TY - JOUR
T1 - Single-molecule surface-enhanced raman scattering
T2 - Can STEM/EELS image electromagnetic hot spots?
AU - Mirsaleh-Kohan, Nasrin
AU - Iberi, Vighter
AU - Simmons, Philip D.
AU - Bigelow, Nicholas W.
AU - Vaschillo, Alex
AU - Rowland, Meng M.
AU - Best, Michael D.
AU - Pennycook, Stephen J.
AU - Masiello, David J.
AU - Guiton, Beth S.
AU - Camden, Jon P.
PY - 2012/8/16
Y1 - 2012/8/16
N2 - 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.
AB - 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.
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U2 - 10.1021/jz300967q
DO - 10.1021/jz300967q
M3 - Article
AN - SCOPUS:84865067916
VL - 3
SP - 2303
EP - 2309
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
IS - 16
ER -