SURFACE-PROPERTIES OF FRACTURED AND POLISHED PLATINUM MICROELECTRODES

An investigation of the surface properties related to the method of mi croelectrode fabrication is presented and discussed. The voltammetric response in acidic media (sulphuric and formic acids) of fractured 25 mu m diameter wire which had been sealed in soft glass was used to inv estigate the surface microstructure. SEM studies showed that the cryst allite size of the fractured wire, which had previously been sealed in glass, was large, and that a single crystallite may be exposed to the solution surface. The effect of sealing the wire in glass on the bulk properties of the wire is related to the voltammetric response in aci d media. Thus, the surface of a polished platinum microelectrode seale d in glass cannot be considered as truly polycrystalline. The response s of fractured platinum wire sealed in soft glass in sulphuric acid an d formic acid are predominantly Pt(111), when compared by non-linear r egression and congruent analysis with the three low index faces of pla tinum in the same acidic medium under the same conditions. This is exp lained by the process of slip deformation, which involves the slipping of Pt(111) planes (close packed planes or planes of highest atomic de nsity) forming steps with the exposed surface predominantly Pt(111).