Fe2O3/Carbon nanotube-based resistive sensors for the selective ammonia gas sensing

Iron oxide nanostructures with a dendritic like-pine tree morphology have been synthesized by a simple hydrothermal method. Hematite (α-Fe 2O3) is the only phase identified through a detailed TEM, XRD, Raman and XPS characterization. α-Fe2O3 nanostructures exhibit a highly insulating behavior, then more conductive α-Fe2O3/CNTs hybrid composites have been prepared by physical mixing of α-Fe2O3 nanostructures and carbon nanotubes (CNTs). Chemoresistive devices based on α-Fe 2O3 nanostructures for the selective monitoring of ammonia at low temperature have been then fabricated. The hybrid α-Fe 2O3/CNT composites have shown a higher variation of resistance upon exposure to NH3 compared to CNTs, due to a synergic action between the metal oxide and carbon nanotubes. The sensor developed exhibited a high selectivity to NH3. On the basis of results reported, a sensing mechanism involving a specific interaction of the target gas with the sensing layer surface has been proposed.