Scanning electrochemical microscopy. 32. Gallium ultramicroelectrodes and their application in ion-selective probes

Area of Science:

• Electrochemistry
• Analytical Chemistry
• Materials Science

Background:

• Scanning electrochemical microscopy (SECM) is a powerful technique for high-resolution surface analysis.
• Ultramicroelectrodes are crucial for SECM due to their enhanced mass transport and low capacitive current.
• Gallium (Ga) offers unique properties for electrode fabrication, but its application in SECM requires specialized methods.

Purpose of the Study:

• To fabricate novel gallium ultramicroelectrodes for amperometric measurements in SECM.
• To demonstrate the utility of these Ga electrodes for SECM imaging using a redox probe.
• To construct and test a dual-mode probe combining a Ga amperometric electrode with an ion-selective electrode.

Main Methods:

• Fabrication of Ga ultramicroelectrodes by introducing liquid Ga into pulled glass micropipets.
• Cyclic voltammetry of hexaaminruthenium(III) chloride (Ru(NH3)6(3+)) to characterize electrode performance.
• SECM imaging using the Ga electrode and Ru(NH3)6(3+).
• Construction of double-barrel micropipets integrating a Ga amperometric electrode and a potassium ion (K+) selective potentiometric probe.

Main Results:

• Successfully fabricated Ga ultramicroelectrodes suitable for amperometric measurements.
• Demonstrated SECM imaging capabilities using the Ga electrode and Ru(NH3)6(3+).
• Developed a dual-probe system capable of simultaneous electrochemical and potentiometric measurements.
• Successfully imaged K+ activity near a glass capillary lumen using the dual-probe system.

Conclusions:

• Gallium ultramicroelectrodes are viable for SECM applications, offering a new material for electrochemical sensing.
• The developed Ga electrodes facilitate high-resolution imaging of redox species.
• The integration of amperometric and potentiometric probes in a single tip expands the analytical capabilities of SECM for multi-analyte detection.