In the present work, magnetic nanoparticles coated with silica or ORMOSIL are prepared in a two step process. In the first
step, SPIONs with 6 nm average diameter are produced by a reduction-precipitation process conducted in air and in the second one, SPIONs
were used as seeds for silica/ORMOSIL growth (below 30 nm), in situ by a modified Stöber sol-gel method. SPIONs and silica/
ORMOSIL magnetic core-shell nanostructures were characterized by X-Ray diffraction (XRD), Fourier transformed infrared (FTIR)
spectroscopy, transmission electron microscopy (TEM), Mössbauer spectroscopy and SQUID magnetometry. TEM observations of SPIONs
and silica/ORMOSIL SPIONs allow determining size and shape. FTIR allows determining silica/ORMOSIL structural fingerprints.
X-ray and Mössbauer spectroscopy allow determining the magnetite/maghemite ratio, discussed as a nanosized constrained. SPIONs and
silica/ORMOSIL SPIONs show superparamagnetic properties making them appropriated to biomedical applications.
Keywords: Superparamagnetic iron oxide nanoparticles, SPIONs, silica/ORMOSIL coating, sol-gel, core-shell nanostructures.
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