Synthesis and controlled assembly of α-FeOOH and α-Fe2O3 nanobelt arrays on hollow glass spheres

Novel systematically patterned 1D iron oxide nanostructure arrays assembled on hollow glass spheres (HGS) are successfully prepared, and thus low density core/shell composite hollow spheres are fabricated. Glass/α-FeOOH (akaganeite) composite spheres are synthesized firstly through a facile low-temperature hydrothermal process independent of surfactants or external forces. The α-FeOOH shells are assembled by nanobelts with a mean width of ca. 100 nm and an average length of 700 nm. After calcining at 400 °C for 3.0 h, α-Fe2O3 (hematite) nanostructure arrays grown on HGS can be obtained, preserving the same belt-like morphology. On the basis of a series of contrast experiments, the probable growth process of the akaganeite nanobelts on HGS is proposed. Magnetic measurements of the glass/α-Fe2O3 core/shell products are carried out, and the results show that the as-obtained products exhibit weakly ferromagnetic behaviors at room temperature, which are much enhanced at a lower temperature (5 K).