Breaking the Dual-Interface Limitation: A Magnetically Controlled Ratiometric Photoelectrochemical Sensor Using Lattice-Strained BiOBr and a Ferrocyanide–Ascorbic Acid Hybrid Electrolyte

Ratiometric photoelectrochemical (PEC) sensors often require complex designs involving dual-modified photoelectrode interfaces or specific excitation-wavelength materials, which limit their practical utility. This study proposed a highly universal strategy for ratiometric PEC sensors based on magnetic field regulation, allowing for the detection of two signals via a single interface. Specifically, the PEC activity of the magnetic secondary antibody label ZnFe₂O₄@TiO₂ could be modulated by an external magnetic field, which achieved dual-signal output and ratiometric detection. By eliminating dual-interface modifications, signal output inconsistencies were reduced, while the magnetic control mechanism made ratiometric detection no longer need material redesign. Furthermore, the sensing platform employed strain-engineered BiOBr nanosheets decorated with Bi₂S₃ nanoparticles (StBiOBr-s) to optimize charge separation. Coupled with a K₄[Fe(CN)₆]/ascorbic acid hybrid electrolyte, this design significantly accelerated interfacial electron transfer. Such synergistic material and electrolyte engineering provided a generalizable framework for high-performance PEC systems. The sensor system exhibited high sensitivity for neuron-specific enolase with a 30 fg/mL limit of detection, demonstrating both the practical utility for biomarker analysis and the broader potential of this approach for PEC sensing applications.