Enhanced amperometric acetone sensing using electrospun non-stoichiometric WO3-: X nanofibers

We report enhanced amperometric sensing response of electrospun tungsten oxide (WO3-x) nanofibers towards acetone with low concentrations (1.2-12.5 ppm) at 350 °C. Scanning and transmission electron microscopy (SEM and TEM) revealed the nanocrystalline nature of tungsten oxide nanofibers with a diameter in the range of 200-350 nm. X-ray diffraction (XRD) analysis showed a monoclinic crystal structure with oxygen vacancies, which are confirmed by X-ray photoelectron spectroscopy (XPS) providing an evaluation of the O : W ratio of 2.60. The excellent conductivity of tungsten oxide due to oxygen vacancies makes it a promising material for acetone sensing. Acetone sensing has been tested at various bias potentials (3-9 V), evidencing a variation of sensing response with voltage. The amperometric response has a three fold increase with an increase of the bias potential from 3 V to 9 V. The sensor shows a repeatability of ≥ 99% with an ability to detect low concentrations of acetone down to 10 ppb (calculated detection limit). The sensor also shows fast response kinetics and excellent selectivity when humidity and carbon dioxide were tested as cross-interference gas species.