Variable-Temperature Tip-Enhanced Raman Spectroscopy of Single-Molecule Fluctuations and Dynamics

Area of Science:

• Physical Chemistry
• Spectroscopy
• Nanotechnology

Background:

• Molecular structure, dynamics, and coupling are crucial for function in various systems.
• Vibrational spectroscopy offers molecular structure insights, but rapid fluctuations limit single-molecule studies.
• Current methods often involve spatial averaging, obscuring dynamic processes.

Purpose of the Study:

• To investigate intramolecular coupling, substrate coupling, and dynamic processes at the single-molecule level.
• To overcome limitations of conventional spectroscopy by controlling molecular motion.
• To enable quantitative analysis of vibrational modes and molecular dynamics.

Main Methods:

• Utilized tip-enhanced Raman spectroscopy (TERS) at variable and cryogenic temperatures.
• Controlled single-molecule motion to slow down rapid fluctuations.
• Employed statistical correlation analysis of spectral fluctuations.

Main Results:

• Resolved intrinsic line widths of individual normal modes for quantitative vibrational analysis.
• Quantified ultrafast vibrational dephasing, intramolecular coupling, and conformational heterogeneity via temperature-dependent line narrowing and splitting.
• Observed rotational motion and spectral fluctuations through mode correlation analysis.

Conclusions:

• Demonstrated single-molecule vibrational spectroscopy capable of detailed molecular motion analysis.
• Opened possibilities for a comprehensive understanding of molecular dynamics from femtoseconds to minutes.
• Advanced TERS for applications beyond chemical identification, probing dynamic processes.