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Effects of Conformational Variation on Structural Insights from Solution-Phase Surface-Enhanced Raman Spectroscopy
Mathieu L Simeral1, Aobo Zhang1, Steven M E Demers1
1Department of Physics & Astronomy, Rice University, Houston, Texas 77005-1892, United States.
The Journal of Physical Chemistry. B
|February 22, 2021
Summary
Molecular conformations significantly impact surface-enhanced Raman scattering (SERS) spectra. Time-dependent density functional theory (TDDFT) calculations reveal how molecular shape affects SERS interpretation, improving accuracy for chemical structure analysis.
Area of Science:
- Spectroscopy
- Computational Chemistry
- Materials Science
Background:
- Surface-enhanced Raman scattering (SERS) provides molecular structure information via nanoparticle electromagnetic near fields.
- Time-dependent density functional theory (TDDFT) is crucial for calculating Raman tensors for SERS interpretation.
Purpose of the Study:
- To investigate the influence of molecular conformations on SERS spectra.
- To enhance the accuracy of SERS spectral interpretation by considering molecular flexibility.
Main Methods:
- Utilized TDDFT calculations to simulate Raman spectra for various molecular conformers.
- Compared calculated spectra with experimental SERS measurements.
- Modeled lipid bilayers using TDDFT with relevant molecular conformers.
Main Results:
- TDDFT calculations with multiple conformers of cetyltrimethylammonium bromide yielded more accurate unenhanced Raman spectra than a single all-trans structure.
- Observed a loss of structural information in the CH2/CH3 scissor vibration band (1450 cm-1) in SERS spectra.
- Successfully measured the distribution of double-bond orientations in model lipid systems using conformer-based TDDFT.
Conclusions:
- Molecular conformations are critical for accurate SERS interpretation.
- TDDFT calculations considering conformers improve the understanding of molecular behavior on surfaces.
- This approach enables detailed structural analysis, such as determining double-bond orientations in complex systems like lipid bilayers.
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