Hydrothermal synthesis of monodisperse magnetic nanoparticles. Toward bio-catalyst carrier of various sizes
Résumé
The synthesis of magnetic nanoparticles with a controlled size has always been of scientific and technological interest. Indeed, the reduction of the particle size leads to new and original magnetic properties as superparamagnetism.(Jeong et al. 2007) Nowdays, magnetic nanoparticles have attracted much attention due to their usefulness as colloidal mediators for cancer hyperthermia, contrast agent for magnetic resonance imaging (MRI) and bio-catalyst carrier.(Moret et al. 2004, Gao et al. 2003). Indeed, enzyme activity can benefit much from the use of small solid carriers. (Gao et al. 2003) We report here the synthesis of maghemite nanoparticles with an average grain size located in the range 20 – 50 nm and stable in acidic conditions. They were obtained by the Massart method co-precipitation of selected ratios of Fe(II) and Fe(III) with TAMOH in water, followed by an hydrothermal treatment at 200°C for various times. The nanoparticules were fully characterized by different techniques, including TEM, magnetization curves and Mössbauer measurements. The silica encapsulation of such particles, either by using the Stöber method or the microemulsion process involving tetraethyl orthosilicate (TEOS) and/or 3-aminopropyltriethyloxysilane (APTS), will be described.(Wang et al. 2006) Indeed, silica is fairly biocompatible and can be easily surface functionalized for bioconjugation and targeting for various applications in biological systems.(Lu et al. 2007) Preliminary results obtained by functionalizing the silica core shell with biomolecules, (e.g. antibodies) will be briefly discussed. References Jeong U., Teng, X., Wang Y., Yang H., Xia Y.: Superparamagnetic colloids: controlled synthesis and niche applications. Adv. Mater. Vol. 19, 2007, pp. 33-60. Moret S., Vasseur S., Grasset F., Duguet E.: Magnetic nanoparticles design for medical diagnosis and therapy. J. Mater. Chem. Vol 14, 2004, pp. 2161-2175. Gao X., Yu K. K. M., Tam K. Y., Tsang S. C. : Colloidal stabel silica encapsulated nano-magnetic composite as a novel bio-ctalyst carrier. Chem. Commun. 2003, pp. 2998-2999. Wang L., Wang K., Santra S., Zhao X., Hilliard L. R., Smith J. E., Wu Y., Tan W.: Watching silica nanoparticles glow in the biological world. Analytical Chem. 2006, pp. 647-654. Lu C.-W., Hung Y., Hsiao J.-K, Yao M., Chung T.-H., Lin Y.-S., Wu S.-H., Hsu S.-C., Liu H.-M., Mou C.Y., Yang C.-S., Huang D.-M., Chen Y.-C. Nano Letter Vol. 7(1), 2007, pp. 149-154.