title: Super-resolution imaging reveals a difference between SERS and luminescence centroids.
abstract: Super-resolution optical imaging of Rhodamine 6G surface-enhanced Raman scattering (SERS) and silver luminescence from colloidal silver aggregates are measured with sub-5 nm resolution and found to originate from distinct spatial locations on the nanoparticle surface. Using correlated scanning electron microscopy, the spatial origins of the two signals are mapped onto the nanoparticle structure, revealing that, while both types of emission are plasmon-mediated, SERS is a highly local effect, probing only a single junction in a nanoparticle aggregate, whereas luminescence probes all collective plasmon modes within the nanostructure. Calculations using the discrete-dipole approximation to calculate the weighted centroid position of both the |E|(2)/|E(inc)|(2) and |E|(4)/|E(inc)|(4) electromagnetic fields were compared to the super-resolution centroid positions of the SERS and luminescence data and found to agree with the proposed plasmon dependence of the two emission signals. These results are significant to the field of SERS because they allow us to assign the exact nanoparticle junction responsible for single-molecule SERS emission in higher order aggregates and also provide insight into how SERS is coupled into the plasmon modes of the underlying nanostructure, which is important for developing new theoretical models to describe SERS emission.
authors.affiliation: Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States.
authors.forename: Maggie L
authors.initials: ML
authors.lastname: Weber
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Litz
authors.forename: David J
authors.initials: DJ
authors.lastname: Masiello
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Willets
mesh_terms: D008163:Luminescent Measurements; D053768:Metal Nanoparticles / Q000737:chemistry; D012235:Rhodamines / Q000737:chemistry; D012834:Silver / Q000737:chemistry; D012965:Sodium Chloride / Q000737:chemistry; D013059:Spectrum Analysis, Raman; D013499:Surface Properties
chemical_list: D012235:Rhodamines; C026188:rhodamine 6G; D012834:Silver; D012965:Sodium Chloride