Currently, constructing heterojunctions to improve photoelectric conversion efficiency represents a highly promising approach for improving the sensitivity in photoelectrochemical (PEC) sensors. Nevertheless, the performance enhancement is often constrained by the lattice mismatch between dissimilar semiconductors. In this work, we introduce a novel synergistic enhancement model based on a Schottky-coupled S-scheme homojunction. By controlling different conditions under the same hydrothermal method, the homojunction of CdS quantum dots grown in-situ on CdS nanorods was synthesized. The homojunction features intimate interfacial contact, a perfectly matched lattice, and an S-scheme carrier pathway, thus increasing the photocurrent response by 17 times. Subsequent integration with gold nanoparticles further amplifies the performance, yielding a synergistic 31-fold improvement. Leveraging this architecture, we demonstrate an ultrasensitive PEC biosensor for the detection of C-reactive protein activity, operating at 0 V bias and without sacrificial agents. This pioneering strategy of combining Schottky junctions with S-scheme homojunctions offers a new direction for advancing photoelectric performance in PEC sensing.

Immobilizing enzymes within metal-organic frameworks (MOFs) enables enzymes to against extreme environments. However, these MOF shells are just like armors, protective but heavy, which shield the enzymes from threats while locking them in the cage. The exploitation of immobilization strategy and intrinsic property of MOFs themselves is of great significance. Here, we proposed a functional protein trap strategy for efficient enzyme encapsulation. The ferrocenedicarboxylic acid (Fc) was used to induce the formation of defect-rich Co-based MOFs (CoBDC-Fc). As result, the engineered protein trap can not only improve the enzyme loading but also accelerate catalytic efficiency. Specifically, the atomically dispersed Fc sites serve as cocatalysts/cofactors and even change the conformation of enzymes in the construed microenvironment. Furthermore, the obtained CoBDC-Fc/enzyme exhibits excellent recyclability and tolerance to inhospitable conditions. Benefited by these, the CoBDC-Fc/enzyme/antigen composites were further prepared for cascade enzyme-linked immunosorbent assay of prostate-specific antigen with satisfactory sensitivity.