Near-infrared-responsive photoelectrochemical biosensors

Biomarker identification is critical for noninvasive early disease diagnosis, addressing limitations found in traditional methods such as ELISA. As an alternative, photoelectrochemistry (PEC) has been extensively explored due to its cost-effectiveness and rapid response times. PEC in the near-infrared (NIR) region is particularly promising, offering high sensitivity, minimal background signal, and biocompatibility, which are essential for minimizing potential tissue damage. This review probes into recent advancements in NIR-responsive PEC biosensors, emphasizing photoactive species, charge transfer mechanisms, and other critical aspects. It categorizes NIR-PEC systems into three primary types: (i) photonic indirect materials utilizing upconversion nanomaterials and their composites; (ii) photonic direct materials employing plasmonic nanomaterials, photonic crystals, narrow-bandgap semiconductors, and their heterojunctions; and (iii) nanophotonic photothermal materials driven by pyroelectric effects and involving their heterojunctions. Additionally, the review introduces biological recognition elements used in NIR-PEC biosensors, classifying them into "signal-on", "signal-off" and "signal- reversal" types. This comprehensive examination provides a general understanding of the evolving NIR-PEC landscape, offering valuable insights into its potential for portable, on-site, point-of-care, and clinical applications in disease diagnosis.