ReS@Au NPs as signal labels quenching steady photocurrent generated by NiCoO/CdInS/InS heterojunction for sensitive detection of CYFRA 21-1.

In order to achieve rapid and sensitive detection of CYFRA 21-1, a signal-off photoelectrochemical (PEC) immunosensor was devised with NiCoO/CdInS/InS heterojunction photoactive materials as sensing platform and ReS@Au NPs as the secondary antibody labels amplifying signal based on the energy band-matching cascade structure and double suppression effect. NiCoO possessed a faster charge transfer rate due to the abundance of redox electron pairs (Co/Co and Ni/Ni). To further improve the PEC properties of NiCoO under visible light, CdInS with matching bandgap energy was selected to form heterojunction with NiCoO and sensitized with InS. The proposed heterojunctions with well-matched band structure promoted the transfer of photo-generated carriers and were exploited as signal transducers for immobilization of antibodies and recognition of CYFRA 21-1. Furthermore, a novel urchin-like p-type ReS semiconductor nanostructure functionalized by Au NPs was firstly used as a nanolabel to quench the signal. On the one hand, the Schottky heterojunction generated by ReS and Au NPs could compete with the transducer substrate for both light and electron donors. On the other hand, the large space steric hindrance of ReS prevented contact between the matrix and AA. Subsequently, the sensor was sensitive in a wide range of concentrations for CYFRA 21-1 (0.0001-50 ng/mL), and the detection limit was 0.05 pg/mL.