HR: 09:45h
AN: B51F-08    [Abstracts]
TI: Scaleable Nitrate Microsensors in the Form of a Plant Root
AU: * Harmon, T C
EM: tharmon@ucmerced.edu
AF: School of Engineering, University of California, P.O. Box 2039, Merced, CA 95344 United States
AU: Jurisch, N L
AF: School of Engineering, University of California, P.O. Box 2039, Merced, CA 95344 United States
AU: Davidson, M J
AF: Department of Chemical Engineering, University of Washington, 105 Benson Hall, Seattle, WA 98195 United States
AU: Haux, J E
AF: School of Engineering, University of California, P.O. Box 2039, Merced, CA 95344 United States
AB: This work describes the development of flexible, miniature and inexpensive nitrate sensors by electropolymerizing pyrrole onto carbon fiber substrates, using nitrate as a dopant. Carbon microfibers were found to be an excellent substitute to expensive conductive materials, such as glassy carbon or platinum. The electrodes with a 3-5 micron layer of NO3 -doped polypyrrole (PPy) exhibited a promising lifetime (at least 2 month without changes in sensitivity and linear response), fast response times (seconds), and sensitivity competitive to commercial nitrate ISE. Nernstian sensor response slopes of 54 to 58 mV/(decade concentration) for single filament have been observed, with a linear response to nitrate concentrations spanning three orders of magnitude (0.1 - 10-4 M or 6200 - 6.2 ppm of NO3-), and a detection limit of (3  1) x 10-5 M (1.25-2.5 ppm). An advantage of using the carbon fibers as a substrate for pyrrole polymerization process is that these fibers are relatively easy to manipulate, lending themselves to root-like electrode designs which may be ideal for observing the water chemistry of soil moisture. Using prototypical PPy-coated microfibers, we have been able to directly measure nitrate concentrations in residual soil water contents as low as 8 percent by weight for a medium sand. Results for model soils and field samples are presented in which direct measurements with the microsensors compare reasonably well with a more conventional analytical method entailing soil extraction and analysis by the Griess-Romijn method.
DE: 1800 HYDROLOGY
DE: 1030 Geochemical cycles (0330)
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting