Spatially Resolved Ion Sensing by Voltammetric Ion Transfer Microscopy.

Area of Science:

• Electrochemistry
• Analytical Chemistry
• Materials Science

Background:

• Visualizing ionic species is crucial for understanding chemical gradients and dynamic processes.
• Current label-free methods for ion mapping are often slow or limited in scope.
• There is a need for high-frequency, spatially resolved sensing of optically silent ionic species.

Purpose of the Study:

• To introduce a novel chemical mapping principle for high-frequency, spatially resolved sensing of ionic species.
• To develop a method for acquiring concentration maps with millions of pixels in seconds.
• To demonstrate a new chemical imaging platform using a conventional fluorescence microscope.

Main Methods:

• Utilizing ion transfer from a polymeric film into a solution, coupled with electrochemical electron transfer.
• Visualizing ion transfer by monitoring fluorescence quenching/unquenching of a redox probe.
• Capturing rapid image bursts to determine excitation peak potentials for each pixel.
• Employing a flowing junction to map diffusional mixing of solutions with varying ion concentrations.

Main Results:

• Achieved high-frequency, spatially resolved sensing of optically silent ionic species.
• Generated concentration maps with millions of pixels in seconds.
• Demonstrated micrometer spatial resolution in mapping ion concentrations.
• Successfully mapped diffusional mixing of solutions using tetraethylammonium as a model ion.

Conclusions:

• The novel principle enables a new chemical imaging platform for sensing ionic species.
• This method overcomes the speed and parameter limitations of existing label-free approaches.
• The technique offers a powerful tool for studying chemical gradients and dynamic processes at high resolution.