(519e) Hermetically Coated Superparamagnetic Fe2O3 Particles with SiO2 Nanofilms

Magnetic nanoparticles are frequently coated with SiO₂ to improve their functionality and bio-compatibility in a range of biomedical and polymer nanocomposite applications. Here, a scalable flame aerosol technology is used to produce highly dispersible, superparamagnetic iron oxide nanoparticles hermetically coated with silica to retain full magnetization performance.^[1] Iron oxide particles were produced by flame spray pyrolysis (FSP) of iron acetylacetonate in xylene/acetonitrile solutions and the resulting aerosol was in-situ coated with silicon dioxide by oxidation of swirling hexamethlydisiloxane vapor.^[2] The process allows independent control of the core Fe₂O₃ (maghemite) particle properties and the thickness of their silica coating film. This ensures that the non-magnetic SiO₂ layer can be closely controlled and minimized. The optimal SiO₂ content for complete (hermetic) encapsulation of the magnetic core particles was determined by isopropanol chemisorption.^[3] The magnetization of Fe₂O₃ coated with about 2 nm thin SiO₂ layers was nearly identical to that of uncoated, pure Fe₂O₃ nanoparticles.

[1] Teleki, A., M. Suter, P. R. Kidambi, O. Ergeneman, F. Krumeich, B. J. Nelson, and S. E. Pratsinis, Hermetically-coated superparamagnetic Fe₂O₃ particles with SiO₂ nanofilms, Chem. Mat. in press, (2009).

[2] Teleki, A., M. C. Heine, F. Krumeich, M. K. Akhtar, and S. E. Pratsinis, In situ coating of flame-made TiO₂ particles with nanothin SiO₂ films, Langmuir 24, 12553 (2008).

[3] Teleki, A., M. K. Akhtar, and S. E. Pratsinis, The quality of SiO₂ coatings on flame-made TiO₂-based nanoparticles, J. Mater. Chem. 18, 3547 (2008).