Upconversion NaYF₄:Yb/Er-TiO₂-Ti₃C₂ Heterostructure-Based Near-Infrared Light-Driven Photoelectrochemical Biosensor...

A near-infrared (NIR) light-driven NaYF₄:Yb/Er-TiO₂-Ti₃C₂ (NYF-TiO₂-Ti₃C₂) heterostructure-based photoelectrochemical (PEC) biosensing platform was constructed for highly sensitive d-serine (d-ser) detection. Accurate d-ser detection depends on the model biocatalyst, d-amino acid oxidase (DAAO), which converts d-ser into hydroxypyruvate and an equimolar concentration of hydrogen peroxide (H₂O₂) via an enzymatic reaction. The TiO₂-Ti₃C₂ semiconductor and NaYF₄:Yb/Er optical transducer formed a Schottky junction that provided an irreversible channel for electron transfer. Infrared light was converted into absorbable multiemission light, thereby effectively increasing light absorption. Simultaneously, the generated H₂O₂ rapidly scavenged photogenerated holes to separate electron-hole pairs, which amplified the photocurrent signal. Under optimal conditions, the NIR light-driven PEC biosensor exhibited an excellent PEC performance for d-ser detection, with a wide linear range of 2-1650 μmol L^-1 and detection limit as low as 0.286 μmol L^-1. Importantly, high detection reproducibility and accuracy were achieved using this strategy for analyzing human serum and rat cerebrospinal fluid (CSF) specimens. The admirable applicability of the NYF-TiO₂-Ti₃C₂-based PEC biosensor for detecting d-ser may lead to further opportunities for detecting other disease-related biomarkers.