Ag⁺ dual-driven self-calibration for high-performance dual-photoelectrode self-powered ratiometric sensing

Despite significant advances in the dual-photoelectrode self-powered sensor, the single-signal output mode usually brings false positives/negatives from environmental interference and instrumental fluctuations, which fails to meet the requirement of accurate and sensitive detection of low-level markers in food safety and environmental monitoring. To address this critical issue, we herein report an Ag⁺ dual-driven self-calibrating strategy for self-powered ratiometric assay. In the ZnIn₂S₄//Bi₂S₃/CuTCPP dual-photoelectrode system, the synergy effect of Ag⁺-triggered DNAzyme cleavage and cation exchange on ZnIn₂S₄ photoanode produces a stable and weak reference signal. Specifically, Ag⁺-triggered DNAzyme cleavages the 3D DNA walker-amplified signal label, and the ion exchange between Ag⁺ and ZnIn₂S₄ quenches the reference signal simultaneously via electron migration pathway change. A proof-of-concept detection of mycotoxin ochratoxin A in the crop samples is demonstrated. The ratiometric self-powered sensor demonstrates a wide linear range of 10^-6 -10² ng/mL with an ultralow detection limit of 0.20 fg/mL. This work breaks the limits of single-signal self-powered detection, providing a brand-new idea for developing portable devices with great potential of on-site testing in the field environment.