High yield, facile aqueous synthesis and characterization of C18 functionalized iron oxide nanoparticles

The present study shows the synthesis of magnetite nanoparticles by co-precipitation method in three steps. The steps involve the precipitation of Fe 3 O 4 nanoparticles followed by layer by layer functionalization with silica and tetraethoxy(octadyl)silane (C18). The prepared magnetite nanoparticles were investigated by SEM, TEM, XRD, FTIR and VSM. It was suggested that the intermediate iron oxide nanoparticles were formed by the competing processes of oxidation and crystal growth after decomposition of ferrous and ferric salts. The first step synthesized nanoparticles were of around 16 ± 4 nm, second step silica coating of 18 ± 3 nm and the final step C18 were of 56 ± 6 nm. The tetraethylorthosilicate hydrolyzed to form silicic acid which further polymerizes and thereby forms a layer of silica over magnetite nanoparticles. FTIR peaks at 2854 and 2921 cm −1 confirm the layering of C18 on silica encapsulated nanoparticles which corresponds to ∼CH 2 and ∼(CH 2 ) 17 CH 3 carbon chain symmetric extension. The thickness of silica coating and C18 are 1.9 ± 0.3 nm and 38.6 ± 2.5 nm as confirmed from TEM size distribution curve. The saturation magnetism of magnetite, silica coated and C18 nanoparticles are 77.46, 74.53 and 68.76 emu g −1 respectively. Thus, Fe 3 O 4 , silica and C18 encapsulated magnetite nanoparticles were superparamagnetic.