Light-activated gas sensing of Bi2O3-core/ZnO-shell nanobelt gas sensors

Abstract Bi 2 O 3 is highly sensitive to low concentrations of NO 2 in ambient air but almost insensitive to most other common gasses. On the other hand, its sensing performance and detection limit need to be improved before it can be used more widely. This study examined the NO 2 gas sensing properties of β -Bi 2 O 3 nanobelts encapsulated with ZnO. Bi 2 O 3 -core/ZnO-shell nanobelts were fabricated using a two-step process involving the thermal evaporation of Bi powders and the atomic layer deposition of ZnO. The core–shell nanobelts were 100 to 300 nm in diameter with lengths ranging from a few tens to a few hundreds of micrometers with a mean shell layer thickness of ~ 20 nm. Multiple networked Bi 2 O 3 -core/ZnO-shell nanobelt sensors showed responses of 113–198% and 227–665% to 1–5 ppm NO 2 at room temperature in the dark and under UV illumination, respectively. These responses were 1.2–1.9 and 2.4–6.3 times larger, respectively, than those of pristine Bi 2 O 3 nanobelt sensors at 1–5 ppm NO 2 . The underlying mechanism of the enhanced response of the Bi 2 O 3 nanobelts to NO 2 gas by ZnO encapsulation and UV irradiation is discussed.