Micro-/Nanopipettes are used in SECM-related techniques:
- Scanning ion conductance microscopy (SICM)
- Scanning micropipette contact method (SMCM)
- Scanning electrochemical cell microscopy (SECCM)
The pipettes are filled with electrolyte solution and an Ag/AgCl wire is inserted into the pipette which acts as a quasi-reference-counter electrode (QRCE). For measuring ion conductance currents, the current between the QRCE inside the pipette and one in the bulk solution or second pipette barrel inside a theta capillary is determined.
In SICM the ion conductance current between one quasi-reference-counter electrode (QRCE) inside the micropipette and one in the bulk solution is measured. The substrate is immersed in electrolyte. Upon approaching a surface, the ion conductance current decreases due to hindered diffusion between micropipette opening and the surface. This allows non-contact high-resolution topography imaging.
SMCM and SECCM
In SMCM and SECCM the solution-filled micropipette is operated in air, as well as the substrate. At the opening of the micropipette a droplet is formed. At close proximity to the substrate surface, the droplet creates a miniature electrochemical cell by locally wetting the surface.
In this electrochemical cell where the substrate is connected as the working electrode (WE) and the Ag/AgCl wire as the QRCE, spatially resolved localized electrochemical techniques, such as:
- Micro-CV and micro-fabrication for conductive polymers
- Localized characterization of battery materials
- Micro-EIS and micro-Tafel for localized corrosion studies
- Combined electrocatalysis and topography imaging for nanomaterials
SECM - SICM
Using theta-micropipettes (double-barrel micropipettes) enables the combination of SECM and SICM in one scan. One barrel is filled with electrolyte solution and an Ag/AgCl wire is inserted. In the other barrel, carbon is deposited to create a microelectrode tip. Topography imaging is performed by measuring the ion conductance current through the electrolyte-filled barrel (SICM). Electrochemical properties are simultaneously probed by the microelectrode (SECM).