The Effect of Silica Shell Thickness on Magnetic and Proton Relaxometric Properties: Fe3O4@mSiO2 Nanoparticles

Here, we report the effect of silica shell thickness on proton relaxivities (r2 and r1) and magnetic properties. Starting from hydrophobic 7-nm of Fe3O4, we have coated Fe3O4 with cetyltrimethylammnoium bromide (CTAB) for phase transformation from hydrophobic to hydrophilic. Core-shell structure Fe3O4@mSiO2 with different silica shell thickness have been obtained. The obtained Fe3O4@mSiO2 have been characterized by TEM, FTIR, SQUID and the proton relaxivities of the nanoparticles have been determined. The presence of silica did alter the relaxivity with slightly increased the r2, and dramatically decreased the r1 of Fe3O4@mSiO2. We find that the r2 and r1 relaxivity decreased with the increase of silica shell thickness. Moreover, the high r2/r1 ratio shows that Fe3O4@mSiO2 may serve as T2 contrast agents in MRI.