In-situ generated TiO_2/α-Fe_2O_3 heterojunction arrays for batch manufacturing of conductometric acetone gas sensors

摘要

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_2O_3 branches. The structure and morphology of the TiO_2/α-Fe_2O_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_2O_3 ceramic tubes by a simple hydrothermal process. In addition, α-Fe_2O_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_2O_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_2O_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_2O_3 n-n heterojunction theory.