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The influence of ammonia on the optical absorption of polyaniline films obtained by the electrochemical method is studied. In the presence of ammonia, the optical spectra of a polymer are found to change due to the appearance of a new absorption band with a maximum at 2.07 eV and a simultaneous decrease in the intensity of bands at 1.57 and 2.91 eV. The kinetics of changes showing the presence of an isobestic point at 2.71 eV is elaborated. The results can be used to optimize the ammonia gas sensors for monitoring the biotechnological processes in the food industry and the environment.

In this paper we describe our studies of the influence of substrate nature and type of doping on the structure and sensor properties of thin films of ZnO, obtained on the surface of glass, quartz, pyroceramics, leuco-sapphire and oxidized silicon by thermo vacuum deposition. With X-ray investigation it is shown that the obtained films consist of nanocrystalline zinc oxide, regardless to the nature of the surface, and the best structural perfection characterized ZnO film on the surface of the quartz and glass. The sensitive properties of zinc oxide films to ethanol vapors can be greatly improved by introducing of doping impurities (Al or In), the highest sensitivity to ethanol was detected for the films of ZnO:Al on the quartz substrate. The proposed sensor can be used to monitor gas environments in the food industry and in the evaluation of alcohol in humans breathing.

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