Polyaniline Nanofibers and Composite Materials for Chemical Detection
B.H. Weiller, S. Virji, C. Baker, J. Huang, D. Li and R.B. Kaner
The Aerospace Corporation, US
chemical sensor, polyaniline, nanofiber
Polyaniline is a conducting polymer with electrical properties that can change greatly upon exposure to various chemicals. Most notably, when polyaniline is exposed to strong acids and bases, the conductivity changes by greater than 8 orders of magnitude. Recently, we have developed a simple, template-free chemical synthesis for polyaniline nanofibers. This interfacial polymerization is selective for nanofibers, can be readily scaled to make large quantities and can be controlled to selectively produce nanofibers with narrow distributions. Chemical sensors are fabricated from polyaniline nanofibers by casting films on microelectrode arrays. The nanofibers have significantly better performance than conventional material in both sensitivity and time response for all analytes tested including acids, bases, hydrazine, and organic vapors. Each of these gases produces a different response mechanism consisting of protonation, deprotonation, reduction, swelling, and conformational alignment, respectively. The high surface area, small diameter, and porous nature of the nanofiber films allow for facile diffusion of vapors, which is responsible for the enhanced performance. Most recently we have shown that additives can also be incorporated in the polyaniline matrix to detect analytes that do not give a significant response with unmodified polyaniline. Fluoroalcohol additives can be used for enhanced hydrazine detection and hydrogen sulfide can be detected using polyaniline nanofibers modified with metal salt additives. Therefore polyaniline nanofibers appear to be superior and versatile chemical sensor materials that have excellent potential for many chemical detection applications including homeland security.
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Nanotech 2005 Conference Program Abstract