ReS2@Au NPs as signal labels quenching steady photocurrent generated by NiCo2O4/CdIn2S4/In2S3 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 NiCo 2 O 4 /CdIn 2 S 4 /In 2 S 3 heterojunction photoactive materials as sensing platform and ReS 2 @Au NPs as the secondary antibody labels amplifying signal based on the energy band-matching cascade structure and double suppression effect. NiCo 2 O 4 possessed a faster charge transfer rate due to the abundance of redox electron pairs (Co3+/Co2+ and Ni3+/Ni2+). To further improve the PEC properties of NiCo 2 O 4 under visible light, CdIn 2 S 4 with matching bandgap energy was selected to form heterojunction with NiCo 2 O 4 and sensitized with In 2 S 3. 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 2 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 2 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 2 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. [ABSTRACT FROM AUTHOR]