Scan-Rate-Induced Transition from Redox to Ion Current Rectification in Carbon Nanopipettes.

Area of Science:

• Electrochemistry
• Nanotechnology
• Physical Chemistry

Background:

• Electrochemical performance relies on ion transport and electron transfer.
• These processes have distinct mechanisms and offer complementary insights.
• Decoupling these signals is crucial for understanding nanoelectrochemical systems.

Purpose of the Study:

• To present a method for decoupling ion transport and electron transfer in carbon nanopipettes.
• To demonstrate the tunability of electrochemical and iontronic signals via scan rate.
• To enable the observation of ion concentration-redistribution (ICR) in nanofluidic devices.

Main Methods:

• Utilized cyclic voltammetry (CV) to analyze carbon nanopipette electrochemical performance.
• Varied scan rates from below 0.1 V s⁻¹ to 1 V s⁻¹ to differentiate charge transport mechanisms.
• Employed asymmetric and charged nanofluidic devices to study ICR.

Main Results:

• At low scan rates (<0.1 V s⁻¹), redox reactions dominate, showing distinct peaks.
• At high scan rates (>0.5 V s⁻¹), ion transport becomes the primary driver of the response.
• Successfully observed ICR in the 0.5-1 V s⁻¹ range, transitioning from pure redox behavior.

Conclusions:

• Scan rate adjustment allows for selective observation of electron transfer or ion transport signals.
• This tunable strategy facilitates the study of complex nanoelectrochemical systems.
• Enables the development of sensors that leverage both electrochemical and iontronic signals.