Hollow performances quenching label of Au NPs@CoSnO₃ nanoboxes-based sandwich photoelectrochemical immunosensor for sensitive CYFRA 21-1 detection

In this work, a fire-new “signal-off” type photoelectrochemical (PEC) immunosensor based on bismuth sulfide/iodine doped bismuth oxychloride (Bi₂S₃/I:BiOCl) heterostructure as a platform and Au nanoparticles loaded hollow CoSnO₃ nanoboxes (Au NPs@CoSnO₃) as quenching label was designed, for sensitive detection of CYFRA 21-1. The I:BiOCl with flower-like structure could supply high specific surface area for loading nanometer materials. Then, Bi₂S₃ was formed in-situ by S²⁻ adsorption on the surface of I:BiOCl by dangling bond of Bi³⁺, but did not change the flower-like structure of I:BiOCl. Then, n-type Bi₂S₃ and p-type I:BiOCl heterostructure showed good photoelectric behavior by providing an additional electric field to accelerate electron-hole separation. Furthermore, the production process of the heterostructure was simple, fast, low temperature, and without complex raw materials. The Au NPs@CoSnO₃ with good photocatalytic activity could strongly compete with Bi₂S₃/I:BiOCl for electron donor of ascorbic acid (AA). Meanwhile, the CoSnO₃ with hollow structure made the quenching effect more significant by the light-scattering effect that enhanced the light absorption capacity and shorten distance of carrier transport. Under optimal conditions, this proposed strategy displayed the low detection limit of 30 fg/mL, with a high linearity range from 100 fg/mL to 100 ng/mL for tumor markers CYFRA 21-1. Simultaneously, it also exhibited excellent specificity and acceptable stability, which might provide a new perspective for the fabrication of other PEC immunosensors with heterostructure simple synthesis and hollow materials.