Imaging transient formation of diffusion layers with fluorescence-enabled electrochemical microscopy

Area of Science:

• Electrochemistry
• Analytical Chemistry
• Microscopy

Background:

• Ultramicroelectrodes (UMEs) are crucial in electrochemical studies.
• Imaging dynamic concentration profiles around UMEs is challenging.
• Existing methods lack the resolution and speed for transient phenomena.

Purpose of the Study:

• To introduce Fluorescence-enabled electrochemical microscopy (FEEM) as a novel imaging technique.
• To demonstrate FEEM's capability for visualizing diffusion layers around UMEs.
• To enable 2D and 3D imaging of transient concentration profiles.

Main Methods:

• FEEM couples redox reactions to fluorogenic reporters via bipolar electrodes.
• An array of thousands of bipolar electrodes is used for imaging.
• FEEM captures 2D lateral cross-sections and builds 3D images from multiple sections.

Main Results:

• FEEM successfully imaged the diffusion layer of a 10 μm carbon fiber electrode.
• FEEM-generated images were compared with numerical simulations.
• Diffusion layers of a two-electrode array were imaged during a potential step experiment.

Conclusions:

• FEEM is a powerful new technique for imaging transient electrochemical processes.
• The method allows for detailed visualization of diffusion layers in 2D and 3D.
• FEEM offers a significant advancement in understanding electrochemical reactions at the microscale.