Visualizing the bidirectional electron transfer in a Schottky junction consisting of single CdS nanoparticles and a planar gold film

Bidirectional electron transfer crossing the metal/semiconductor interface regulates the light absorption and carrier separation efficiency of plasmonic-semiconductor hybrid nanomaterials. Existing studies have been largely focused on a localized surface plasmon resonance (LSPR) effect contributed by an ensemble of metal nanomaterials. Herein, we constructed a Schottky junction that consisted of single CdS nanoparticles and a planar gold film, and investigated hot electrons excited by the surface plasmon polaritons (SPPs) propagating in the gold film. When illuminating the interface with blue light, photoinduced electrons were found to inject from the CdS nanoparticle to the gold film. In a reverse process, SPPs were generated on shining a red beam into the gold film via a Kretschmann configuration, resulting in the injection of hot electrons into CdS nanoparticles. A recently developed plasmonic microscopy method was employed to monitor the entire process, providing the ability to image a single nanoparticle to visualize the bidirectional electron transfer dynamics in a Schottky junction involving propagating SPPs. The present study advances the understanding of the mechanism of hot electron transfer, which is anticipated to aid in the rational design and optimization of plasmonic-semiconductor hybrid nanomaterials with broad applications in photocatalysis, photovoltaic devices, and photoelectrochemical sensing.