417 .I. Electroanal. Chem., 217 (1987) 417-423 Elsevier Sequoia S.A., Lausanne - Printed in The Netherlands zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPO Short comtnnnication CHRONOAMPEROMETRIC CURRENT AT HEMICYLINDER AND BAND MICROELEtXRODEs: THEORY AND EXPERIMENT ATTILA SZABO Laboratory of Chemical Physics, National Instttute of Diabetes and Dtgestive and Kidney Diseases, Budding 2, Room Bl-28, National Instttutes of Health, Bethesda, MD 20892 (U.S.A.) DAVIS K. COPE Division of Mathematrcal Sciences, North Dakota State University, Fargo, ND 58105 (U.S.A.) DENNIS E. TALLMAN Department of Chemistry, North Dakota State University, Fargo, ND 58105 (U.S.A.) PAUL M. KOVACH and R. MARK WIGHTMAN Department of Chemistry, Indiana University, Bhwmtngton, IN 47405 (U.S.A.) (Received 16th May 1986; in revised form 23rd July 1986) INTRODUCTION zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA The construction of ultramicroelectrodes with the geometry of a band has been shown to be feasible with a number of relatively simple techniques [l-3]. Electrodes with this geometry have been made with the smallest dimension less than 10 nm [4]. Applications proposed for these devices include analytical sensors [2,4] and molecu- lar electronic devices [3]. Since these electrodes are microscopic in one dimension, they share the feature of other ultramicroelectrodes of a significantly reduced zyxwvutsrqponml iR drop. Thus, this type of electrode is useful in highly resistive media or over a wide range of time scales. Furthermore, the finite length of these electrodes results in currents that are sufficiently large that conventional instrumentation can be em- ployed. Despite the advantages of band electrodes, progress in research with these devices has been impeded by the lack of an exact description of the convergent diffusion processes which occur at these electrodes. The amperometric response at band electrodes deviates significantly from that predicted for planar diffusion at all but the shortest times. It has been suggested [l] that the current at a band electrode of width w at long times can be approximated by the current at a hemicylinder electrode with the same area (i.e., with radius (w/ a)). In this paper we show that the long-time current at a band is in fact equal to that at a hemicylinder with radius 0022-0728/87/$03.50 0 1987 Elsevier Sequoia S.A.