Spectrally Resolved Surface-Enhanced Raman Scattering Imaging Reveals Plasmon-Mediated Chemical Transformations

Challenges investigatingmolecules on plasmonic nanostructureshave limited understanding of these interactions. However, the chemicallyspecific information in the surface-enhanced Raman scattering (SERS)spectrum can identify perturbations in the adsorbed molecules to provideinsight relevant to applications in sensing, catalysis, and energyconversion. Here, we demonstrate spectrally resolved SERS imaging,to simultaneously image and collect the SERS spectra from moleculesadsorbed on individual nanoparticles. We observe intensity and frequencyfluctuations in the SERS signal on the time scale of tens of millisecondsfrom n-mercaptobenzoic acid (MBA) adsorbed to goldnanoparticles. The SERS signal fluctuations correlate with densityfunctional theory calculations of radicals generated by the interactionbetween MBA and plasmon-generated hot electrons. Applying localizationmicroscopy to the data provides a super-resolution spectrally resolvedmap that indicates the plasmonic-induced molecular charging occurson the extremities of the nanoparticles, where the localized electromagneticfield is reported to be most intense.