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Title:High pressure surface enhanced Raman scattering spectroscopy
Author(s):Fu, Yuanxi
Director of Research:Dlott, Dana
Doctoral Committee Chair(s):Dlott, Dana
Doctoral Committee Member(s):Gruebele, Martin; Bass, Jay D.; Granick, Steve
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(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.
Issue Date:2015-03-05
Rights Information:Copyright 2015 Yuanxi Fu
Date Available in IDEALS:2015-07-22
Date Deposited:May 2015

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