Portable Split-Type Photoelectrochemical Immunosensing of TBBPA via Enzymatic Amplification and Double S-Scheme Signal Transduction

Abstract Tetrabromobisphenol A (TBBPA) is an environmentally relevant brominated flame retardant that requires rapid, low-cost, and field-deployable monitoring tools, yet existing sensor-based methods remain limited by matrix interference, insufficient sensitivity, or poor compatibility with portable analysis. Here, we report a split-type photoelectrochemical (PEC) immunosensing platform that spatially separates competitive immunorecognition and glucose oxidase (GOx)-mediated H2O2 generation from PEC transduction. A double S-scheme ZnO@g-C3N4@BiOIO3 heterojunction on a screen-printed electrode serves as the H2O2-responsive photoactive interface. Band-structure analysis, light/dark XPS, open-circuit photovoltage, and charge-dynamics measurements support built-in electric field-assisted directional carrier separation across the coupled heterointerfaces, accounting for the enhanced cathodic PEC response. Target-dependent competition regulates GOx-labeled probe retention and H2O2 production, converting TBBPA concentration into attenuation of the photocurrent. The sensor exhibits a linear range of 5−5000 pM with a detection limit of 0.67 pM (0.36 ng L−1), together with good reproducibility, selectivity, and tolerance to representative matrix interferents. Direct analysis of filtered river-water samples without preconcentration yields recoveries of 91.75−110.90% relative to UPLC−MS/MS. Integration with a smartphone-compatible portable potentiostat and disposable SPE format enables low-cost field-oriented analysis. This recognition−amplification−transduction architecture provides a practical strategy for sensitive and matrix-tolerant TBBPA screening in environmental waters.