Comparative studies on electrical properties of Polypyrrole based gas sensor

Polypyrrole (PPy) is one of the important conductive polymer (CP) that is widely used in gas sensing applications. It exhibits reversible changes in its direct current (DC) resistance on exposure to variety of organic vapors and gases, but the environmental stability of its resistive property is found poor. Hence polypyrrole based gas sensor is designed and its electrical properties against ethanol as an analyte has been studied. Polypyrrole is electrodeposited on interdigital gold electrode structure with potassium chloride (1M KCl) as an electrolyte using chronocoulometry. Electrical impedance spectroscopy technique is used to study electrical properties of the sensor over a frequency range 10 Hz to 2 MHz. The sensor response is monitored by measuring the changes in its impedance i.e., capacitance and resistance of the sensor upon exposure to organic vapor molecules. It is observed that the capacitive property of the sensor is more sensitive to the ethanol than its resistive property. Effect of aging on the electrical properties of the sensor is also studied and found that the capacitance has less effect with aging than its resistive property.