An indoor light-activated 3D cone-shaped MoS₂ bilayer-based NO gas sensor with PPb-level detection at...

Utilization of light to boost the performance of gas sensors allows us to operate sensor devices at room temperature. Here, we, for the first time, demonstrated an indoor light-activated 3D cone-shaped MoS2 bilayer-based NO gas sensor with ppb-level detection operated at room-temperature. Large-area cone-shaped (CS)-MoS2 bilayers were grown by depositing 2 nm-thick MoO3 layers on a 2'' three-dimensional (3D) cone-patterned sapphire substrate (CPSS) followed by a sulfurization process via chemical vapor deposition. Because the exposed area of MoS2 bilayers is increased by 30%, the CS-MoS2 gas sensor (GS) demonstrated excellent performance with a response of ∼470% and a fast response time of ∼25 s after exposure to 1 ppm of NO gas illuminated by ultraviolet (UV) light with a wavelength of 365 nm. Such extraordinary performance at room temperature is attributed to the enhanced light absorption because of the light scattering effect caused by the 3D configuration and photo-desorption induced by UV illumination. For NO concentrations ranging from 2 ppm down to 0.06 ppm, the CS-MoS2 GS demonstrated a stable sensing behavior with a high response and fast response time (470% and 25 s at 2 ppm NO) because of the light absorption enhanced by the 3D structure and photo-desorption under constant UV illumination. The CS-MoS2 GS exhibits a high sensitivity (∼189.2 R% ppm-1), allowing the detection of NO gas at 0.06 ppm in 130 s. In addition, the 3D cone-shaped structure prolonged the presence of sulfur vapor around MoO3, allowing MoO3 to react with sulfur completely. Furthermore, the CS-MoS2 GS using an indoor lighting to detect NO gas at room temperature was demonstrated for the first time where the CS-MoS2 GS exhibits a stable cycling behavior with a high response (165% at 1 ppm NO) in 50 s; for concentration as low as ∼0.06 ppm, the response of ∼75% in 150 s can be achieved.