Low-temperature NO2 sensor based on γ-In2Se3/In2O3 nanoflower heterojunction

The γ-In2Se3/In2O3 nanoflower-like heterojunctions were synthesized by solvothermal treatment followed by thermal oxidation in Air. The nanoflower-like γ-In2Se3/In2O3-based chemiresistive-type sensor showed a significantly enhanced response to NO2 at an operating temperature of 170°C. The sensor achieves a response of 2.69 to 0.2 ppm NO2 at 170°C. The sensor exhibits remarkable selectivity to several possible interferents such as carbon monoxide, ammonia, formaldehyde, acetone, methanol, and toluene, and good stability at 170°C. The nanoflower structure increases the specific surface area and introduces more active sites, which improves the sensitivity of the sensor to NO2. The heterojunction formed between γ-In2Se3 and In2O3 improves the charge carrier transfer between NO2 gas molecules and sensing materials, thereby increasing the response of the sensor to NO2. Density functional theory was used to elucidate this sensing mechanism, and it was found that improved sensing performance is mainly due to heterojunction formation, which increases the adsorption energy of nitrogen dioxide molecules on a sensing material surface and facilitates charge transfer between molecules.