Study of surfactant adsorption onto electropolymerized o-phenylenediamine film by using a capacitive sensing method

Abstract

A capacitive sensing device has been designed by using electropolymerized o-phenylenediamine (PPD) film as an isolating layer and has been applied successfully to study the adsorption of Tween 80 onto the PPD film surface. The PPD was prepared with a cyclic voltammetry method and the thickness of the PPD film was estimated as about 110 ± 10 nm. The properties of the PPD insulating film were characterized with an electrochemical impedance method. The results show that the equivalent circuit model of this device is Randles type. The adsorption process of Tween 80 onto the PPD film was detected with the electrochemical impedance method. The result implies that the adsorption model of Tween 80 onto the PPD film appeared as pseudo Langmuir type and the adsorption equilibrium constant was 213.87 (dm3 g−1). We expect that the capacitive sensor will be a useful tool for investigation of interface action.