Elaborate Design of Zn x Cd 1‐x In 2 S 4 and Cu 2 O@Mn 3 Cu 3 O 8 Based on Doping Engineering with Amplified Current Changes for Convenient Colorimetric and Efficient Organic Photoelectrochemical Transistor Dual‐Mode Biosensing

Abstract The organic photoelectrochemical transistor (OPECT) has emerged as a novel and promising platform for the direction of bioelectronics and optoelectronics. Nevertheless, significant challenges and hurdles remain exiting in achieving higher gating efficiency and more sensitive biosensing performance, which are mainly caused by the recombination of photo‐generated carriers on the photogate and the limited strategy of inherent signal amplification. Inspired by the doping engineering and multi‐mode biosensors, an elaborate design of Zn x Cd 1‐x In 2 S 4 and Cu 2 O@Mn 3 Cu 3 O 8 (CMCO) based on doping engineering is reported, and combined with the catalytic hairpin assembly (CHA) cascade biomimetic precipitation, realizing the dual‐mode biosensing of colorimetric and OPECT system. Specifically, a large amount of target‐dependent CMCO loaded on the photogate via CHA can convert the 3,3′,5,5′‐tetramethylbenzidine (TMB) into oxTMB for convenient visualization. On the other hand, the generation of biomimetic precipitation can result in a significant spatial site‐blocking effect for efficient OPECT biosensing. The biosensing device exhibits a linear range from 0.1 to 10 4 p M with a detection limit of 48 fM in visual mode, and exhibits a satisfactory linear range from 0.5 f M to 100 p M with a detection limit of 0.11 f M in OPECT mode, demonstrating a high accuracy and sensitivity for novel dual‐mode bioanalytics.