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 TiO2 nanorods and alpha-Fe2O3 branches. The structure and morphology of the TiO2/alpha-Fe2O3 nanocomposites were examined via X-ray diffraction and scanning electron microscopy, respectively. TiO2 nanorod (with the diameter about 42 nm) arrays were in-situ generated on the surface of Al2O3 ceramic tubes by a simple hydrothermal process. In addition, alpha-Fe2O3 branches grew on TiO2 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 alpha-Fe2O3 branches-decorated TiO2 nanorods sensors with regard to acetone gas were investigated. The results indicated that the sensor based on TiO2/alpha-Fe2O3 heterostructures measured at 225 degrees C had a higher response of 21.9 toward 100 ppm of acetone gas which was about 9 times higher than pristine TiO2 nanorods sensor. The dominant mechanism for enhanced sensing properties were discussed in detail with the semiconductor depletion layer model and TiO2/alpha-Fe2O3 n-n heterojunction theory.