Universal control of proton concentration using an electrochemically generated acid compatible with miniaturization

Area of Science:

• Electrochemistry
• Chemical Engineering
• Materials Science

Background:

• Precise control of local acidity is crucial for managing simultaneous chemical reactions in miniaturized systems.
• Existing methods often lack the spatial resolution or control needed for complex reactions in small volumes.

Purpose of the Study:

• To develop and demonstrate a platform for electrochemical control of acidity in nanoliter (nL) volumes.
• To achieve localized chemical reactions with high proton concentrations and controlled acidity contrasts.

Main Methods:

• Utilized miniaturized micro-reactors for electrochemical control of acidity.
• Employed a sulfonated tetrafluoroethylene-based membrane to isolate acid-generating electrodes.
• Demonstrated control in both aqueous and organic solvents.
• Quantified acidity control using carboxyfluorescein calibration and a pH 4.2 tautomer transition.

Main Results:

• Achieved precise local control of acidity in a 150 μm diameter region.
• Generated high proton concentrations (∼10⁻¹ M) with significant acidity contrasts.
• Successfully controlled chemical reactions in organic electrolytes.
• Demonstrated quantitative control of acidity via faradaic currents.

Conclusions:

• The developed platform offers unprecedented control of acidity in the smallest reported volumes.
• This technology enables precise management of chemical reactions at the microscale.
• The platform shows potential for applications requiring localized pH manipulation.