High-gain signal-on PEDOT:PSS organic photoelectrochemical transistor biosensing modulated by a MXene/MOFs/NiO Schottky heterojunction

Herein we report a high-gain signal-on poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) organic electrochemical transistor (OECT) biosensing using an accumulation-mode PEDOT:PSS OECT modulated by a light-fueled MXene/MOFs/NiO Schottky heterojunction. In such a system, the MXene/MOFs/NiO Schottky heterojunction exhibited superior gating effect, as it not only enabled the fast-directional charge transfer but also guaranteed the maximal accessibility of the electrolyte to topped 2D MXene with large surface area. In linkage with a bi-enzyme cascade system, the quinone derivatives produced by the cascade reaction of alkaline phosphatase (ALP) and tyrosinase (TYR) could serve as effective electron acceptors for the representative Ti3C2/PCN-224/NiO heterojunction, underpinning an innovative method for sensitive detection of ALP activity with a low detection limit of 0.001 U L−1. Remarkably, the as-developed system demonstrated a remarkable current gain as high as near 104, which to our knowledge is the highest one among existing OECT biosensory devices. This work represents a generic protocol to develop the novel signal-on PEDOT:PSS OECT platform towards biochemical detection and beyond.