Polyaniline/poly(ethylene terephthalate) film as a new optical sensing material

Thin polyaniline (PANI) films are known as good optical gas sensors to ammonia but have weak mechanical properties that limit their industrial applications. To improve these properties we have developed new robust transparent PANI based composite films using the combination of aniline polymerization inside a thin (∼1 μm) surface layer of a poly(ethylene terephthalate) (PET) film and specific chemical treatments. We demonstrate that the final PANI/PET composite films have an increased surface area; give strong, fast and reversible optical sensor responses to ammonia or formic acid gas mixtures when in doped or dedoped PANI states respectively. Specifically in case of ammonia–air gas mixtures we demonstrate that the doped (PANI–HCl)/PET films give linear optical responses to ammonia gas in concentration ranges of 5–200 ppm and 200–920 ppm. The undoped PANI/PET films give linear optical response to formic acid in the concentration ranges of 15–200 ppm and 200–1600 ppm.