A novel on–off PEC sensor is developed for sensitive CEA detection using WP5-functionalized Ag@Au nanowires on RGO-C₃N₄ composites.

The photoelectrochemical (PEC) platform has been a critical tool in biomolecules detection for its sensitive and selective properties. Herein, a novel signal on–off type PEC biosensing system is designed for sensitive detection of carcinoembryonic antigen (CEA) based on water-soluble pillar[5]arenes (WP5) functionalized the Ag@Au nanowires coated on reduced graphene oxide and graphitic carbon nitride composites (Ag@Au@WP5/RGO-C₃N₄). The RGO-C₃N₄ acts as a carrier for materials due to its large specific surface. Meanwhile, benefiting from the photogenerated electron-holes of RGO-C₃N₄, the local surface plasmon resonance effect of Ag@Au nanowires, the host–guest interaction of WP5 and ascorbic acid (serving as the electron donor), the fabricated PEC sensor shows favorable PEC performance for monitoring the CEA. Under optimal conditions, the detection sensitivity ranges from 0.0005 to 50 ng mL⁻¹ and the limit of detection is 0.18 pg mL⁻¹ (S/N = 3). Most importantly, the PEC sensor shows an excellent performance, satisfying human serum sample analysis. This PEC platform is expected to offer a reliable approach for early cancer diagnosis and demonstrate significant potential for clinical applications.