Observing Discrete Blocking Events at a Polarized Micro- or Submicro-Liquid/Liquid Interface

Area of Science:

• Electrochemistry
• Nanotechnology
• Analytical Chemistry

Background:

• Single-entity electrochemistry (SECE) offers single-entity resolution for particle characterization.
• Traditional SECE and Coulter counters face limitations with particle detection and translocation speed.
• Existing methods struggle to analyze redox-inactive or rapidly translocating particles.

Purpose of the Study:

• To develop a novel SECE method for characterizing single nanoparticles at liquid/liquid interfaces.
• To overcome the limitations of traditional solid electrode-based SECE and Coulter counters.
• To demonstrate the ability to study both conductive and insulating nanoparticles.

Main Methods:

• Utilizing a miniaturized polarized liquid/liquid interface for ion transfer (IT) blockade.
• Observing the blocking effect of single nanoparticles (NPs) adsorbing at the interface.
• Analyzing current transients resulting from NP electromigration and interfacial assembly.
• Calculating NP size from electrochemical blocking events and comparing with dynamic light scattering (DLS).

Main Results:

• Successfully observed the ion transfer blockade effect by single conductive and insulating nanoparticles at a liquid/liquid interface.
• Demonstrated that interfacial NP assembly effectively shields ion transfer flux.
• Quantized nanoparticle size by measuring the step height of current transients.
• Achieved good agreement between NP sizes determined electrochemically and by DLS.

Conclusions:

• Proven the experimental feasibility of single-entity ion transfer blockade at micro/submicro liquid/liquid interfaces.
• Established a new SECE approach for analyzing diverse nanoparticles, including conductive and insulating types.
• This method provides a valuable reference for advancing single-entity detection technologies.