ELECTROCHEMILUMINESCENCE AT BAND ARRAY ELECTRODES

Electrochemiluminescence (ECL) arising from ion-annihilation reactions has been examined at a double-band electrode. The double band consists of two individually addressable parallel electrodes, each 4-mu-m wide, separated by a gap of similar dimensions, and the array has a length of approximately 0.5 cm. The array can be used to evaluate the stability of the electrochemically generated reactants when used in the collector-generator mode. For the generation of ECL, one band serves as the anode and the other as the cathode. ECL was generated with Ru(bpy)3(ClO4)2 or diphenylanthracene in acetonitrile containing electrolyte. These compounds produce emission when the oxidized and reduced forms of the electrochemically generated ions react in the volume of solution which is spatially restricted to the region adjacent to the array. The time course of the light emission gives evidence for an expanding diffusion layer during steady-state generation of ECL reactants. The double-band geometry is shown to be a highly efficient way to generate steady-state ECL. It is comparable in efficiency to a triple band operated as a central cathode with two flanking anodes. The device can be used to explore ECL in solutions of low ionic strength with minimal distortion from ohmic drop.