In2O3–ZnO nanotubes for the sensitive and selective detection of ppb-level NO2 under UV irradiation at room temperature

In 2 O 3 –ZnO nanotubes were prepared by a solvent thermal method using electrospun indium nitrate–polyvinyl pyrrolidone [In(NO 3 ) 3 –PVP] nanofibers as a sacrificial template. The sensing properties toward NO 2 of this kind of new emerging sensing material were explored. Compared with as-electrospun In 2 O 3 nanofibers, the In 2 O 3 –ZnO composite nanotubes exhibited higher responses and better selectivity to NO 2 . The response of the In 2 O 3 –ZnO nanotubes to 500 ppb NO 2 at room temperature (RT, 25 °C) under UV irradiation was as high as to 32.73, which was 3.33 times higher than that of the In 2 O 3 nanofibers. Moreover, even under a high relative humidity of 80%, the RT NO 2 response of the In 2 O 3 –ZnO composite nanotubes can still reach up to 3.50–500 ppb. The enhanced NO 2 sensing characteristics were mainly ascribed to the formation of In 2 O 3 –ZnO n–n heterojunctions , the enhanced light absorption, and the increased oxygen vacancy proportion. The results suggested that In 2 O 3 –ZnO nanotubes had good potential for the selective and sensitive detection of ppb-level NO 2 at RT.