Monodispersed hollow α-Fe2O3 ellipsoids via [C12mim][PF6]-assistant synthesis and their excellent n-butanol gas-sensing properties

Monodisperse α-Fe2O3 hollow ellipsoids have been assistantly fabricated via small amount of [C12mim][PF6] (IL) addition from a simple one-pot method based on hydrothermal treatment of FeCl3·6H2O, followed by calcination at various temperatures. The phase and microstructure of the products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption-desorption techniques. Further studies reveal that both calcination temperature and the amounts of IL have a strong effect on the structures. The well known Ostwald ripening process is responsible for the transformation from solid ellipsoids to hollow ellipsoids. The gas sensors based on the as-synthesized hollow α-Fe2O3 ellipsoids calcined at 300 °C exhibited not only high response, short recovery time and good stability to 100 ppm n-butanol at 217 °C, but also low detection limit (0.1 ppm) compared with those under higher calcination temperature and the products obtained without ILs-addition. IL-loading α-Fe2O3 hollow ellipsoids could be a promising candidate for highly sensitive n-butanol gas sensors.