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.
