Tuning the photoluminescence and ultrasensitive trace detection properties of few-layer MoS2 by decoration with gold nanoparticles

Abstract

We report an easy and inexpensive chemical route for the decoration of few-layer MoS₂ with Au nanoparticles (NPs). The Au-NPs are formed on the defect sites of the MoS₂ and localized by a non-covalent bond. The NPs act as a p-type dopant in the MoS₂ layer. An enhancement in the photoluminescence (PL) intensity of the Au–MoS₂ composite with respect to bare few-layer MoS₂ has been observed. We also systematically observed a blue shift in the excitonic emission as the number and size of the Au-NPs on MoS₂ increased. Both phenomena have been understood to result from the switching between charged exciton (trion) recombination and neutral exciton recombination. A potential application for the Au–MoS₂ composite has been demonstrated, by using it as a substrate for surface-enhanced Raman scattering (SERS). The SERS measurements show a uniform, reproducible, and strong Raman signal from the adsorbed molecules with concentrations as low as 10⁻¹² M. Our work provides a method to tune the optical and electronic properties of MoS₂, and the Au–MoS₂ composite might be useful as an efficient SERS substrate for the ultrasensitive detection of biomolecules.