, M. Cho, J. Key, C. Cooper and C.

Stigliano et al., ACS Appl. Mater. Interfaces 6, 12939 (2014).

[22] P. Guaridia, R. D. Carato, L. Lartigue, C. Wilhelm

and A. Espinosa et al., J. Am. Chem. Soc. 6, 3080

(2012).