Molybdenum trioxide nanopaper as a dual gas sensor for detecting trimethylamine and hydrogen sulfide

A free-standing, flexible, and semi-transparent MoO3 nanopaper was fabricated using ultralong MoO3 nanobelts (length similar to 200 mm; width 200-400 nm), and its gas-sensing characteristics were investigated. The sensor exhibited high responses (resistance ratio) of 49 to 5 parts per million (ppm) hydrogen sulfide (H2S) at 250 degrees C and 121 to 5 ppm trimethylamine (TMA) at 325 degrees C with excellent gas selectivity, demonstrating its dual function for gas detection. Moreover, the sensor showed promising potential for the all-in-one detection of three representative offensive odors (TMA, H2S, and NH3) simply by tuning of the sensing temperature. This particular performance is attributed to the high chemical affinity of MoO3 to H2S and the acid-base interaction between basic TMA/NH3 and acidic MoO3. The mechanism underlying the control of gas selectivity by modulating the sensor temperature was investigated by Diffuse Reflectance Infrared Fourier Transform (DRIFT) measurements.