GAS SENSORS BASED ON ORGANIC-INORGANIC NANOCOMPOSITES

Abstract

The use of nanocrystals with large specific surface in sensor structures provides their high sensitivity to molecules of adsorbed gases. The aim of the work was to create sensor elements based on composite films of poly-3,4-ethylenedioxythiophene (PEDOT) in combination with nanocrystals of porous silicon (PS) and zinc oxide (ZnO) and to study the effect of adsorption of ammonia, ethanol and acetone molecules on the electrical parameters of the PEDOT-PS-ZnO structure.To produce film of PEDOT-PS-ZnO hybrid composite, 1% suspension of PEDO-PSS, zinc oxide with a particle size of 100 nm (Sigma-Aldrich Co, USA) and PS nanocrystals, obtained by electrochemical etching of silicon wafer were used. Research of adsorption-desorption processes in the composite films was carried out by measuring their electrical parameters at different concentrations of the analyzed gases. To evaluate the sensor properties, the adsorption sensitivity of the composite films was calculated and their dynamic characteristics were studied.Increase of electrical resistance of nanocomposite due to adsorption of ammonia, ethanol and acetone molecules was registered. The almost linear dependence of the resistance on the concentration of ammonia and acetone was observed. It is a significant advantage in developing of the gas sensors. The maximum sensitivity of the sensor elements is in the range of 1-2% concentration of the analyzed gases and the response time is 60-80 s. The films with higher content of PS nanocrystals were more sensitive to molecules of ammonia and ethanol, and the films containing more nanoparticles of ZnO - to molecules of acetone. To control functional parameters of the sensor films, the content ratio of semiconductor nanoparticles in hybrid composite can be changed.The combination of nanoparticles of porous silicon and zinc oxide provides not only an increase in working surface area of sensors, but also high sensitivity and selectivity to the ammonia, ethanol and acetone molecules. The obtained results can be used to create effective analyzers of gases.