CO and ethanol dual selective sensor of Sm2O3-doped SnO2 nanoparticles synthesized by microwave-induced combustion

In the present investigation, the influence of Sm2O3 on the sensitivity and selectivity of SnO2-based sensors for selective detection of CO and C2H5OH in the presence of CH4 is studied. SnO2 doped with 2.0, 5.0 and 10.0 wt% Sm2O3 samples were prepared employing a microwave-induced solution combustion synthesis using tin chloride. The samples were characterized by SEM, EDS, XRD and BET. The results indicate that samarium oxide inhibits SnO2 crystal growth and enhances both sensitivity and selectivity of the sensors to CO and ethanol in the presence of methane. Upon addition of 2.0 wt% Sm2O3, the crystallite size of SnO2 reduces from 4.3 to 2.9 nm. As SnO2 is doped with 5.0 wt% Sm2O3 a significant enhancement in response to CO and ethanol was observed at various temperatures. At 200 °C, the 5.0 wt% Sm2O3-doped SnO2 sensor response to 300 ppm CO is 16 times higher than that to 300 ppm ethanol. On the contrary, 33 times higher response to ethanol is observed at 300 °C. The 5.0 wt% Sm2O3-doped sensor shows no response to methane up to 350 °C. This way, at different temperatures, the sensor is selective to either CO or ethanol in the presence of methane.