Figure 4. Working principle of the selective all-PEDOT:PSS OECT.

The oxidation reactions of AA, DA and UA take place at different electrochemical potentials and, consequently, also at different gate potentials in an OECT. When a faradic process occurs at the gate electrode, more cations are injected in the PEDOT:PSS of the channel leading to an extraction of holes from the conductive polymer. Consequently, the gate effect is enhanced by a rise of the trans-conductance value. The OECT sensor indentifies the contributions of different analytes as peaks in the trans-conductance plot.