Highly Efficient UV-Activated TiO/SnO Surface Nano-matrix Gas Sensor: Enhancing Stability for ppb-Level NO Detection at Room Temperature.

This study presents a new nanoporous TiO/SnO heterojunction for NO gas detection by using a two-step sol-gel process. The unique TiO and SnO nanoheterojunction matrix right on the film surface enables the TiO photocatalyst to absorb minimal UV power (3 μW/cm) and effectively transfer electrons to the SnO conduction band. The sensor detects NO and NO gases down to 4 ppb (response of 0.6%) and 10 ppb (response of 1.3%) at 1 V at room temperature. It also exhibits a fast recovery time (100 ± 40 s at 500 ppb NO), an improved response over a wide relative humidity range (10-60%), and a long lifetime over 30 days. The ultralow UV power required can be easily harvested from sunlight, eliminating the need for UV LEDs. XPS and SEM analyses indicated that the unique nanoporous TiO/SnO structure improves sensing performance, with oxygen vacancies playing a critical role in the NO gas sensing mechanism. This work demonstrated the highly efficient UV catalyst effect in sensors with the surface heterojunction matrix. The low-power ppb-level NO detection is suitable for environmental monitoring and respiratory disease detection.