CoFe₂O₄ and CoFe₂O₄/SiO₂ Core/Shell Nanoparticles: Magnetic and Spectroscopic Study

Abstract

Spherical nanoparticles of surfactant-coated CoFe2O4 (core) were prepared through thermal \ndecomposition of metal acetylacetonates in the presence of a mixture of oleic acid and oleylamine and \nuniformly coated with silica shell by using tetraethylorthosilicate (TEOS) and ammonia in a micellar \nsolution (core/shell). Transmission electron microscopy (TEM) analysis of core/shell nanoparticles \nevidenced the high homogeneity of the coating process in producing single core/shell nanoparticles \nwith a narrow size distribution. The combined use of spectroscopic studies(NMR and FTIR) on core \nand core/shell nanoparticles pointed out that the surfactants’ layer bound to the surface core \nnanoparticles is retained also after the silica coating process. This allows to obtaining systems with \nvery similar magnetic behavior but weaker dipolar interparticle interactions and lower values of \nsaturation magnetization. In view of the interest in biomedical field, the effect of the CoFe2O4 \nnanoparticles silica coating was also studied by controlling the possible modifications in cytotoxicity \nby trypan blue and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) assays on \nhuman cells.