Skip to main content Accessibility help

Reaction Pathways at the Iron–microspherical Silica Interface: Mechanistic Aspects of the Formation of Target Iron Oxide Phases

  • Sivarajan Ramesh (a1), Israel Felner (a2), Yuri Koltypin (a1) and Aharon Gedanken (a1)


Oxidative hydrolysis of elemental iron nanoclusters on hydroxylated surfaces such as silica or alumina is known to be influenced by the degree of hydration of the surface. The understanding and control of this process is crucial in the synthesis of iron oxide coated silica microspheres with a desired magnetic property. The hydrolysis of iron nanoparticles followed by heat treatment in the case of a hydrated microspherical silica surface results in the formation of maghemite (γ–Fe2O3), whereas a dehydrated surface yielded hematite (α–Fe2O3) nanoparticles. The influence of adsorbed water on the formation of intermediate iron oxides/oxidehydroxides and the mechanistic aspects of their subsequent thermal dehydration iron oxide phases were investigated by thermogravimetric analysis, Fourier transform infrared, and Mössbauer spectroscopies. The reactions on both the hydrated and the dehydrated surfaces were found to proceed through the formation of an x-ray amorphous lepidocrocite [γ–FeO(OH)] intermediate and its subsequent dehydration to maghemite (γ–Fe2O3). Maghemite to hematite transformation was readily facilitated only on a dry silica surface. The retardation of the lepidocrocite →maghemite →hematite transformation in the case of a hydrated silica surface is suggested to arise from strong hydrogen-bonded interactions between the substrate silica and the adsorbed nanoparticles.


Corresponding author

a)Address all correspondence to this author. e-mail:


Hide All
1.Iler, R.K., The Chemistry of Silica, Solubility, Polymerization, Colloid and Surface Properties and Biochemistry (Wiley-Interscience, New York, 1979).
2.Klein, L.C., Annu. Rev. Mater. Sci. 15, 227 (1985).
3.Hench, L.L. and West, J.K., Chem. Rev. 33, 90 (1990).
4.Morrow, B.A. and McFarlan, A.J., Langmuir 7, 1695 (1991).
5.Bergna, H.E., Firment, L.E., and Swartzfager, D.G., Advances in Chemistry Series 234 (American Chemical Society, Washington, DC, 1994).
6.Chuang, I.S. and Maciel, G.E., J. Am. Chem. Soc. 118, 401 (1996).
7.Seagal, D., Chemical Synthesis of Advanced Ceramic Materials (Cambridge University Press, Cambridge, United Kingdom, 1989).
8.Stober, W., Fink, A., and Bohn, E., J. Colloid Interface Sci. 26, 62 (1968).
9.Smith, A.K., Hugues, F., Theolier, A., Basset, J.M., Ugo, R., Zadherigi, G.M., Bilhou, J.L., Bilhou-Bougnal, V., and Graydon, W.F., Inorg. Chem. 18, 3104 (1979).
10.Solymosi, F. and Pasztor, M., J. Phys. Chem. 90, 5312 (1986).
11.McNulty, G.S., Cannon, K., and Schwartz, J., Inorg. Chem. 25, 2919 (1986).
12.Basu, P., Panyotov, D., and Yates, J.T. Jr, J. Am. Chem. Soc. 110, 2074 (1988).
13.Purnell, S.K., Xu, X., Goodman, D.W., and Gates, B.C., J. Phys. Chem. 98, 4076 (1994).
14.Brenner, A., Hucul, D.A., and Hardwick, S.J., Inorg. Chem. 18, 1478 (1979).
15.Brenner, A. and Hucul, D.A., Inorg. Chem. 18, 2836 (1979).
16.Hucul, D.A. and Brenner, A., J. Phys. Chem. 85, 496 (1981).
17.Ramesh, S., Koltypin, Yu., Prozorov, R., and Gedanken, A., Chem. Mater. 9, 546 (1997).
18.Ramesh, S., Cohen, Y., Aurbach, D., and Gedanken, A., Chem. Phys. Lett. 287, 461 (1998).
19.Ramesh, S., Cohen, Y., Prozorov, R., Shafi, K.V.P.M, Aurbach, D., and Gedanken, A., J. Phys. Chem. B 102, 10234 (1998).
20.Ramesh, S., Prozorov, R., and Gedanken, A., Chem. Mater. 9, 2996 (1997).
21.Patra, A., Sominska, E., Ramesh, S., Koltypin, Yu., Zhong, Z., Minti, H., Reisfeld, R., and Gedanken, A., J. Phys. Chem. B 103, 3361 (1999).
22.Homola, A.M., Lorenz, M.R., Mastrangelo, C.J., and Tilburg, T.L., IEEE Trans. Magn. MAG–22, 716 (1986).
23.Philipse, A.P., van Bruggen, M.P.B., and Padhmamanoharan, C., Langmuir 10, 92 (1994).
24.Asuha, M.N., J. Mater. Sci. Lett. 12, 1705 (1993).
25.Chaneac, C., Tronc, E., and Jolivet, J.P., J. Mater. Chem. 6, 1905 (1996).
26.Zhang, L., Papaefthymiou, G.C., and Ying, J.Y., J. Appl. Phys. 81, 6892 (1997).
27.Liu, Y., Wang, A., and Claus, R.O., Appl. Phys. Lett. 71, 2265 (1997).
28.Niznansky, D., Rehspringer, J.L., and Drillon, M., IEEE Trans. Magn. 30, 821 (1994).
29.Ennas, G., Musinu, A., Piccaluga, G., Zedda, D., Gatteschi, D., Sangregario, C., Stanger, J.L., Concas, G., and Spano, G., Chem. Mater. 10, 495 (1998).
30.Lund, C.R.F and Dumesic, J.A., J. Phys. Chem. 85, 3175 (1981).
31.Burneau, A., Barres, O., Gallas, J.P., and Lavalley, J.C., Langmuir 6, 1364 (1990).
32.Ishikawa, T., Nitta, S., and Kondo, S., J. Chem. Soc., Faraday Trans. 1 82, 2401 (1986).
33.Ishikawa, T., Cai, W.Y., and Kandori, K., J. Chem. Soc., Faraday Trans. 88, 1173 (1992).
34.Cornell, R.M. and Schwertmann, U., The Iron Oxides: Structure, Properties, Reactions, Occurrence and Uses (VCH Verlagsgesellschaft, Weinheim, Germany, 1996).
35.Kondo, S., Muroya, M., and Fujii, K., Bull. Chem. Soc. Jpn. 47, 553 (1974).
36.Naono, H. and Nakai, K., J. Colloid Interface Sci. 128, 146 (1989).
37.Tronc, E., Jolivet, J.P., and Livage, J., Hyperfine Interact. 54, 737 (1990).
38.del Monte, F., Morales, M.P., Levy, D., Fernandez, A., Ocana, M., Roig, A., Molins, E., Grady, K.O., and Serna, C.J., Langmuir 13, 3627 (1997).


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed