Visualization of hydrogen isotope exchange in single molecule by tip-enhanced Raman images

Area of Science:

• Nanoscale Science
• Spectroscopy
• Physical Chemistry

Background:

• Intramolecular hydrogen isotope exchange (HIE) influences molecular properties.
• Observing HIE at the single-molecule level is difficult with conventional methods.
• Accurate counting and locating substituted atoms in HIE is challenging.

Purpose of the Study:

• To theoretically demonstrate tip-enhanced Raman scattering (TERS) for visualizing intramolecular HIE.
• To identify various hydrogen-to-deuterium isotope substitution configurations.
• To precisely determine atom positions and isotopic categories in single molecules.

Main Methods:

• Theoretical demonstration using coronene as a model system.
• Utilizing tip-enhanced Raman scattering (TERS) modulated by vibrational interference.
• Overlaying mode-specific TERS images at characteristic vibrational frequencies.

Main Results:

• TERS can distinguish and identify various hydrogen-to-deuterium isotope substitution configurations.
• The approach precisely determines the number and spatial positions of exchanged atoms.
• Isotopic categories (deuterium/tritium) of exchanged atoms are identified in individual molecules.

Conclusions:

• TERS imaging is a powerful technique for direct visualization of intramolecular isotopic transformations.
• This method provides new insights into quantum vibrational dynamics.
• It offers a new way to study interference-mediated reaction pathways at the nanoscale.