Simple procedure for the fabrication of silver/silver chloride potentiometric electrodes with micrometre and smaller dimensions: application to scanning electrochemical microscopy

A simple method is described for the fabrication of silver/silver chloride electrodes with micrometre and smaller dimensions. The electrodes are constructed by etching a silver wire to a fine point and then coating with an electrophoretically-deposited paint, which is subsequently heat-cured to insulate all but the very end of the tip. These electrodes have effective radii in the 50 nm to 1 μm range (assuming a hemispherical geometry), as determined by steady-state linear sweep voltammetry. After depositing AgCl on the Ag surface, by anodic oxidation in aqueous KCl solution, the electrodes exhibit Nernstian behaviour to chloride ions, in potentiometric measurements, over a concentration range of 10−4 to at least 10−1 mol dm−3. These electrodes are shown to be particularly promising as scanning electrochemical microscopy (SECM) probes for imaging local chloride concentrations.