An ultraselective and ultrasensitive TEA sensor based on alpha-MoO3 hierarchical nanostructures and the sensing mechanism

Flower-like, hierarchically nanostructured alpha-MoO3 was successfully synthesized via a one-step, template-free solvothermal route. Morphological characterization demonstrated that the nanostructures were hierarchically assembled by overlapping single-crystalline nanobelts with exposed (010) facets. These nanobelts, with a width of 40-60 nm and a thickness of 20-30 nm, grew radially from the core of the alpha-MoO3 flower. The growth mechanism of the alpha-MoO3 flower was speculated to be through oriented self-attachment of the nanobelts. The gas sensor based on alpha-MoO3 flowers showed an excellent sensing performance towards triethylamine (TEA) in terms of a high response (931.2) and excellent selectivity towards 10 ppm TEA. Especially, the detection limit was down to 0.001 ppm at a working temperature of 170 degrees C. The surface status of the alpha-MoO3 flowers before and after exposure to TEA at 170 degrees C was investigated by XPS. The probable oxidization product of TEA was analyzed by GC-MS. The MoO3 sensing mechanism could be interpreted as the transformation of triethylamine to vinylamine through two catalytic oxidation processes: the reactions with chemisorbed oxygen, and with lattice oxygen. The possibility relating to an enhanced gas sensing response of the three-dimensional (3D) flower-like alpha-MoO3 was discussed.