Poly vinyl alcohol-CeO₂ nanocomposite films: a promising material for NO₂ sensors at high temperatures

Nanoparticles of CeO₂ were dispersed in Poly vinyl Alcohol to form nanocomposite films of various concentrations. Thick films of thickness around 100 μm were prepared by solution casting and pure PVA, PVA-2.5 wt% CeO₂ and PVA-25 wt% CeO₂ films were tested for their response as sensors to various gases. It was found that the PVA-2.5 wt% CeO₂ film showed the best response of nearly 40% increase in resistance to 100 ppm of NO₂ gas at 423 K. This indicated that it could be useful as a high temperature sensor for NO₂ gas. Three of the above samples were also prepared by spin coating technique as thin films of thickness 1 μm, 5 μm and 50 μm, on a glass substrate and tested for sensing action of the same gases at 3 ppm concentration. It was seen that 2.5 wt% CeO₂ film of 1 μm thickness gave the best response of 16% increase for NO₂ gas, amongst all the films. The increase in resistance of the films in the presence of NO₂ gas is due to chemisorption on the CeO₂ nano fillers and the mechanism seems to be effective even at low concentration of the filler. The results of sensing in these films are better than that of other similar materials and suggest that they can be used as high temperature sensors. (paper)