Counting Single Redox Molecules in a Nanoscale Electrochemical Cell

Area of Science:

• Electrochemistry
• Nanotechnology
• Analytical Chemistry

Background:

• Single-molecule detection is crucial for understanding complex chemical and biological processes.
• Existing methods often lack the sensitivity or specificity required for analyzing individual redox events.
• Electrochemical nanodevices offer potential for high-resolution analysis at the molecular level.

Purpose of the Study:

• To develop and demonstrate a novel platinum bipolar electrochemical nanocell for single redox molecule detection.
• To utilize fluorescence for sensitive and quantitative analysis of individual redox events.
• To establish a method for estimating detection efficiency through single-molecule counting.

Main Methods:

• Fabrication of a platinum (Pt) bipolar electrochemical nanocell by depositing a Pt particle at a nanopipet orifice.
• Generation of highly fluorescent resorufin molecules on the inner Pt surface.
• Optical detection and counting of single fluorescent resorufin molecules using a horizontally positioned microscope.
• Exploitation of nanocell properties (pipet positioning, confinement, diffusion distance) to enhance fluorescence detection.

Main Results:

• Successful detection and counting of single redox molecules (resorufin) within the nanocell.
• Achieved high signal-to-background ratio due to molecular confinement in the 100 nm pipet.
• Demonstrated the ability to estimate detection efficiency by counting individual molecules.
• Validated the power of fluorescence-based electrochemical detection for single redox events.

Conclusions:

• The developed Pt bipolar electrochemical nanocell provides a powerful platform for single redox molecule detection.
• This technique offers high sensitivity and quantitative analysis capabilities for electrochemical events.
• Future applications may extend to studying non-fluorescent redox reactions and single enzymes or catalysts.