Classical Model of Surface Enhanced Infrared Absorption (SEIRA) Spectroscopy

Area of Science:

• Plasmonics
• Spectroscopy
• Materials Science

Background:

• Molecule-plasmon interactions underpin surface-enhanced infrared absorption (SEIRA) and surface-enhanced Raman scattering (SERS).
• Classical electromagnetic theory provides a framework for understanding these interactions when molecular transition moments are properly described.
• Previous work established a classical model for Raman excitation profiles.

Purpose of the Study:

• To generalize the understanding of plasmon-molecule interactions by investigating the SEIRA signal of N2O on a Dy-doped CdO (CdO:Dy) film.
• To explore the use of semiconductor materials with tunable plasmon dispersion for enhanced vibrational spectroscopy.
• To validate a classical model predicting SEIRA phase behavior and enhancement factors.

Main Methods:

• Utilized a Dy-doped CdO (CdO:Dy) film with tunable near- and mid-infrared plasmon dispersion.
• Employed the Kretschmann configuration with CaF2 prism and MgO substrate for SEIRA measurements.
• Developed and applied a classical model to predict SEIRA signals and enhancement factors.

Main Results:

• The CdO:Dy film demonstrated tunable plasmon dispersion interacting with vibrational transitions.
• The classical model successfully predicted the phase behavior of SEIRA.
• A calculated SEIRA enhancement factor of 6.2 was achieved, closely matching the experimental value of 6.8 ± 0.5 relative to an Au control.

Conclusions:

• Dy-doped CdO is a promising material for SEIRA and SERS applications due to its tunable plasmonics.
• The classical electromagnetic model effectively describes molecule-plasmon interactions in SEIRA.
• This work advances the understanding and application of plasmon-enhanced vibrational spectroscopies.