Impedimetric and Capacitive Transducer Platform for Chemical Sensors Based on Electrodeposited Polyaniline Thin Films
Hugo José Nogueira Pedroza Dias Mello, Marcelo Mulato
Abstract
Analytical sensors for rapid and faithful responses allowing for miniaturization have increased in relevance. Electrochemical methods are fulfilling such requirements through multiplexable and effective detection. An electrochemical pH sensor based on galvanostatically electrodeposited polyaniline (PANI) thin films is here presented. Electrochemical impedance spectroscopy (EIS) and capacitance spectroscopy (ECS) are analyzed as transduction stages. The capacitive properties of PANI applied in chemical sensors are novel. Sensitivity, linearity, and hysteresis were studied for both electrochemical settings. The impedimetric/capacitive electrochemical setup provides information about the polymeric samples’ conductivity, impedance, double layer properties, and electrochemical capacitance. The oxidation state of the PANI layer directly influences its response in each sensor setup through the protonation potential and electronic density of the PANI samples. PANI thin films produced with a deposition current density of 0.5 mA/cm2 presented the largest sensitivity for the impedimetric setup (12.7 ± 2.2% per pH and linearity of 91.7%) while the PANI thin films produced at 1.0 mA/cm2 presented the largest sensitivity for the capacitive setup (15.3 ± 1.7% per pH and linearity of 94.1%). Development of distinct electrochemical sensor platforms with the same material is possible by controlling the oxidation state of the samples. The sensor is suitable to be used in many different applications such as environmental, food, and health biosensors based on chemical measurement.