Electrochemical Tip-Enhanced Raman Spectroscopy with Improved Sensitivity Enabled by a Water Immersion Objective

Area of Science:

• Electrochemistry
• Spectroscopy
• Nanoscience

Background:

• Electrochemical tip-enhanced Raman spectroscopy (EC-TERS) is a powerful tool for studying electrochemical interfaces at the nanoscale.
• Existing EC-TERS setups suffer from low sensitivity due to optical path distortion caused by refractive index mismatches.
• This limitation hinders the widespread application of EC-TERS for detailed interfacial analysis.

Purpose of the Study:

• To develop a novel EC-TERS setup that overcomes sensitivity limitations caused by optical distortions.
• To enable highly sensitive in situ monitoring of electrochemical processes at the molecular level.
• To investigate the synergistic effects of electrochemical potential and laser illumination on interfacial reactions.

Main Methods:

• A side-illumination EC-TERS configuration was designed using a high numerical aperture water immersion objective.
• The setup incorporated a scanning tunneling microscope with a customized scanning head and a compact spectroelectrochemical cell.
• Independent control over tip position and laser illumination position was achieved for nanoscale manipulation.

Main Results:

• The new setup effectively eliminated optical distortions, leading to a remarkable increase in EC-TERS sensitivity.
• Sensitive monitoring of anthraquinone molecule redox processes was achieved.
• The study revealed that anthraquinone reduction is driven by a synergy between negative potential and laser illumination, not solely localized surface plasmons.

Conclusions:

• The developed side-illumination EC-TERS system offers significantly improved sensitivity and precise nanoscale control.
• This advancement provides a crucial tool for fundamental research in photo- and plasmon electrochemistry.
• The findings enable deeper understanding of interfacial structure-activity relationships in electrochemical systems.