A dual-quenched photoelectrochemical immunosensor based on a CdS/SrTiO₃ heterojunction for CA12-5 sensitive detection

The early diagnosis and postoperative monitoring of ovarian cancer rely significantly on the sensitive detection of antigen CA12-5. In this work, a photoelectrochemical immunosensor was developed for the detection of CA12-5, utilizing a CdS/SrTiO₃ heterojunction as the photoactive matrix and NiCo₂O₄ as a quencher probe. The Z-type heterojunction promotes the separation of photogenerated electrons and holes, suppresses the recombination of charge carriers, and thereby significantly enhances the initial photocurrent response. Furthermore, the introduced NiCo₂O₄ quencher generates steric hindrance and competes effectively with the photosensitive material for light absorption, leading to a reduction in the photocurrent signal. This quenching effect greatly enhances the detection sensitivity for CA12-5. The fabricated immunosensor exhibited excellent selectivity and stability under optimal conditions, achieving a wide linear detection range from 5 pg mL^-1 to 50 ng mL^-1 and a low detection limit of 1.3 pg mL^-1.