Room Temperature Operating, Fast and Reusable Polyaniline Sensor Synthesized Ultrasonically Using Organic and Inorganic Acid Dopants

In this paper we report a simple, green method for synthesis of polyaniline (PANI) nanoparticles by chemical oxidative polymerization with the assistance of ultrasonic irradiation. The polyaniline nanomaterials were synthesized with several organic acid dopants (tartaric acid (C4H6O6) and oxalic acid (C2H2O4)) and inorganic acid dopants (hydrochloric acid (HCl) and perchloric acid (HClO4)). A comparative study of the effect of the organic and inorganic acid dopants on the sensing properties of PANI for ammonia (NH3) vapors at room temperature was performed. It was observed that the electrical properties of the doped PANI depended on the type of the acid dopant. A remarkable change in resistance was observed upon doping with the different acid dopants. Structural and morphological studies and composition analysis were performed by UV-visible, FTIR, XRD and SEM techniques. The highest conductivity was obtained for PANI with HClO4 acid dopant while the lowest conductivity was obtained for PANI with tartaric acid dopant. The results showed that PANI doped with tartaric acid was an excellent sensor with fast response time and an enhanced sensitivity (26.1% for 5 ppm and 56% for 100 ppm) for NH3 gas at room temperature. PANI doped with organic acids showed faster recovery following NH3 treatment as compared to PANI doped with inorganic acid dopants. The PANI doped with tartaric acid sensor showed excellent stability for 350 days. In summary ultrasonic irradiation and the nature of the dopants showed significant effects on enhancing the sensing performance.