Tip-Enhanced Multipolar Raman Scattering

Journal Article · Thu Apr 02 04:00:00 EDT 2020 · Journal of Physical Chemistry Letters

DOI:https://doi.org/10.1021/acs.jpclett.0c00559· OSTI ID:1630103

Wang, Chih-Feng ^[1]; Cheng, Zhihua ^[2]; O'Callahan, Brian T. ^[1]; Crampton, Kevin T. ^[1]; Jones, Matthew R. ^[2]; El-Khoury, Patrick Z. ^[1]

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1. BATTELLE (PACIFIC NW LAB)
2. Rice University

We record nanoscale chemical images of thiobenzonitrile (TBN)-functionalized plasmonic gold nanocubes via tip-enhanced Raman spectroscopy (TERS). The spatially averaged optical response is dominated by conventional (dipolar) TERS scattering from TBN but also contains weaker spectral signatures in the 1225-1500 cm-1 region. The weak optical signatures dominate some of the recorded single pixel spectra. We can uniquely assign these Raman forbidden transitions to multipolar Raman scattering, which implicates spatially varying enhanced electric field gradients at plasmonic tip-sample nanojunctions. Specifically, we can assign observations of tip-enhanced electric dipole-magnetic dipole as well as electric dipole-electric quadrupole driven transitions. These signals need to be understood and accounted for in the interpretation of TERS spectral images, particularly in on-going quests aimed at chemical reaction mapping via TERS.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1630103
• Report Number(s): PNNL-SA-151145
• Journal Information: Journal of Physical Chemistry Letters, Journal Name: Journal of Physical Chemistry Letters Journal Issue: 7 Vol. 11
• Country of Publication: United States
• Language: English