Synergistic Signal Amplification by Cu ₂ O‐Au/Ag Nanozyme in Heterojunction Photoanode for High‐Sensitivity Photoelectrochemical Detection of Cyfra21‐1

Abstract Sensitive photoelectrochemical (PEC) analysis relies on high‐efficiency signaling strategies. Here, a hollow Cu ₂ O‐Au/Ag nanozyme is developed to realize synergetic signal amplification on a MoS ₂ @ZnIn ₂ S ₄ heterojunction‐based PEC platform for Cyfra21‐1 detection. The MoS ₂ @ZnIn ₂ S ₄ photoelectrode exhibited excellent photoactivity due to the formation of directional built‐in electric fields, providing an additional driving force to enhance the rapid transfer of photo‐induced electrons. To further improve the sensitivity of the immunosensor, a multifunctional Cu ₂ O‐Au/Ag nanozyme probe is designed. It amplifies the photocurrent signal through three different mechanisms: the intrinsic enzyme‐like activity of the probe, the localized surface plasmon resonance effect from Au/Ag nanoparticles, and the p‐type Cu ₂ O‐driven coreactant scavenging. These properties work synergistically to enable catalytic deposition amplification, competitive light absorption, and coreactant consumption with photoactive substrate, ultimately leading to significant improvement in sensor performance. The proposed platform demonstrated high sensitivity (0.0360 pg mL ⁻¹ ), a broad linear range (0.100 pg mL ⁻¹ to 50.0 ng mL ⁻¹ ), as well as satisfactory stability and repeatability. This study presents an effective signaling strategy for achieving sensitive bioanalysis through nanozyme‐induced synergistic signal amplification.