Hybrid cross-linked polyaniline-WO3 nanocomposite thin film for NO(x) gas sensing

Nanocomposite thin film of cross-linked polyaniline [CLPANI, derived from polyaniline and aniline formaldehyde condensate (AFC)] and WO3 has been fabricated using vacuum thermal evaporation technique. X-ray diffraction pattern of as-grown film shows broad reflections of polymer along with mixed reflection of nonhydrated and hydrated WO3 nanoparticles. The scanning electron microscopy studies reveal uniform dispersion of WO3 nanoparticles in CLPANI network. The broadening of the absorption band at 320 nm corresponding to PANI and AFC-WO3 nanocomposite is attributed to cross-linking between the polymeric units. The NO(x) gas sensing characteristics of vacuum deposited CLPANI-WO3 thin film have been studied by measuring the change in resistance with respect to time. The sensor can be operated at room temperature, resulting in extended shelf life of the sensor. The response time and recovery time of the sensor operated at room temperature have been experimentally determined as 30 s and 11 minutes respectively.