High pressure surface enhanced Raman scattering spectroscopy

Fu, Yuanxi

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https://hdl.handle.net/2142/78588 Copy

Description

Title

High pressure surface enhanced Raman scattering spectroscopy

Author(s)

Fu, Yuanxi

Issue Date

2015-03-05

Director of Research (if dissertation) or Advisor (if thesis)

Dlott, Dana

Doctoral Committee Chair(s)

Dlott, Dana

Committee Member(s)

• Gruebele, Martin
• Bass, Jay D.
• Granick, Steve

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• single-molecule spectroscopy
• diamond anvil cell
• surface enhanced Raman scattering spectroscopy
• High pressure

Abstract

Surface-enhanced Raman scattering spectroscopy (SERS) was combined with the diamond anvil cell technique to study molecular monolayers and single molecules under high pressure. Vibrational spectra up to 8 GPa were obtained for self-assembled monolayers (SAMs) of the energetic material simulant 4-nitrobenzenethiol (NBT). A large pressure-broadening NO2 symmetrical stretch was found in the SAMs but not in solid NBT. Single-molecule Raman spectra were studied at high pressures (1-4 GPa). The molecules were two isotopologues of the dye rhodamine 6G (R6G and d4-R6G), adsorbed on colloidal Ag particles immobilized in polyvinyl alcohol (PVA). The distributions of pressure-induced blueshifts and linewidths of individual molecules were obtained at different pressures. The linewidth of the single-molecule Raman spectra increased little with pressure, but the variations in blueshifts increased significantly and accounted for most of the pressure-broadening found in the ensemble Raman spectra. To study the pressure effect on plasmon-based electromagnetic enhancement, localized surface plasmon resonance (LSPR) spectra of a photonic substrate and Raman scattering spectra of bezenethiol (BT) monolayers adsorbed upon were measured simultaneously under high pressure. The LSPR split into two peaks under initial compression, and both peaks redshifted with further-increased pressure. The shifts in LSPR was correlated to the Raman intensity variations found in BT Raman spectra. These results suggest that both deformation in the nanoparticles and changes in the dielectric functions with pressure should be taken into account when designing SERS substrates intended for working at high pressures.

Graduation Semester

2015-5

Type of Resource

text

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http://hdl.handle.net/2142/78588

Copyright and License Information

Copyright 2015 Yuanxi Fu

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