Visualizing and tuning thermodynamic dispersion in metalloprotein monolayers

Area of Science:

• Electrochemistry
• Surface Science
• Spectroscopy

Background:

• Redox state imaging is crucial for understanding electron transfer at interfaces.
• Molecular dispersion and surface order influence thermodynamic properties.
• Self-assembled monolayers (SAMs) can tune electronic coupling and molecular behavior.

Purpose of the Study:

• To investigate the impact of supporting monolayer crystallinity on the redox potential dispersion of adsorbed molecules.
• To develop a method for directly imaging and quantifying redox profiles at the molecular scale.
• To explore tuning molecular dispersion through surface modification.

Main Methods:

• Far-field fluorescence imaging to couple molecular redox state to spectral characteristics.
• Utilizing optically transparent electrode surfaces for observing interfacial electron transfer.
• Quantifying thermodynamic dispersion by mapping switching potentials across surface populations.
• Analyzing the effect of alkanethiol layer crystallinity on the blue copper protein azurin.

Main Results:

• Direct imaging of redox profiles at scales approaching the molecular level is achieved.
• Thermodynamic dispersion, influenced by orientation, electronic coupling, and surface order, can be quantified.
• The crystallinity of the supporting alkanethiol monolayer significantly contributes to the spread in half-wave potentials.
• Increasing monolayer crystallinity reduced the redox potential spread for azurin from 17 mV to 12 mV.

Conclusions:

• Supporting monolayer crystallinity is a key factor in tuning the redox character of adsorbed molecules.
• Surface and chemical modifications offer a means to control and reduce molecular dispersion in redox properties.
• This work provides a method for direct determination and tuning of submonolayer scale variance in redox character.