Reversible, colorimetric fiber-optic sensors are undergoing development for use in measuring concentrations of ammonia in air at levels relevant to human health [0 to 50 parts per million (ppm)]. A sensor of this type includes an optical fiber that has been modified by replacing a portion of its cladding with a polymer coat that contains a dye that reacts reversibly with ammonia and changes color when it does so. The change in color is measured as a change in the amount of light transmitted from one end of the fiber to the other. Responses are reversible and proportional to the concentration of ammonia over the range from 9 to 175 ppm and in some cases the range of reversibility extends up to 270 ppm. The characteristic time for the response of a sensor to rise from 10 to 90 percent of full scale is about 25 seconds. These sensors are fully operational in pure carbon dioxide and are not adversely affected by humidity.

This work was done by Michael T. Carter of Eltron Research, Inc., for Kennedy Space Center. For further information, please contact:

Dr. Michael Carter

4600 Nautilus Court South

Boulder, CO 80301-3241

Tel. No.: (303) 530-0263 Ext. 113

E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.


NASA Tech Briefs Magazine

This article first appeared in the January, 2003 issue of NASA Tech Briefs Magazine.

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