Single-molecule surface-enhanced raman scattering: Can STEM/EELS image electromagnetic hot spots?

Nasrin Mirsaleh-Kohan, Vighter Iberi, Philip D. Simmons, Nicholas W. Bigelow, Alex Vaschillo, Meng M. Rowland, Michael D. Best, Stephen J. Pennycook, David J. Masiello, Beth S. Guiton, Jon P. Camden

Research output: Contribution to journalArticlepeer-review

60 Scopus citations


Since the observation of single-molecule surface-enhanced Raman scattering (SMSERS) in 1997, questions regarding the nature of the electromagnetic hot spots responsible for such observations still persist. For the first time, we employ electron-energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) to obtain maps of the localized surface plasmon modes of SMSERS-active nanostructures, which are resolved in both space and energy. Single-molecule character is confirmed by the bianalyte approach using two isotopologues of Rhodamine 6G. Surprisingly, the STEM/EELS plasmon maps do not show any direct signature of an electromagnetic hot spot in the gaps between the nanoparticles. The origins of this observation are explored using a fully three-dimensional electrodynamics simulation of both the electron-energy-loss probability and the near-electric field enhancements. The calculations suggest that electron beam excitation of the hot spot is possible, but only when the electron beam is located outside of the junction region.

Original languageEnglish
Pages (from-to)2303-2309
Number of pages7
JournalJournal of Physical Chemistry Letters
Issue number16
StatePublished - Aug 16 2012

ASJC Scopus subject areas

  • Materials Science (all)
  • Physical and Theoretical Chemistry


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