Spin-Selective Charge Modulation in a Chiral Topological Heterojunction for Ultrasensitive Photoelectrochemical Detection of Polyvinyl Chloride

Efficient suppression of carrier recombination is crucial for enhancing the performance of photoelectrochemical (PEC) biosensors. Here, we engineered a chiral molecule-modified BiOI/ZIF-8 (BZ) heterojunction in which the carrier separation efficiency of the paper-based photoactive chip is precisely regulated through manipulation of interfacial spin states and the rational construction of electron-transport pathways. The chirality-induced spin selectivity effect of the chiral molecule forces photogenerated electrons into a parallel spin configuration, thereby blocking spin-allowed electron-hole recombination and prolonging carrier lifetimes. Magnetic conductive atomic force microscopy measurements further confirm that the chiral topology induces a pronounced spin polarization of up to 70.8% at room temperature. As a proof-of-concept application, a paper-based spin tunable photoelectrochemical (μ-PEC) sensor was developed based on a competitive binding strategy for highly sensitive and selective onsite detection of poly(vinyl chloride) (PVC), with a detection limit of 1.32 ng/mL. This study demonstrates that the tunability of the spin degree of freedom provides a powerful avenue for transcending the inherent limitations of conventional photoactive materials, opening up promising avenues for environmental monitoring, spin-regulated optoelectronics, and next-generation photoelectrochemical sensing platforms.