High-performance UV-activated room temperature NO2 sensors based on TiO2/In2O3 composite

Porous TiO2 nanoparticle (NPs)-embedded In2O3 nanofibers (NFs) were synthesized using electrospinning for fabricating room temperature (RT) nitrogen dioxide (NO2) gas sensors. The diameter of the porous polycrystalline TiO2/In2O3 nanofibers was 60 nm and they were composed of sub-grains of average size 10-15 nm. Compared to pure In2O3 nanofibers, the TiO2/In2O3 nanofibers exhibited higher response, shorter response and recovery times, better reproducibility, and improved selectivity to NO2. The response of the TiO2/In2O3 composite to 5 ppm NO2 at RT under ultraviolet (UV) irradiation was 49.29, which was 8.96 times higher than that of pure In2O3. Even for a high relative humidity (RH) of 80%, the response of the TiO2/In2O3 composite to 5 ppm NO2 was approximately 41.25. The enhanced NO2 sensing performance of the composite can be ascribed to the formation of the TiO2/In2O3 n-n heterojunction, porous structure of the nanofibers, enhanced light absorption, and large number of O vacancies.