Shell Thickness Dependence of the Plasmon-Induced Hot-Electron Injection Process in Au@CdS Core–Shell Nanocrystals

The shell thickness dependence of the ultrafast plasmon-induced hot-electron injection process in Au@CdS core–shell nanocrystals has been studied with mid-infrared and visible femtosecond transient absorption spectroscopies. As the thickness of the CdS shell increases, we observe that the hot-electron injection efficiency initially increases but then decreases after a critical point (at around 8–10 nm), which is consistent with the trend for the shell thickness-dependent photocatalytic hydrogen evolution. Combined with the theoretical calculation, we find that the electron injection efficiency is mainly determined by two decisive factors, which are the initial hot-electron energy distribution in the Au core after Landau damping and the Schottky potential in the interface of the Au core and the CdS shell. This finding offers a practical and effective approach to optimize the photocatalytic efficiency of a metal–semiconductor heterostructure by tuning its structure.