The recent development of biocompatible, functionalized ferrofluids and ferromagnetic particles has led to a range of new biomedical and diagnostic applications e.g. [1-4]. New studies utilizing these particles and ferrofluids in unique ways are continually appearing in the scientific literature and there are now many companies which produce these products both for research and clinical applications.
In virtually all cases, the magnetic properties of these particles play an important role in the effectiveness of the application and affect the behavior of the particles and ferrofluids in applied fields. However, very few studies have examined the magnetic properties of these particles particularly those produced by chemical synthesis techniques. As part of a study to produce gel-based ferrofluid standards for MRI analysis, we have synthesized nanoscale magnetite (Fe3O4) / maghemite (g-Fe2O3) particles in the presence of organic polymers. The resulting organic-inorganic composites form stable aqueous suspensions. We have developed methods of preparation and the detailed characterization of the structural and magnetic properties of these nanoscale magnetic particles. We show that the arrangement of the particles within clusters plays a major role in determining the observed magnetic properties .
In addition to synthesizing ferrimagnetic nanoparticles, we have been developing methods for synthesizing low-moment superparamagnetic rod-like particles with diameters of about 6nm and lengths of up to several hundred nanometres [6, 7]. These particles are analogous to ferritin in that they are precipitated on biopolymers (polysaccharides in this case). We are studying the ultrastructure of the particles with electron microscopy and neutron scattering techniques while the internal structure is probed with Mössbauer spectroscopy and x-ray absorption fine structure analysis using synchrotron radiation. One of the attractions of working with organic-inorganic nanocomposite particles is that they often have the property of self-organisation into superlattices when precipitated. One of the aims of the project is to create superlattices of single magnetic domain particles.
 U. Häfeli, W. Schütt, J. Teller, and M. Zborowski, Scientific and Clinical Applications of Magnetic Microspheres, Plenum Press, New York, 1997.
 Halbreich, J. Roger, J.N. Pons, D. Geldwerth, M.F. Da Silva, M. Roudier, and J.C. Bacri, Biochimie 80 (1998) 379.
 J. Roger, J.N. Pons, R. Massart, A. Halbreich, and J.C. Bacri, Eur. Phys. J. AP 5 (1999) 321.
 A.S. Lübbe, C. Bergemann, W. Huhnt, T. Fricke, H. Riess, J.W. Brock, and D. Huhn, Cancer Research, 56 (1996) 4694.
 Pardoe, H., Chua-anusorn, W., St. Pierre, T.G., and Dobson, J. (2001) Structural and magnetic properties of nanoscale iron oxide particles synthesized in the presence of dextran and polyvinyl alcohol. J. Magn. Magn. Mat., 225, 41-46.
 St. Pierre, T.G., Sipos, P., Chan, P., Chua-anusorn, W., Bauchspiess, K.R., Webb, J. (1994) Synthesis of nanoscale iron oxide structures using protein cages and polysaccharide networks. In: Nanophase materials (Eds: Hadjipanayis, G.C. and Siegel, R.W.) Kluwer Academic Publishers, Dordrecht pp 49-56.
 Sipos, P., St. Pierre, T.G., and Webb, J. (1995) Rod-like iron(III) oxyhydroxide particles in iron(III)-polysaccharide solutions. J. Inorg. Biochem., in press.
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