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Electrochemical Display through use of a Redox Couple in Solution. January 1975

IP.com Disclosure Number: IPCOM000082742D
Original Publication Date: 1975-Jan-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 1 page(s) / 8K

Publishing Venue

IBM

Related People

Horkans, WJ: AUTHOR [+2]

Abstract

Some solutions of tungsten salts and some viologen derivatives undergo transformation from a colorless to a highly colored form, depending on their oxidation state, and thus have been considered for use in electrochemical displays. Other compounds form intense colors when reduced or oxidized.

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Electrochemical Display through use of a Redox Couple in Solution

Some solutions of tungsten salts and some viologen derivatives undergo transformation from a colorless to a highly colored form, depending on their oxidation state, and thus have been considered for use in electrochemical displays. Other compounds form intense colors when reduced or oxidized.

The color transformation rate is controlled by the rate of diffusion of the reactant to the electrode (generally slow), and the rate of charge transfer at the electrode (generally fast compared to diffusion).

The dwell time of a colored species depends on its stability and the strength of its interaction with the electrode due to physical, electrical, or chemical forces. If loosely held, it diffuses away from the electrode and slowly imparts color to the solution. Thus, display contrast is decreased and the colorless form is consumed. The colorless species can be regenerated at the electrode surface while it remains there. Once the colored species diffuses away from the electrode into solution, however, this regeneration becomes diffusion controlled and is slow.

In systems where color forms by colorless form reduction, addition of an oxidizing species with a suitable electrochemical potential can result in considerable color contrast improvement and color-forming species regeneration. Oxidizing agents used are H(2)O(2), MnO/-/(4), CrO/2-/(4), O(2) Fe(III) and Ce(IV). Oxidant choice is limited to colorless solu...