Active sites on the surface of nanocrystalline semiconductor oxides ZnO and SnO2 and gas sensitivity

Resumo

The data on active sites on the surface of nanocrystalline semiconductor oxides ZnO and SnO₂ are reviewed. Their interrelation to the gas sensitivity of the materials toward the main air pollutants, viz., CO, NO₂, NH₃, and H₂S, is analyzed. The influence of the synthesis conditions, microstructure parameters, content of dopant impurities, and the presence of catalytic modifiers on the concentration of various active sites on the oxide surface is considered. Relationships between the concentration of the surface sites and sensitivity of the oxides to gases with various chemical properties are revealed. The active sites responsible for the formation of a sensory signal upon the selective interaction with molecules of the detected gases are determined.