Evaluating Single-Molecule Stokes and Anti-Stokes SERS for Nanoscale Thermometry

Eric A. Pozzi, Alyssa B. Zrimsek, Clotilde M. Lethiec, George C Schatz, Mark C Hersam, Richard P. Van Duyne

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

Plasmonic near fields, wherein light is magnified and focused within nanoscale volumes, are utilized in a broad array of technologies including optoelectronics, catalysis, and sensing. Within these nanoscale cavities, increases in temperature are expected and indeed have been demonstrated. Heat generation can be beneficial or detrimental for a given system or technique, but in either case it is useful to have knowledge of local temperatures. Surface-enhanced Raman spectroscopy (SERS), potentially down to the limit of single-molecule (SM) detection, has been suggested as a viable route for measuring nanoscale temperatures through simultaneous collection of Stokes and anti-Stokes SER scattering, as the ratio of their intensities is related to the Boltzmann distribution. We have rigorously verified SM detection in anti-Stokes SERS of rhodamine 6G on aggregated Ag nanoparticles using the isotopologue method. We observe a broad distribution in the ratio of anti-Stokes and Stokes signal intensities among SM events. An equivalent distribution in high-coverage, single-aggregate SERS suggests that the observed variance is not a SM phenomenon. We find that the variance is instead caused by a combination of local heating differences among hot spots as well as variations in the near-field strength as a function of frequency, effectively causing nonequivalent enhancement factors (EFs) for anti-Stokes and Stokes scattering. Additionally, we demonstrate that dark-field scattering cannot account for the frequency dependence of the optical near field. Finite-difference time-domain simulations for nanoparticle aggregates predict a significant wavelength dependence to the ratio of anti-Stokes/Stokes EFs, confirming that the observed variation in this ratio has strong nonthermal contributions. Finally, we outline the considerations that must be addressed in order to accurately evaluate local temperatures using SERS.

Original languageEnglish
Pages (from-to)21116-21124
Number of pages9
JournalJournal of Physical Chemistry C
Volume119
Issue number36
DOIs
Publication statusPublished - Sep 10 2015

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temperature measurement
Raman spectroscopy
near fields
Molecules
Scattering
molecules
scattering
Nanoparticles
nanoparticles
Temperature
Boltzmann distribution
augmentation
heat generation
Heat generation
rhodamine
Optoelectronic devices
Catalysis
surface temperature
catalysis
temperature

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

Cite this

Evaluating Single-Molecule Stokes and Anti-Stokes SERS for Nanoscale Thermometry. / Pozzi, Eric A.; Zrimsek, Alyssa B.; Lethiec, Clotilde M.; Schatz, George C; Hersam, Mark C; Van Duyne, Richard P.

In: Journal of Physical Chemistry C, Vol. 119, No. 36, 10.09.2015, p. 21116-21124.

Research output: Contribution to journalArticle

Pozzi, Eric A. ; Zrimsek, Alyssa B. ; Lethiec, Clotilde M. ; Schatz, George C ; Hersam, Mark C ; Van Duyne, Richard P. / Evaluating Single-Molecule Stokes and Anti-Stokes SERS for Nanoscale Thermometry. In: Journal of Physical Chemistry C. 2015 ; Vol. 119, No. 36. pp. 21116-21124.
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