Femtomole Infrared Spectroscopy at the Electrified Metal-Solution Interface

Area of Science:

• Surface science
• Spectroscopy
• Electrochemistry

Background:

• In situ infrared (IR) spectroscopy is crucial for understanding interfacial processes but faces limitations with small surface areas.
• Obtaining high signal-to-noise (S/N) spectra from femtomole quantities of adsorbed molecules on micrometer-scale electrodes remains a challenge.

Discussion:

• A novel methodological breakthrough couples synchrotron-sourced infrared microscopy with attenuated total reflection surface enhanced infrared spectroscopy (ATR-SEIRAS).
• This advanced technique allows for spectral measurement of a monolayer of 4-methoxypyridine (MOP) on a gold film electrode under operational electrochemistry conditions.
• Synchrotron IR provides a significant noise improvement (factor of 15) compared to thermal IR sources, especially with small apertures.

Key Insights:

• High-quality IR spectra can be obtained from as little as 2.5 fmol of molecules within a 125 μm² beam spot.
• The method overcomes the IR diffraction limit for micrometer-scale surfaces.
• Demonstrates the capability for detailed molecular-level analysis of interfacial phenomena.

Outlook:

• This breakthrough opens new avenues for in situ surface characterization at the femtomole level.
• Potential applications in catalysis, electrochemistry, and sensor development.
• Enables deeper understanding of interfacial chemical and physical processes with unprecedented sensitivity.