Correlated Super-Resolution Optical and Structural Studies of Surface-Enhanced Raman Scattering Hot Spots in Silver Colloid Aggregates

In order to advance the field of single-molecule surface-enhanced Raman scattering (SM-SERS), a better understanding of colloid morphology and hot spot properties in noble metal nanoparticle aggregates is crucial. We present super-resolution optical studies of surface-enhanced Raman scattering (SERS) from rhodamine 6G (R6G) molecules adsorbed onto silver colloid aggregates correlated with scanning electron microscope (SEM) images of those same aggregates. The scattering intensity maps of the SERS signal, obtained from the super-resolution fits, are overlaid with SEM topographical images of the colloids to map the shape of the SERS hot spot and the spatial origin of SERS intensity fluctuations with sub-5 nm resolution. These results have vital implications for developing reproducible and robust substrates capable of SM-SERS.