Effects of calcining temperature on SnO₂ sensors for CO and NO_x gases

Nitrogen oxides (NO_x) and carbon monoxide (CO) are among the most dangerous chemical species to human health present in the atmosphere. Acute CO toxicity leading to unconsciousness, respiratory failure or death can occur after 1 hr of exposure when ambient CO levels reach 1000 ppm, whilst increase of NO_x emissions can contribute to acid deposition, pollution of groundwater, eutrophication of surface waters, and tropospheric ozone and ecosystem damage. In this work, pure SnO₂ sensors for CO and NO_x were prepared by spin coating solutions derived from a washed Gel-precipitate followed by a calcining step. SnO₂ sensors of nanometer grain size prepared by this process showed good sensitivity to CO and NO_x gases. The increase of calcining temperature not only affected grain size and surface morphology, but also caused a decrease in sensitivity of the SnO₂ sensors.