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Charge Separation Dynamics of Aromatic Molecules at Aqueous Interfaces Revealed by Ultrafast Photoelectron
Yo-Ichi Yamamoto1, Toshinori Suzuki1
1Department of Chemistry, Graduate School of Science, Kyoto University Kyoto 606-8502, Japan.
Journal of the American Chemical Society
|December 31, 2025
Summary
Investigating interfacial reactions using extreme ultraviolet time-resolved photoelectron spectroscopy (EUV-TRPES), this study reveals altered reaction dynamics for surface-active molecules like indole and phenol at the air-water interface. These findings enhance our understanding of interfacial chemistry.
Area of Science:
- Physical Chemistry
- Surface Science
- Spectroscopy
Background:
- Molecules at the air-water interface exhibit higher concentrations and potentially altered reaction rates compared to bulk solutions.
- The influence of the interfacial solvation environment on intrinsic reaction rate constants remains poorly understood.
Purpose of the Study:
- To investigate the photoinduced charge-separation dynamics of surface-active organic molecules (indole, phenol, phenolate) at the air-water interface.
- To determine if interfacial solvation environments intrinsically alter reaction rate constants.
- To demonstrate the capability of extreme ultraviolet time-resolved photoelectron spectroscopy (EUV-TRPES) for probing interfacial dynamics.
Main Methods:
- Utilized extreme ultraviolet time-resolved photoelectron spectroscopy (EUV-TRPES) with 18 fs time resolution.
- Studied the photoexcitation and subsequent dynamics of indole, phenol, and phenolate at the air-water interface.
- Analyzed concentration-dependent dynamics attributed to interfacial molecular aggregation.
Main Results:
- Interfacial indole showed faster decay of valence excited states and electron-cation pairs compared to bulk solution.
- Interfacial phenol primarily formed valence excited states, with no detectable hydrated electrons.
- Interfacial phenolate exhibited faster photodetachment than in bulk solution.
- Observed 5 fs internal conversion and vibrational quantum beats in interfacial indole.
Conclusions:
- EUV-TRPES is a powerful technique for observing electronic and vibrational dynamics at interfaces.
- Interfacial solvation environments can influence photoinduced charge-separation dynamics.
- Molecular aggregation at interfaces affects reaction dynamics in a concentration-dependent manner.
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