Room-temperature ppb-level SO₂ gas sensors based on RGO/WO₃ and MWCNTs/WO₃ nanocomposites

ppb-level SO₂ gas sensors for use at room temperature were fabricated using an in situ one-pot polyol method combined with metal organic decomposition (MOD) of nanocomposite films of multi-walled carbon nanotubes/WO₃ (MWCNTs/WO₃) and reduced graphene oxide/WO₃ (RGO/WO₃) on an alumina substrate. Comparative gas sensing results showed that the SO₂ gas sensor based on the RGO/WO₃ nanocomposite film exhibited a higher response compared with the MWCNTs/WO₃ nanocomposite film and pristine WO₃ film, sensing SO₂ gas at very low (ppb-level) concentrations at room temperature. The SO₂ gas sensor based on the RGO/WO₃ nanocomposite film also had fast response and recovery times, good reproducibility, and the lowest detection limit. The formation of new conducting pathways and the spread of the depletion layers at the interface of the doped MWCNTs or RGO and the WO₃ matrix upon interaction with SO₂ gas were responsible for the enhanced response.