Fe 3 O 4 /SiO 2 Core Shell Nanostructures: Preparation and Characterization

Silica coated iron oxide nanoparticles with controlled silica shell thickness were prepared by a modified Stöber method. Modification of the Stöber method consisted of changing the synthesis conditions to control the thickness of the SiO 2 shell. The core-shell nanoparticles were characterized by means of X-ray diffraction, transmission electron microscopy, Fourier-transform infrared spectroscopy and vibrational sample magnetometry. It was found that the shell formed after 8 hours of stirring. An increase of the tetraethoxysilane- magnetite mass ratio from 12.5 to 25.1 led to an increase of the shell thickness, whereas further increase in the tetraethoxysilane-magnetite mass ratio (from 25.1 to 37.6) led to decrease shell thickness. The core size has only insignificant influence on the shell thickness. Magnetic properties of composite particles correlate well with properties of pure magnetite nanoparticles considering dilution of magnetic particles by silica. Obtained results can be used for fabrication of silica shell with controlled thickness on the surface of different sized magnetite nanoparticles.