Novel Fe@C–TiO2 and Fe@C–SiO2 water-dispersible magnetic nanocomposites

Abstract We report the synthesis of novel nanocomposites based on Fe@C nanoparticles obtained from Fe(CO) 5 and C 2 H 4 /H 2 by laser pyrolysis technique using a three nozzles injector. The αFe–Fe x C y @C particles (below 24 nm diameter) were first functionalized with hydrophilic groups using Na carboxymethylcellulose. Oxidic precursors (Si(OC 2 H 5 ) 4 or Ti(OC 2 H 5 ) 4 ) dissolved in ethanol were mixed with ethanolic suspensions of hydrophilized Fe@C nanoparticles using strong ultrasonication, then with water (at different pH values) and finally the Fe-containing composites were recovered by magnetic separation. The SiO 2 and TiO 2 -coated powders were characterized by XRD, FT-IR and TEM techniques and their magnetic hysteresis curves were recorded at different temperatures. Both composites contain submicron aggregates of Fe@C nanoparticles embedded in/surrounded by a disordered porous oxidic matrix/shell. Near superparamagnetic behavior and room temperature and 26 A m 2 /kg (for Fe@C/SiO 2 ) or 57 A m 2 /kg (for Fe@C/TiO 2 ) saturation magnetization values were recorded and a blocking temperature around 500 K was extrapolated.