Surface-Bulk Correlation Spectroscopy for the Characterization of Ternary Adsorption.
Mahsa Torkamanasadi1, Dennis K Hore1,2
1Department of Chemistry, University of Victoria, Victoria, British Columbia, V8W 3V6, Canada.
Applied Spectroscopy
|June 30, 2025
Summary
A new method quantifies molecular adsorption on surfaces by analyzing bulk and surface spectra. This reveals how different molecules compete for surface binding, aiding in understanding surface preference in mixtures.
Area of Science:
- Surface science
- Spectroscopy
- Physical chemistry
Background:
- Understanding molecular adsorption on solid substrates is crucial for various applications, including catalysis and materials science.
- Characterizing the behavior of ternary mixtures (three-component systems) presents unique challenges due to complex interactions.
- Quantifying equilibrium constants and surface preferences in multi-component adsorption is often difficult with traditional methods.
Purpose of the Study:
- To propose a novel method for determining the range of equilibrium constants for ternary mixtures adsorbed onto solid substrates.
- To establish a link between adsorption equilibrium constants and the surface preference of individual molecular species.
- To provide a systematic approach for analyzing multi-component adsorption phenomena.
Main Methods:
- Utilizes heterospectral two-dimensional correlation analysis combining infrared (IR) and/or Raman spectroscopy of the bulk phase with sum frequency generation (SFG) spectroscopy of the surface.
- Involves a series of experiments (up to three) where bulk concentrations of the mixture components are systematically varied.
- Employs a defined set of rules for interpreting the resulting correlation maps to identify adsorption sequences and determine surface preference.
Main Results:
- The proposed method successfully obtains the range of equilibrium constants describing ternary mixture adsorption.
- The analysis of correlation maps allows for the identification of adsorption sequences and the determination of relative surface preferences.
- A clear relationship between spectral data and adsorption behavior is established.
Conclusions:
- The developed heterospectral correlation analysis provides a robust method for studying multi-component adsorption.
- This technique enables the quantitative assessment of surface preference in complex molecular mixtures.
- The study offers a scheme to guide experimental design and data interpretation for ternary adsorption systems.
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