CHAPTER 21: Nanostructured Metal Oxides for Sensing Toxic Air Pollutants

Recent developments in chemoresistive gas sensors for air monitoring applications are surveyed. Physical and chemical deposition methods for producing the gas sensitive layer are reviewed and the available binary, ternary and mixed metal oxides suitable for the detection of hazardous air pollutants are discussed. The gas sensing mechanism, which is based on the effect of chemisorption reactions on the resistivity of semiconductor metal oxides, is explained and microstructural and other factors affecting sensitivity and selectivity are examined in detail. Methods of increasing sensitivity and selectivity, particularly towards reducing gases, by the addition of metal dopants, are outlined. Outcomes of field tests to compare the performance of gas sensor devices with those of conventional air quality monitoring systems are summarised.