Amino surface modification of Fe₃O₄/SiO₂ nanoparticles for bioengineering applications

The purpose of this research was to synthesise Fe₃O₄/SiO₂ nanoparticles (NPs) modified by amine groups for bioengineering applications. Magnetic iron oxide NPs were prepared via coprecipitation. The NPs were then modified with a thin layer of amorphous silica, as described by Stober. The particle surface was then terminated with amine groups. The results showed that smaller particles can be synthesised by decreasing the NaOH concentration, which, in the present case, corresponded to 35 nm using 0·9M NaOH at 750 rev min⁻¹ with a specific surface area of 41 m² g⁻¹. For uncoated Fe₃O₄ NPs, the results showed an octahedral geometry with saturation magnetisation range of 80–100 emu g⁻¹ and coercivity of 80–120 Oe for particles between 35 and 96 nm respectively. The Fe₃O₄/SiO₂ NPs with 50 nm particle size demonstrated a magnetisation value of 30 emu g⁻¹. The stable magnetic fluid contained well dispersed Fe₃O₄/SiO₂/3-aminopropyltriethoxysilane NPs, which indicated fast magnetic response.