Highly sensitive PEC immunosensor for CA15–3 detection based on Bi2S3-sensitized hexagonal ZnTiO3 and Au-functionalized ZnS

The biomarker CA15–3 plays a significant role in cancer diagnosis and therapeutic monitoring. In this study, a photoelectrochemical (PEC) immunosensor was designed using hexagonal ZnTiO3/Bi2S3 heterojunction as the photoactive material, and ZnS@Au as a label for the detection antibody to amplify the signal. The hexagonal ZnTiO3 serves as the substrate material, providing a stable photocurrent response, while Bi2S3 forms a band-matching heterostructure with ZnTiO3, facilitating the transfer of photogenerated electrons. Additionally, the narrow bandgap of Bi2S3 sensitizes the material, broadening its visible light response and further enhancing the photocurrent output. Moreover, square-shaped ZnS functionalized with Au NPs is employed as a quenching signal label, which effectively competed the photogenerated electrons and consumed electron donors in the electrolyte, thereby increasing the detection sensitivity. This sensor offers a broad detection range for CA15–3, from 0.001 U·mL−1 to 1000 U·mL−1, with a detection limit of 0.0003 U·mL−1, illustrating its potential for precise and reliable cancer biomarker detection. •Simple and stable synthesis of hexagonal ZnTiO3 with application to photoelectrochemical immunoassay.•Bi2S3 sensitizes hexagonal ZnTiO3 while bandgap matching.•A special morphology of ZnS was used as a marker.•The sensor has high sensitivity and selectivity with a detection limit of 0.0003 U·mL−1.