Ethanol sensors based on Pt-doped tin oxide nanopowders synthesised by gel-combustion

The ethanol sensing properties of SnO2 powders prepared by a gel-combustion method have been investigated. SnO2 powders with different average crystallite size, D, ranging from 6 up to 100 nm, were synthesized by this process starting from metallic tin as raw material and citric acid and/or urea as fuel substances. The average crystallite size of the synthesized powders was found to depend on the nature and loading of the fuel substance used in the combustion process. Thick film sensors based on the gel-combustion SnO2 powders, annealed at 600 ◦C, have shown good sensitivity to low concentrations of ethanol (50–200 ppm). The smaller particles have shown a higher sensitivity than the bigger ones. At the addition of 1 wt% Pt, a remarkable enhancement of the sensitivity to C2H5OH and response and recovery time was observed for the sample with smaller SnO2 particles. Pt was instead found to suppress CO sensitivity, thus increasing the selectivity towards ethanol.