Surface-Sensitive and Surface-Specific Ultrafast Two-Dimensional Vibrational Spectroscopy.

Area of Science:

• Physical Chemistry
• Spectroscopy
• Surface Science

Background:

• Ultrafast two-dimensional infrared spectroscopy (2D IR) has advanced to detect monolayer molecules at interfaces.
• Various 2D IR techniques, including 2D sum-frequency-generation (2D SFG), transmission, and reflection (ATR, external) 2D IR, have been developed.

Purpose of the Study:

• To review the principles, technological aspects, benefits, and shortcomings of 2D vibrational spectroscopy at surfaces.
• To discuss the broad applications of 2D vibrational surface spectroscopy.
• To highlight recent technological developments and future outlooks.

Main Methods:

• Overview of 2D sum-frequency-generation (2D SFG), transmission 2D IR, and reflection 2D IR techniques.
• Discussion of methods based on even-order or odd-order nonlinear susceptibility.
• Exploration of surface enhancement, electrochemical interface studies, and transient 2D IR.

Main Results:

• 2D vibrational spectroscopy resolves molecular temporal and spectral information at interfaces.
• Applications span biological molecules to heterogeneous catalysts, focusing on ultrafast dynamics, environmental, and intermolecular interactions.
• Recent advancements include surface enhancement, electrochemical interface methods, and transient 2D IR for nonequilibrium processes.

Conclusions:

• 2D vibrational surface spectroscopy is a powerful tool for investigating molecular dynamics at interfaces.
• Continued technological development promises expanded applications in diverse scientific fields.
• The review provides a comprehensive overview and outlook for this rapidly evolving technique.