Polypyrrole/porous anodized aluminum oxide composite device for ammonia gas sensing

Abstract

In this study, a gas sensor device was fabricated using the conducting Polypyrrole (Ppy) coated on porous anodized aluminum oxide (PAAO) which acted as substrate. The Ppy was synthesized by the chemical oxidation polymerization method. The oxidation of aluminum is carried out using anodization method technique to develop a capacitive substrate that displays large resistance. Afterwards, the substrate is subjected to polypyrrole coating to develop a sensing material for the gas sensor for ammonia detection based on impedimetric response. For gas sensing application, device was fabricated on interdigitated electrode for which prior electrical characterization was carried out via impedance spectroscopy in order to understand its gas sensing characteristics. The values obtained for the resistance and capacitance using the Z′′ spectrum are 13.36 × 106 Ω and 9.08 × 10−11 F, respectively. The ammonia concentration range in which the ammonia sensing was observed through the change in the impedance (Z) or resistance (R) extends from approximately 05 to 95 ppm. The dynamic response and recovery time of Ppy/PAAO based sensor for ammonia gas was ∼6 s which also displayed significant reproducibility with ammonia concentration when subjected to the adsorption–desorption cycles whereas sensitivity of polypyrrole based ammonia sensor was found to be ∼1.74 × 106 Ω per ppm change at 100 Hz, respectively.