Wet chemical synthesis of zinc-iron oxide nanocomposite

Abstract

Zinc-iron oxide nanoparticles (Zn_xFe_3−xO₄ and δ-Zn_xFe_1−xOOH) were successfully synthesized by room temperature chemical reaction of a solution containing ZnCl₂ and FeCl₂ in the presence of gelatin. The composition of products could be controlled by variation of the Zn/Fe mixture ratio of the starting material. Zn_xFe_3−xO₄ nanoparticles were obtained from a solution with a high Zn/Fe ratio, whereas Zn-doped feroxyhyte (δ-Zn_xFe_1−xOOH) nanoparticles were obtained from a solution with a low Zn/Fe ratio. The Zn_xFe_3−xO₄ nanoparticles were spherical with diameters of approximately 10 nm, and the δ-Zn_xFe_1−xOOH particles were needle-like with lengths of approximately 100 nm. Mössbauer spectra measured at room temperature indicated superparamagnetic behavior of the nanoparticles, whereas the magnetic components were observed at low temperature. The Zn content of the intermediate species ($(\text {Zn}^{\text {II}}_{\mathrm {x}}\text {Fe}^{\text {II}}_{\mathrm {1-x}}\text {Fe}^{\text {III}}_{\mathrm {2}}\mathrm {O}_{4})$) plays an important role in the oxidation process. When the Zn concentration was high, the content of Fe²⁺ in the intermediate species was small, and Zn²⁺ prevented further oxidation of the nanoparticles. When the starting material had low Zn concentration, the amount of Fe²⁺ in the intermediate species became large and was rapidly oxidized into δ-Zn_xFe_1−xOOH while rinsing under the ambient atmosphere.