Molecular Perturbation Effects in AFM-Based Tip-Enhanced Raman Spectroscopy: Contact versus Tapping Mode

Area of Science:

• Surface Science
• Nanotechnology
• Spectroscopy

Background:

• Tip-enhanced Raman spectroscopy (TERS) enables label-free chemical characterization at the nanoscale.
• The atomic force microscopy (AFM) probe interaction can perturb soft samples during TERS analysis, despite its non-destructive nature.
• Understanding AFM feedback modes is crucial for preserving sample integrity in TERS.

Purpose of the Study:

• To investigate the impact of AFM feedback modes (contact vs. tapping) on molecular perturbation in TERS.
• To evaluate the influence of these modes on TERS signal quality for soft samples.

Main Methods:

• TERS analysis of a 2-chloro-4-nitrobenzene-1-thiol (Cl-NBT) self-assembled monolayer (SAM) on a soft substrate.
• Comparison of TERS signal and molecular perturbation under AFM contact mode and tapping mode feedback.
• Utilized atomic force microscopy (AFM) for precise probe positioning and feedback control.

Main Results:

• Tapping mode AFM feedback resulted in significantly less molecular perturbation of the Cl-NBT SAM.
• Tapping mode consistently yielded a higher TERS signal compared to contact mode.
• Minimal sample alteration was observed with tapping mode, preserving molecular organization.

Conclusions:

• Tapping mode is preferable to contact mode for TERS analysis of soft and delicate samples.
• This finding provides critical insights for optimizing AFM-TERS operation for sensitive materials.
• The study is expected to accelerate TERS applications in nanoscale chemical analysis of soft matter.