Scanning electrochemical microscopy. 41. Theory and characterization of ring electrodes

Y. Lee, S. Amemiya, A. J. Bard

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Ring ultramicroelectrodes, which are of particular interest as probes for scanning electrochemical microscopy (SECM), combined with near-field scanning optical microscopy, were investigated. Theoretical SECM tip current-distance (approach) curves for a ring electrode were calculated by numerical (finite element) analysis. The SECM curves obtained were a function of the geometry of the tips including the thickness of the ring and the insulating sheath. Theoretical approach curves over conductive substrates showed a strong dependence on the ratio of inner to outer radii of ring microelectrodes (a/b) and were relatively insensitive to the thickness of the insulating sheath (rg). For insulating substrates, however, the approach curves varied significantly with rg, but much less with the a/b ratio. Comparison of experimental and theoretical SECM curves provided a good method of evaluating the size and shape of ring electrodes. Good agreement of the experimental and theoretical curves was found with a ring microelectrode with a nominal 200-nm ring thickness, yielding values of 1.7, 1.9, and 5.7 μm for the inner (a) and outer (b) radii of a ring and the outermost radius of insulating sheath (rg), respectively.

Original languageEnglish
Pages (from-to)2261-2267
Number of pages7
JournalAnalytical Chemistry
Issue number10
StatePublished - 15 May 2001


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