The CdS/TiO 2 nanocomposite (NC) photoelectrochemical (PEC) sensor was constructed based on a new sensing strategy for nitrite assay. The CdS etching process caused by nitritein-acid solution was confirmed and applied to nitrite sensing. The CdS etching phenomenon occurring on the sensor led to an obvious reduction in the photocurrent response under visible-light irradiation, which responded to the nitrite concentration. The CdS/TiO 2 NCbased PEC sensor exhibited excellent performance on nitrite detection. The linear range for nitrite determination was from 1− 100 and 100−500 μM, and the sensitivity of the PEC sensor was 2.91 and 0.186 μA μM −1 cm −2 , respectively. The detection limit of the sensor was 0.56 μM (S/N = 3). In addition, the PEC sensor was also equipped with advantages such as good selectivity, excellent stability, low background, and recyclability. Satisfying results were obtained for the nitrite assay in real samples by such a PEC sensor. In summary, this work contributed a fresh idea to precisely determinate nitrite through PEC sensing.

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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.

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