Development and characterization of WO3 nanoflakes for selective ethanol sensing

Despite an increasing demand for applications, the partial selectivity of metal oxide-based gas sensors limits their practical use in some cases, such as for ethanol detection. Consequently, the search for a performing ethanol sensor is still an open challenge. In this work, tungsten oxide nanoflake powders were synthesized by means of solvothermal technique in sight of ethanol sensing. The powders were characterized by X-ray diffraction, scanning electron microscopy, energy dispersion X-ray spectroscopy, textural and optical absorbance analyses and X-ray photoelectron spectroscopy and screen-printed as a paste on alumina substrates. Electrical characterization showed that these films responded well to ethanol and the conductance in the presence of this gas only decreased by about 20 % in mild humidity conditions, remaining constant over a range of 20–70 RH%. The operational temperature of the film was 250 °C, namely a lower level with respect to mostly used WO3 sensors in the literature. Marginal influence by typical interferents in some applications of an ethanol sensor was recorded. Among alcohols, the response to ethanol prevailed because of an interplay between catalytic properties of the sensing film and gas diffusivity in a porous medium.