alpha-Fe2O3 nanotubes that can be used as chemical sensors (see Figure) are fabricated by a novel carbon nanotube (CNT) templated synthesis. CNTs are coated with a continuous layer of Fe2O3 nanoparticles by the decomposition of Fe(NO3)(3) in a supercritical CO2/ethanol solution. Subsequent removal of the CNTs gives alpha-Fe2O3 nanotubes that are highly sensitive to H2S, which makes them attractive materials for chemiluminescent H2S sensors.