Turning on High‐Sensitive Organic Electrochemical Transistor‐Based Photoelectrochemical‐Type Sensor over Modulation of Fe‐MOF by PEDOT

Abstract Low‐gate voltages can make large modulations in the drain current. Accordingly, organic electrochemical transistors (OECTs) have attracted considerable interest as amplifying transducers. The use of OECTs in combination with electrochemical analysis promises to promote sensing performance. Herein, an OECT‐based photoelectrochemical‐type (OECT‐PEC) sensor is constructed based on the photo‐induced potential generating variation in the drain current. The as‐constructed OECT‐PEC sensor has high sensitivity because the device incorporated a sensor and an amplifier, providing the benefits of a PEC sensor and an OECT. In addition to the advantages of excellent signal amplification and ease of miniaturization, background signals are also effectively reduced, and possible interferences from electroactive substances are avoided due to the separation of light excitation and the electric output. The OECT‐PEC sensor integrates poly(3,4‐ethylenedioxythiophene) (PEDOT)‐modulated Fe‐metal organic framework (Fe‐MOF) nanocomposites as the photo‐active gating material and poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the channel material which exhibits a good photocurrent response from the gate electrode and a corresponding 100‐fold expansion channel response. With aptamer as the recognition element, a sensitive OECT‐PEC biosensor is constructed to detect the organophosphorus pesticide malathion. It is found to exhibit a good linear range, a low detection limit, and better sensitivity than the traditional PEC method.