Detection of ammonia at ppm levels using titanium dioxide/polyaniline films deposited on plastic sheets

Resistive ammonia sensors are developed by using as sensing material nanostructured titanium dioxide thick films coated with polyaniline (PANI), applied on the top of copier grade transparency sheets. Due to the increased surface area and to the presence of the organic-inorganic interface, the PANI/TiO₂ sensors have improved sensitivity towards the target, and shorter transient times compared to resistive sensors based on PANI only. The PANI/TiO₂ sensors are found to reversibly change both their resistive and optical properties in response to ammonia. While concentrations below a few tens of ppm are not optically detectable, the PANI/TiO₂ sensors resistance is linearly related to the NH3 concentration in the range between 1 ppm and 10 ppm, with a sensitivity of about 1% for 1 ppm.