Organic Electrochemical Transistor with Molecularly Imprinted Polymer-Modified Gate for the Real-Time Selective Detection of Dopamine

Because of their low operation voltage, high transconductance, and good aqueous compatibility, organic electrochemical transistors (OECTs) have been widely applied in the sensing of small redox-active molecules such as dopamine. However, selective detection of dopamine (DA) can be challenging since its sensing mechanism relies on the gate voltage offset caused by the redox chemistry at the gate electrode. To introduce selectivity toward dopamine detection, a polypyrrole film was electrochemically deposited on the Pt gate electrode with the presence of dopamine as a template and then overoxidized in an alkaline solution. The resultant OECT sensor with an overoxidized MIP (o-MIP/Pt) gate shows a similar detection limit of ∼34 nM as compared to the device with a bare Pt gate. At the same time, when compared to the drain current response of a representative interferent, ascorbate (AA), a good selectivity of DA/AA signal ratio of larger than 5 can be achieved in the concentration range between ∼0.4 and ∼10 μM, whereas OECT sensor with bare Pt gate shows little selectivity toward DA. The selectivity of the OECT sensor toward DA can be maintained in the copresence of 1-fold DA (∼0.4 μM) and 10-fold AA (∼4 μM), regardless of the order of the additions.