Visualizing and Calculating Tip-Substrate Distance in Nanoscale Scanning Electrochemical Microscopy Using...

Area of Science:

• Nanoscale Science
• Analytical Chemistry
• Microscopy

Background:

• Scanning electrochemical microscopy (SECM) requires precise control of tip-substrate distance for accurate measurements.
• Existing methods for distance determination can be limited in precision and applicability.
• Optical techniques offer potential for non-invasive and high-resolution distance sensing.

Purpose of the Study:

• To develop and validate an optical strategy for determining tip-substrate distance in SECM using super-resolution fluorescence imaging.
• To achieve high precision (< 25 nm) in tip-substrate distance measurements.
• To extend the applicability of optical distance determination to non-fluorogenic electrochemical reactions.

Main Methods:

• Utilized a dual SECM/optical microscope equipped with a phase mask to generate a double helix point spread function.
• Excited a fluorogenic reaction at the SECM tip and fluorescent nanoparticles on the substrate.
• Attached a fluorescent particle to the SECM tip for non-fluorogenic reactions.
• Employed three-dimensional super-resolution fluorescence imaging for height measurement.

Main Results:

• Achieved tip-substrate distance measurement precision better than 25 nm.
• Demonstrated successful application to both fluorogenic and non-fluorogenic electrochemical reactions.
• Showed excellent agreement between correlated optical and electrochemical distance determinations.
• Validated the utility of super-resolution imaging for tip alignment and accounting for electrode tilt.

Conclusions:

• Super-resolution fluorescence imaging provides a robust optical feedback mechanism for SECM.
• The developed method enhances precision and expands the scope of SECM applications.
• This technique offers facile tip alignment and improved accuracy in gap control during SECM experiments.