Determination of Nitrogen Dioxide by Thin-Film Chemical Sensors Based on CdxPb1 –xS

Resumo

The results of a study of sensors based on thin semiconductor films of Cd_xPb_1 – xS solid solutions intended for the determination of nitrogen dioxide in air are described. For a comparative assessment of the composition, morphology, and functional properties of the films, they were synthesized from reaction mixtures containing various cadmium salts. It was found that the maximum response is provided by layers obtained using cadmium acetate, in which the composition of the solid solution differs in the maximum supersaturation level in CdS. The films were formed of crystallites with average sizes of ~200 nm. When the concentration of nitrogen dioxide in air was 0.05‒200 mg/m³, the relative change in the ohmic resistance of sensors ranged from 8 to 80%. It was shown that the threshold concentration of NO₂ in air was about 0.02 mg/m³. The reversible nature of the gas adsorption process opens a possibility for the creation of reusable chemical sensors based on Cd_xPb_1 – xS films, differing in a relatively low threshold concentration of NO₂ detection and selective response in the presence of significantly higher concentrations of O₂, CO₂, and H₂.