Iron Oxide and Oxide-Hydroxide Nanoparticles in Organic-Inorganic Matrices


Article Preview

Nanometric ferrihydrite, maghemite and magnetite particles formed within an organicinorganic hybrid matrix were obtained by the sol-gel process. In contrast to precipitation techniques, sol-gel process appears as suitable way to achieve size-controlled nanoscopic magnetic particles anchored in a hybrid structure. The hybrid matrix here reported, named di-ureasil, is composed of poly(oxyethylene) chains grafted to siloxane groups by means of urea cross-linkages. The formation of ferrihydrite particles was achieved incorporating iron nitrate during the sol-gel process, at low pH. The formation of maghemite takes place after the incorporation of a mixture of Fe3+ and Fe2+ ions and treatment with an ammonia solution, after the sol-gel process. Magnetite nanoparticles are formed after the incorporation of Fe2+ ions and treatment with ammonia at 80°C. The AC magnetic susceptibility shows thermal irreversibility with a blocking temperature TB≈13K and ≈25K depending on frequency for the ferrihydrite and maghemite particles, respectively. The magnetite nanoparticles are blocked at room temperature. Above the irreversibility the magnetization of ferrihydrite and maghemite follows a Langevin function modified with a linear term, as found in antiferromagnetic and ferrimagnetic particles.



Materials Science Forum (Volumes 514-516)

Edited by:

Paula Maria Vilarinho




N. J. O. Silva et al., "Iron Oxide and Oxide-Hydroxide Nanoparticles in Organic-Inorganic Matrices", Materials Science Forum, Vols. 514-516, pp. 142-146, 2006

Online since:

May 2006




[1] F. C. Meldrum, B. R. Heywood, S. Mann, Science, 257, 522 (1992).

[2] S. Gider, D. D. Awschalom, T. Douglas, S. Mann, M. Chaparala, Science, 268, 77 (1995).

[3] T. Douglas, M. Young, Nature, 393, 152 (1998).

[4] J. A. Cowen, K. L. Tsai, J. L. Dye, J. Appl. Phys., 76, 6567 (1994).

[5] R. F. Ziolo, et al, Science, 257, 219 (1992).

[6] N. J. O. Silva et al, J. Mater. Chem., 15 484 (2005).

[7] S. Sun, C. B. Murray, D. Weller, L. Folks, A. Moser, Science, 287, 1989 (2000).

[8] N. M. Pope, R. C. Alsop, Y. -A. Chang, A. K. Sonith, J. Biomed. Mater. Res., 28, 449 (1994).

[9] L. Levy, Y. Sahoo, K. -S. Kim, E. J. Bergey, P. N. Prasad, Chem. Mater., 14, 3715 (2002).

[10] V. de Zea Bermudez, L. D. Carlos, L. Alcácer, Chem. Mater., 13, 569 (1999).

[11] A. Millan, F. Palácio, Appl. Organometalic Chem., 15, 396 (2001).

[12] L. S. Fu, R. A. Sá Ferreira, N. J. O. Silva, L. D. Carlos, V. de Zea Bermudez, J. Rocha, Chem. Mater., 16, 1507 (2005).

[13] N. J. O. Silva et al, J. Appl. Cryst., 36, 961 (2003).

[14] L. Néel, Ann. Geophys., 5, 99 (1949).

[15] S. H. Kilcoyne and R. Cywinski, J. Mag. Mag. Mater., 272-276, 1549 (2004).

[16] I. Gilbert et al , Polyhedron, 22, 2457 (2003).

[17] F. Luis et al, Phys. Rev., B 59, 11837 (1999).

Fetching data from Crossref.
This may take some time to load.