CdSe quantum dots support signal transduction and ratiometric detection in photoelectrochemical biosensors

Photoelectrochemical (PEC) biosensing has emerged as a powerful analytical platform by integrating photonic excitation with electrochemical detection, offering high sensitivity, low background signals, and excellent compatibility with semiconductor nanomaterials. This review systematically examines the roles of CdSe quantum dots (QDs) in advanced PEC biosensing, addressing the current lack of an integrated understanding of the relationships among their physicochemical properties, signal transduction mechanisms, and ratiometric sensing performance. Particular emphasis is placed on the interplay between electronic structure, interfacial charge transfer, surface engineering, and photocurrent generation, which collectively determine sensing efficiency and analytical reliability. Recent advances in nanocomposite engineering and biofunctional interface design are further analyzed to demonstrate their contributions to enhancing sensitivity, selectivity, and operational stability. In addition, emerging ratiometric sensing strategies are discussed as effective approaches for minimizing environmental interference and improving quantitative accuracy. Current challenges associated with surface defects, material stability, and practical implementation are also highlighted, together with future perspectives that support the rational design of next-generation CdSe QD-based PEC biosensing platforms for biomedical, environmental, and food analysis.