Enriched Fluorescence Emission from Tungsten Disulfide Monoflake Empowered by Au Nanoexplorers

Gold nanoparticles (Au NPs) are deposited on monolayer 2D tungsten disulfide microflake (monoflake) to probe the effects of gold deposition on the physical and chemical properties of the tungsten disulfide 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 monoflake. The resultant decorated Au NPs patterns trace the concentric fluorescence pattern found on the 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 tungsten disulfide with Au NPs are sharpened and dominated by neutral excitons. This is in stark contrast to photoluminescence emission from pristine monoflake where the spectrum exhibits a multitude of emissions from trions, biexcitons, neutral excitons, and defect-bounded excitons.