Large-sized alpha-MoO3 layered single crystals for superior NO2 gas sensing

Molybdenum trioxide (MoO3) has attracted considerable research interest due to its unique structural and electronic properties. Herein, we report a monolithic and scalable NO2 gas sensor based on centimeter-sized single-crystalline alpha-MoO3 synthesized via vapor phase transport method. A combination of advanced characterization probes were utilized to study morphology, composition and crystalline structures of the as-synthesized crystals. At the optimal operating temperature of 100 ?degrees C, the centimeter-sized alpha-MoO3 single crystal based sensor shows an outstanding sensitivity towards NO2 with a limit of detection as low as 5 ppb, as well as superior selectivity and reversibility. The scalability and the intrinsic sensing response are further demonstrated by microscale sensor devices fabricated on individual exfoliated alpha-MoO3 nanoribbons. Our study presents promising opportunities to develop a high-performance gas sensing platform based on crystalline alpha-MoO3 to enable monolithic, scalable and integrable sensing technologies.