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

• Bi2O3-core/ZnO-shell nanobelt sensors were synthesized.
• The response of the core–shell nanobelts was far higher than that of pristine nanobelts.
• The gas sensing properties of the core–shell nanobelts were enhanced by UV irradiation.
• The enhanced ethanol sensing mechanism of the core–shell nanobelts is discussed.

Bi2O3 is highly sensitive to low concentrations of NO2 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 NO2 gas sensing properties of β-Bi2O3 nanobelts encapsulated with ZnO. Bi2O3-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 Bi2O3-core/ZnO-shell nanobelt sensors showed responses of 113–198% and 227–665% to 1–5 ppm NO2 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 Bi2O3 nanobelt sensors at 1–5 ppm NO2. The underlying mechanism of the enhanced response of the Bi2O3 nanobelts to NO2 gas by ZnO encapsulation and UV irradiation is discussed.