Ratiometric photoelectrochemical sensors: advances in food analysis and emerging applications.

Ratiometric photoelectrochemical (PEC) sensors have emerged as a compelling class of analytical tools, offering internal calibration, enhanced signal stability, and improved tolerance to environmental variability. These advantages are particularly relevant to the field of food analysis, where sample complexity often compromises the reliability of single-signal detection strategies. In recent years, diverse ratiometric PEC platforms have been developed. This review systematically categorizes ratiometric PEC sensors into five main types: wavelength-resolved, voltage-resolved, spatially resolved, dual-mode, and other emerging strategies involving polarity switching or stimulus-responsive interfaces. For each category, representative sensing mechanisms, photoelectrode architectures, and real-world applications-especially in the detection of food contaminants such as mycotoxins, antibiotics, and pesticide residues-are comprehensively discussed. Furthermore, key challenges and future directions are outlined. This review aims to provide a conceptual foundation and technical reference for advancing ratiometric PEC sensing technologies in food safety and beyond.