Liquid flame spray fabrication of WO3-reduced graphene oxide nanocomposites for enhanced O3-sensing performances

WO 3 is one of the inspiring sensing materials that show high response to O 3 ; an efficient fabrication of WO 3 film with incorporation of complementary additives is essential for enhanced sensitivity. Here we report film deposition by liquid flame spraying, characterization of nanostructured WO 3 -reduced graphene oxide (rGO) composites and their gas-sensing activities to O 3 . The starting feedstock was prepared from WC l6 and rGO for pyrolysis synthesis by flame spraying. Nano-porous WO 3 -rGO films were successfully fabricated and characterized by transmission electron microscopy , field emission scanning electron microscopy , Raman spectrometry , thermal analyses and X-ray diffraction. Nanosized WO 3 grains exhibited oriented nucleation on rGO flakes whereas rGO retained intact its nano-structural features after spraying. Constrained grain growth of WO 3 of 60–70   nm in size was realized in the rGO-containing films with as compared to ~220   nm in the pure WO 3 film. The WO 3 -rGO film sensors showed quicker response to O 3 and faster recovery than rGO-free WO 3 film sensors. Addition of rGO in 1.0   wt% or 3.0   wt% in the films caused a significantly reduced effective working temperature of the film sensors from ~ 250   °C to ~ 150   °C.