Optimized PVA-(ZnO)x-(PANI)1−x nanocomposites: characterization and humidity sensing application

Abstract This work presents an effort to study the potential of ternary PVA/ZnO/PANI nanocomposite for humidity sensing applications. Easily-peeled-off films of the ternary system were formed by the solution casting method and characterized. FTIR manifested the uniformity of the synthesized films and the existence of both polyaniline and ZnO functional groups in the relevant PVA host matrix. Characteristic absorption bands of PVA were overlapped with some characteristic bands of polyaniline. XRD patterns show the typical semicrystalline peak for the pristine PVA. The XRD analysis did not demonstrate any crystalline peaks for ZnO due to the capping-off effect of the PVA macromolecule. Energy dispersive X-ray mapping analysis and SEM micrographs manifested a homogeneous distribution of ZnO and PANI particles and a smooth yet dense film appearance. A study of electronic transitions and band gap displayed that the value of the band gap varies based on component concentration with the lowest value for the film of equal concentration of both ZnO and polyaniline. The humidity sensing behavior of the films was explored at different frequencies. The most variation in impedance was reached at 500 Hz, while the impedance variation at 50 Hz is the best from the performance point of view, where the relation between the impedance and relative humidity is linear. Samples F3 [PVA (ZnO) 0 . 7 (PANI) 0.3 ], and F4 [PVA (ZnO) 0 .5 (PANI) 0.5 ] revealed the highest sensitivity among other tested samples. The measured hysteresis for the F3 and F4 samples were 1.38E + 05 MΩ/RH and 1.55E + 05 MΩ/RH, respectively. Impedance and complex impedance spectroscopy measurements confirmed that the film F3 revealed the highest sensitivity among the other tested samples. The proposed structure of the sensor can be employed for real-life applications since it can be easily coupled with electronic read devices and its overall functionality.