Wide bandgap mesoporous hematite nanowire bundles as a sensitive and rapid response ethanol sensor.

In this study, α-Fe₂O₃ nanowires were synthesized using mesoporous SBA-15 silica as the hard templates with the nanocasting method, and then mesoporous α-Fe₂O₃ nanowire bundles (NWBs) were separated from the well-dispersed α-Fe₂O₃ nanowires (NWs) by the centrifugation technique. Both samples were characterized by x-ray diffraction, transmission electron microscopy (TEM), nitrogen adsorption/desorption isotherm and UV-vis spectra. All results indicated that the α-Fe₂O₃ NWBs with mesoporous structure presented a higher BET surface area (95 m² g⁻¹) and wider bandgap (2.08 eV) than those of α-Fe₂O₃ NWs (32 m² g⁻¹ and 1.91 eV). The bandgap of α-Fe₂O₃ NWBs was in accordance with the bulk α-Fe₂O₃, while the BET surface area was much higher. The results from the gas-sensing measurement revealed that the α-Fe₂O₃ NWBs based gas sensor exhibited a high sensitivity of 21.7, fast response-recovery of 7.5 s and 1 s, and good selectivity to ethanol at 340 °C. The sensitivity (21.7) for ethanol of α-Fe₂O₃ NWBs was much better than that of the α-Fe₂O₃ NWs (12.2), which should be attributed to the higher BET surface area and wider bandgap of α-Fe₂O₃ NWBs. [ABSTRACT FROM AUTHOR]