Controlled synthesis and gas-sensing properties of hollow sea urchin-like α-Fe2O3 nanostructures and α-Fe2O3 nanocubes

Hollow sea urchin-like α-Fe2O3 nanostructures were successfully synthesized by a hydrothermal approach using FeCl3 and Na2SO4 as raw materials, and subsequent annealing in air at 600 °C for 2 h. The hollow sea urchin-like α-Fe2O3 nanostructures with the diameters of 2–4.5 μm consist of well-aligned α-Fe2O3 nanorods with an average length of about 1 μm growing radially from the centers of the nanostructures, have a hollow interior with a diameter of about 2 μm. α-Fe2O3 nanocubes with a diameter of 700–900 nm were directly obtained by a hydrothermal reaction of FeCl3 at 140 °C for 12 h. The response Sr (Sr = Ra/Rg) of the hollow sea urchin-like α-Fe2O3 nanostructures reached 2.4, 7.5, 5.9, 14.0 and 7.5 to 56 ppm ammonia, 32 ppm formaldehyde, 18 ppm triethylamine, 34 ppm acetone, and 42 ppm ethanol, respectively, which was excess twice that of the α-Fe2O3 nanocubes and the nanoparticle aggregations. Our results demonstrated that the hollow sea urchin-like α-Fe2O3 nanostructures were very promising for gas sensors for the detection of flammable and/or toxic gases with good-sensing characteristics.