Nanocomposite Hydrogel Enables Color‐Gated Organic Photoelectrochemical Transistor Biodetection

Abstract The newly emerged organic photoelectrochemical transistor (OPECT) has been demonstrated promising in diverse sectors, yet its underlying operation rationale remains largely unexplored due to its short development time. Color, arising from the light‐matter interactions, is ubiquitous in nature. Here the concept of color‐gated OPECT biodetection based on a nanocomposite hydrogel is proposed and devised, which is exemplified by the automatic color change of Pt nanocubes (NCs)‐encapsulated hydrogel with Ag + ‐responsiveness. Linking with a sandwich immunorecognition with labeled silver nanoparticles (Ag NPs), chemical etching‐released Ag + can sensitively affect the Pt NCs‐catalyzed conversion of o‐phenylenediamine, leading to the color change of the nanocomposite hydrogel and thus the altered gating characteristics. This study features the concept of color‐gated OPECT biodetection and is expected to catalyze a new category of advanced “colored” optobioelectronics, given the rich color change from the light‐matter‐bio interactions.