Application of electrical impedance spectroscopy and amperometry in polyaniline modified ammonia gas sensor

Accurate and fast detection of ammonia gas is a highly desirable requisite in environmental gas analysis, the automotive industry, the chemical industry and for medical applications. In this study a cost effective and portable electrochemical ammonia (NH3) gas sensor is reported. The sensor was based on polyaniline (PANI) nanofibres employing the techniques of electrical impedance spectroscopy with frequency response analysis and amperometry. PANI is well known for its interaction with ammonia gas. This conducting polymer (PANI) of the semi-flexible rod polymer family, is unique due to its easy synthesis method, environmental stability, and simple doping/dedoping chemistry. PANI was synthesized and characterized by SEM, FTIR, XRD and AFM studies. The experimental data were used to explain, characterize and standardize the changes, upon exposure to ammonia gas, in the resistive and capacitative components set up in the PANI electrochemical cell. This nondestructive chemical-gas sensor was characterized by high sensitivity, a wide range of measured concentrations (0–20 ppm) in case of EIS and (2.5–20 ppm) in case of amperometry, reliability and reproducibility of the sensing data.