Polarity-Switchable Photoelectrochemical Biosensors: Applied Materials, Advances, and Mechanisms

Abstract

Photoelectrochemical (PEC) biosensors are gaining significant attention due to their high sensitivity, low background interference, and compatibility with various nanomaterials and biorecognition elements. Traditional PEC approaches, such as signal-off and signal-on methods, are effective but often hindered by background noise and limited dynamic ranges. To overcome these challenges, signal-reversal or polarity-switchable strategies have been introduced, where the direction of photocurrent changes upon target binding. While these techniques provide greater robustness, issues with stability and performance still persist. Recent advancements in photoelectrode design including semiconductor heterojunctions (such as MOF/metal oxides, MOF/metal chalcogenides, metal oxyhalides/MOFs, COFs or HOF/metal oxides), plasmonic composites (e.g., metal halides/Ag, Au/MOFs), and nanozyme-based hybrids have significantly improved light absorption, charge separation, and catalytic efficiency. Additionally, the incorporation of selective recognition elements such as molecularly imprinted polymers (MIPs), antibodies, aptamers, and enzymes enhances specificity, with analyte binding modulating photocurrents through steric effects, conformational changes, or catalytic actions. PS-PEC biosensors, which enable dynamic switching between anodic and cathodic photocurrents, offer self-calibration, enhanced resistance to environmental interference, and improved reliability. This review explores the latest advancements in PS-PEC technologies, focusing on recognition mechanisms, amplification strategies, engineered electrode materials, and detection performance.It also examines current challenges and future opportunities in biomedical diagnostics, environmental monitoring, and food safety.