Synthesis of cavity-containing iron oxide nanoparticles by hydrothermal treatment of colloidal dispersion

Nanostructured iron oxides have been widely used in catalysis, adsorption, sensor, biomedicine, and so on. In this study, iron oxide nanoparticles containing nanosized cavities were prepared by hydrothermal treatment of a colloidal dispersion of iron hydroxide. The as-prepared sample and the one calcined in air at 450 °C were composed of well-dispersed rhombohedral-like α-Fe 2 O 3 nanoparticles; calcining in nitrogen resulted in a composite of α-Fe 2 O 3 and γ-Fe 2 O 3 having superparamagnetic property. Moreover, the iron oxide nanoparticles calcined in air or nitrogen have 7–15 nm- and 5–12 nm-diameter cavities, respectively. These peculiar structures might be conducive for some applications such as adsorption involving large molecules.