Synthesis of bimetallic aluminum–iron oxide nanorice, nanocubes and nanospheres

Abstract

Bimetallic oxide nanoparticles are promising materials due to their diverse physical properties. Herein, we synthesized bimetallic aluminum oxide (AlO_x)–iron oxide (FeO_x) nanoparticles with different shapes and elemental compositions by tuning the low-temperature solvothermal reaction conditions. Bimetallic oxide nanoparticles with three different geometries (nanorice, nanocubes, and nanospheres) were obtained by varying the ratio of aluminum oleate and iron oleate precursors in 1-octanol. The concentration of iron oleate precursor in the reaction medium played an important role for the shape evolution of bimetallic oxide nanoparticles. A detailed understanding of the synthesis process and the physicochemical properties of the synthesized nanoparticles was obtained using various techniques, including high-resolution transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). XRD analysis revealed the presence of hematite (Fe₂O₃) in all nanoparticles, regardless of the shape or size. However, the Al composition of nanoparticles increased as the aluminum oleate precursor concentration was increased in the reaction medium. Furthermore, the as-synthesized bimetallic nanoparticles contained AlO_x, which was transformed into γ-Al₂O₃ and α-Al₂O₃ following high-temperature annealing, whereas the crystallinity of Fe₂O₃ was maintained.