Indoor Light-Activated 3D Cone-Shaped MoS2 bilayers-based NO Gas Sensor with PPb-Level Detection at Room-temperature
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 bilayers-based NO Gas sensor with ppb-level detection operated at room-temperature. A 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 an 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 high and fast response (470 % and 25 s at 2 ppm NO) because of the light absorption enhanced by the 3D structure and photo-desorption under the constant UV illumination. The CS-MoS2 GS exhibits a high sensitivity (~189.2 R%/ppm), 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, CS-MoS2 GS using an indoor lighting to detect NO gas at the room temperature was demonstrated for the first time where the CS-MoS2 GS exhibits a stable cycling behavior with 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.