Interface-engineered Au@MoS2 core-shell heterostructures with superior hot-carrier transfer dynamics for plasmonics and optoelectronics

Heterostructures constructed by noble metals and two-dimensional (2D) semiconductors offer a unique charge transport path to collect hot carriers from plasmonic nanostructures and thus are promising for various plasmonic and optoelectronic devices. However, the desired charge transfer speed and efficiency of the conventional heterostructures are usually restricted by the limited interface area and inevitable interface distortion and contamination. Herein, we report the ultrafast and high-efficiency hot electron transfer by creating a novel Au@MoS2 core-shell heterostructure with atomically sharp and dramatically enlarged interface. Our femtosecond transient absorption spectroscopy study indicates the hot-electron injection from Au nanoparticles to MoS2 in Au@MoS2 is within 244 fs, compared with the 493 fs of the mechanically-transferred Au/MoS2 control sample. And meanwhile, the injection efficiency is improved from 3.33% of Au/MoS2 to 25.3% of our Au@MoS2. The results are further proved by Kelvin probe force microscopy and discrete dipolar approximation studies, which provide strong evidences that the improved charge transfer is attributed to the atomic-level clean and fully-encapsulated interface of the product. This study provides fundamental understanding of the intrinsic charge transfer within Au@MoS2 heterostructures and thus demonstrates an intriguing material geometry for future plasmonic and optoelectronic devices.