γ-Fe2O3 nanoparticles prepared by combustion synthesis, followed by chemical oxidation of residual carbon with H2O2

The combustion reaction product between iron nitrate and glucose is a black powder containing nanocrystalline gamma-Fe2O3 impurified with residual carbon. After the H2O2 treatment, the carbon residue is removed, so that the carbon content decreases from 32.7% to 0.4%, and the color of the sample changes from black to reddish brown. Simultaneously the BET surface area of gamma-Fe2O3 increases dramatically from 72.6 m(2) g(-1) to 149.0 m(2) g(-1). The resulted gamma-Fe2O3 particles have a round shape and an average size of 12 nm. The average crystallite size of gamma-Fe2O3 calculated from XRD patterns was 5 nm. The resulted gamma-Fe2O3 nanoparticles exhibit a superparamagnetic behavior and a saturation magnetization of 41.5 emu g(-1). In addition to the removal of residual carbon, the H2O2 treatment also ensures the sterilization of gamma-Fe2O3 particles, which is a key requirement in the field of biomedical applications. gamma-Fe2O3 nanoparticles coated with a double layer of oleic acid were dispersed in saline solution, leading to a stable colloidal suspension. DLS measurements indicated a unimodal distribution of gamma-Fe2O3 nanoparticles and a hydrodynamic diameter of 80 nm. (C) 2014 Elsevier B.V. All rights reserved.