Gas-sensing properties of tin oxide doped with metal oxides and carbon nanotubes: A competitive sensor for ethanol and liquid petroleum gas

SnO2 doped with metal oxides such as PtO2, PdO, La2O3 CuO, and Fe2O3 and multi-walled carbon nanotubes (MWCNTs) thin films were prepared by the sol–gel method. Thin film gas sensors were fabricated by spin-coating the sol onto interdigitated microelectrodes. The microstructure and morphology of the materials were characterized by XRD, FE-SEM, and TEM. The results reveal that their SnO2 particle size is lower than 10 nm, and the MWCNTs doping is well embedded in the SnO2 matrix. The response of all the sensors was studied for different concentrations of ethanol and liquid petroleum gases (LPG) and at different operating temperatures. Comparative results reveal that the (1 wt%) PtO2-doped SnO2 sensor exhibits higher sensitivity to ethanol gas and LPG than the sensors doped with the other dopants. Especially, the (1 wt%) PtO2-doped SnO2 sensor shows higher selectivity to ethanol gas over LPG, while the (0.1 wt%, 20 < d < 40 nm)-doped SnO2 shows higher selectivity to LPG over ethanol gas in the same testing conditions.