Self-supporting BiVO4@UiO-66-CdS QD hierarchical scaffold-based heterojunction band alignment for synergistic gain optoelectronic organic transistor sensing.

While band alignment engineering will facilitate charge separation and channel current modulation in heterojunctions, its application in organic photoelectrochemical transistors (OPECT) is hindered by a limited understanding of interfacial photogating dynamics. To address this limitation, we engineered a chemically reconfigurable heterojunction photogate, denoted as BiVO4@UiO-66-CdS QD, which consists of electrospun BiVO4 nanofibers combined with a porous UiO-66(Zr) framework loaded with CdS QD. The zero-bias band alignment and charge-transfer route in the BiVO4@UiO-66-CdS QD heterojunction were investigated using H2O2 as a photoelectronic modulator. Through H2O2-triggered valence changes and in situ band reconstruction, we achieved dynamic reversal of photocurrent polarity and switching of dominant photogenerated species from ∙O2- to ∙OH. We demonstrated this concept by applying the built-in H2O2 response to detecting formamidopyrimidine-DNA glycosylase (FPG) at the heterostructure-based OPECT photogate. A target-triggered rolling circle amplification strategy was used to produce long DNA scaffolds for immobilizing glucose oxidase. Enzymatically produced H2O2 causes oxidative modifications to the UiO-66-CdS QD interface, dynamically altering its band structure and increasing the transistor channel current. The freestanding heterojunction allows for dense and aggregation-free attachment of CdS QD, providing a plentiful supply of photogenerated electrons. By merging enhanced photoconductive gain with H2O2 responsive dynamic band modulation, the developed OPECT biosensor demonstrates outstanding sensitivity for FPG, with a detection limit of 2.79 × 10-6 U·μL-1 and a wide linear range from 10-5 to 1 U·μL-1. This study shows that moving from static heterojunctions to dynamically tunable interfaces opens the door to a new generation of adaptive, high-performance OPECT biosensors.