Visualizing site-specific redox potentials on the surface of plasmonic nanoparticle aggregates with superlocalization...

Area of Science:

• Electrochemistry
• Surface Science
• Spectroscopy

Background:

• Understanding redox potentials at the nanoscale is crucial for electrochemical applications.
• Nile Blue dye serves as a model redox probe for surface interactions.
• Surface-enhanced Raman scattering (SERS) offers high sensitivity for molecular detection.

Purpose of the Study:

• To demonstrate site-specific redox potential mapping of Nile Blue on silver nanoparticle electrodes.
• To correlate electrochemical modulation with optical readouts using SERS.
• To investigate the behavior of adsorbed molecules under applied electrical potentials.

Main Methods:

• Utilized surface-enhanced Raman scattering (SERS) superlocalization microscopy.
• Electrocatalytically modulated Nile Blue between oxidized and reduced states.
• Determined emitter locations with 5-10 nm precision by fitting SERS emission to a 2D Gaussian.

Main Results:

• Observed reversible shifts in SERS emission centroids with applied potential.
• Demonstrated molecular coverage above the single-molecule level.
• Showcased distinct redox behavior based on molecular location on the nanoparticle surface.

Conclusions:

• Proposed a mechanism explaining centroid trajectories by site-specific redox potentials.
• The first molecule reduced was the last to be oxidized, indicating reversible electrochemical behavior.
• This work provides insights into nanoscale electrochemical processes and surface interactions.