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

Abstract

A free-standing, flexible, and semi-transparent MoO₃ nanopaper was fabricated using ultralong MoO₃ nanobelts (length ∼ 200 μm; 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 °C and 121 to 5 ppm trimethylamine (TMA) at 325 °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.