Synergistically enhanced ternary Schottky/S-scheme homojunction for ultrasensitive photoelectrochemical sensing

Abstract 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.