Controllable fabrication, growth mechanism, and gas sensing properties of hollow hematite polyhedra

We report a facile and efficient fluoride ion-assisted hydrothermal route to prepare novel hollow hematite polyhedral architectures without any template or surfactant. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images reveal that the microparticles with empty interior are polyhedra. On the basis of time-dependent experiments, a multistage reaction mechanism for the formation of the hollow hematite polyhedra was proposed. This procedure brought into play the synergetic effects of the oriented attachment, recrystallization and etching. To demonstrate potential applications, we have fabricated a gas sensor from the as-synthesized hollow alpha-Fe2O3 cx polyhedra and investigated it for ethanol detection. Results show that the hollow alpha-Fe2O3 polyhedral sensor exhibits significantly improved gas sensitivity and selectivity performances in comparison with the compact alpha-Fe2O3 polyhedral structures.