In-situ generated TiO2/α-Fe2O3 heterojunction arrays for batch manufacturing of conductometric acetone gas sensors

A highly sensitive and selective acetone gas sensor has been fabricated successfully by designing n-n heterojunction consisting of TiO 2 nanorods and α -Fe 2 O 3 branches. The structure and morphology of the TiO 2 / α -Fe 2 O 3 nanocomposites were examined via X-ray diffraction and scanning electron microscopy, respectively. TiO 2 nanorod (with the diameter about 42 nm) arrays were in-situ generated on the surface of Al 2 O 3 ceramic tubes by a simple hydrothermal process. In addition, α -Fe 2 O 3 branches grew on TiO 2 stems successfully in the second hydrothermal process. These nanorod branches had a relatively uniform length, which could be tunable by changing the concentration of iron precursor. The gas sensing properties of the pristine and α -Fe 2 O 3 branches-decorated TiO 2 nanorods sensors with regard to acetone gas were investigated. The results indicated that the sensor based on TiO 2 / α -Fe 2 O 3 heterostructures measured at 225 °C had a higher response of 21.9 toward 100 ppm of acetone gas which was about 9 times higher than pristine TiO 2 nanorods sensor. The dominant mechanism for enhanced sensing properties were discussed in detail with the semiconductor depletion layer model and TiO 2 / α -Fe 2 O 3 n–n heterojunction theory.