Investigating the physicochemical and optical properties of PANI and PANI-ZnO thin films for an efficient ammonia sensor at ambient conditions

Polyaniline (PANI) and polyaniline-zinc oxide (PANI-ZnO) nanocomposite thin films have been developed to detect NH₃ gas. The physicochemical and optoelectronic properties of developed thin films were explored using X-ray diffraction (XRD), field effect scanning electron microscope (FESEM), ultraviolet-visible spectroscope (UV–Vis.) and Fourier transform infrared spectroscope characterization techniques. Structural and morphological properties were studied via XRD and FESEM characterization, respectively. The developed thin films exhibited an excellent response towards the target NH₃ gas with outstanding sensitivity, selectivity, linearity, and stability which were studied using the chemiresistive modality at room temperature. Compared to PANI thin film, PANI-ZnO thin films exhibit a 9-fold increment in sensing response with an R² value of 0.997. PANI film achieved a response time of ~70 s and a recovery time of ~100 s for 10 ppm NH₃ gas. PANI-ZnO thin films exhibit a response time of ~45 s and a recovery time of ~70 s for the same concentration. All developed films respond to a 5-ppm concentration of NH₃ considered a lower detection limit. The PANI-ZnO thin films show higher stability than PANI films measured in 45 days. Thus, the developed sensors confirmed their potential for the detection of NH₃ gas.