Plasmon-Induced Energy Transfer and Photoluminescence Manipulation in MoS2 with a Different Number of Layers

Monolayer or few-layer molybdenum disulfide (MoS2) with intriguing physical properties enables a wide range of applications such as photocatalysis and photodetection. The controllable light–matter interaction in MoS2 nanoflakes with different numbers of layers is critical for developing new optoelectronic functionalities. Recently, plasmonic nanostructures have been used to obtain strong near-field enhancement for the effective photoluminescence (PL) manipulation of MoS2. However, it is still unclear whether the PL manipulation is dominated by electron injection processes or the strong field induced Purcell effect so far. Here, we investigate the PL manipulation of MoS2 nanoflakes with different numbers of layers using Au nanoparticles with different aggregate states. Combining the measured PL and scattering spectra, the Kelvin probe force microscopy images at the single-particle level, and the numerical simulations, we figure out how the electron injection and strong field enhancement contribute to the PL manipulation and why PL quenching occurs in few-layer flakes but PL enhancement occurs in thicker flakes. These findings would give us a greater understanding of the interaction between two-dimensional materials and plasmonic nanostructures.