Metal-organic frameworks-based hierarchical heterojunction coupling with plasmonic nanoshells for self-powered photoelectrochemical immunoassay

Benefiting from the large specific areas and versatile designability, metal–organic frameworks (MOFs) based materials open a new avenue for the design of superior catalysts, whereas their applications in sensitive detection are still in their infancy. Herein, plasmon-promoted MOFs-based photoelectrochemical (PEC) immunoassays with hierarchical structures (AgAu/[email protected]@CdS) are prepared via a MOFs-engaged directional deposition method and ion-exchange reaction. As a result, the hierarchical structures exhibit excellent PEC performance with reinforced light absorption and charge separation efficiency. Reaction dynamics at the electron level and spatial-resolved simulations clarify that the multi-heterostructure interfaces of [email protected]@CdS and the plasmonic effect of AgAu nanoshells can synergistically improve the light absorption efficiency and promote the spatial separation of the electron-hole pairs. Notably, the MOFs shells are found to dramatically enhance the electromagnetic field and prevent the decay along the radial direction, which is favorable to the charge separation and transfer. Taking prostate-specific antigen as a representative analyte, both label-free and sandwich-type self-powered immunoassays exhibit superior detection performance with limits of detection (LODs) as low as 0.11 pg·mL−1 and 0.9 fg·mL−1, respectively. This study offers a promising platform for the construction of ultrasensitive immunoassays and provides methodologies for the mechanism investigation beyond the PEC detection performance.