Diameter controlled synthesis of tungsten oxide nanorod bundles for highly sensitive NO2 gas sensors

Abstract Attempts to improve the performances and cost effectiveness of gas sensors for practical applications have led to the development of advanced nanostructured materials, which enabled the fabrication of highly sensitive and selective sensing devices. This study introduced the diameter controlled synthesis of scalable and large-quantity nanoporous tungsten oxide nanorod bundles for highly sensitive NO2 gas sensor applications. The diameter controlled nanoporous tungsten oxide nanorod bundles were synthesized by a facile hydrothermal method. The morphologies of the nanorod bundles were controlled by varying the amount of pluronic P123 surfactant. Gram quantities of the nanoporous tungsten oxide nanorod bundles were easily obtained and found effective in the fabrication of scalable gas sensors using a spray technique. Investigation on the gas sensing properties demonstrated that the nanoporous tungsten oxide nanorod bundles based gas sensor exhibited a relatively high response due to their small size (~20 nm) and nanoporous structure, which provided large adsorption sites and accelerated the accession of the analytic gas molecules. The developed sensor enabled the monitoring of highly toxic NO2 gas at low concentrations among other contaminants. The response to 5 ppm NO2 was 126-folds higher than that to 200 ppm NH3. The sensor also exhibited outstanding stability when operated at 250 °C. No distortion in sensor response was observed after five measurement cycles.