Enriched Fluorescence Emission from WS2 Monoflake Empowered by Au Nanoexplorers

Gold nanoparticles (Au NPs) are deposited on monolayer 2D tungsten disulfide (WS2) microflake (monoflake) to probe the effects of gold deposition on the physical and chemical properties of the WS2 transition metal dichalcogenides. It is found that the Au NPs behave like nanoexplorers that map out subtle and hidden chemical heterogeneity within the WS2 monoflake by way of site-selective decoration on the WS2 monoflake. The resultant decorated Au NPs patterns trace the concentric fluorescence pattern found on the WS2 monoflake. The Au NPs enhance the fluorescence intensity in selected regions within the WS2 monoflake and even activate fluorescence emission from previously dark regions. Most remarkably, the photoluminescence spectra from WS2 with Au NPs are sharpened and dominated by neutral excitons. This is in stark contrast to photoluminescence emission from pristine WS2 monoflake where the spectrum exhibits a multitude of emissions from trions, biexcitons, neutral excitons, and defect-bounded excitons.