Experimental and density functional study of the light-assisted gas-sensing performance of a TiO 2 -CoFe 2 O 4 heterojunction.

Toluene gas as a solvent is widely present in industrial production and indoor decoration, and can seriously harm human health even at low concentrations. Furthermore, toluene can be used as a typical biomarker for disease diagnosis. Therefore, the detection of toluene gas is very important. Herein, a hydrothermal method was used to successfully prepare a TiO 2 -CoFe 2 O 4 heterostructure for detecting toluene gas. The ultraviolet (UV)-visible diffuse reflectance spectra and photoluminescence spectra showed that the bandgap of the heterojunction was considerably shorter than those of pure TiO 2 and CoFe 2 O 4 , and the recombination of electron-hole pairs was inhibited. At the same time, the response value of the TiO 2 -CoFe 2 O 4 heterojunction was 10.5 for 20 ppm toluene at 219 °C, which was much better than those of pure TiO 2 and CoFe 2 O 4 . Moreover, its response value further increased under UV irradiation. In addition, density functional theory (DFT) was innovatively employed in this study to explain in detail how the heterojunction and UV irradiation can improve gas sensitivity through the calculation of the material energy band, adsorption energy, etc . This work provides a good reference for the preparation of high-efficiency and high-sensitivity gas sensors.