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Published April 1, 2003 | public
Journal Article

Enhanced Sensitivity to and Classification of Volatile Carboxylic Acids Using Arrays of Linear Poly(ethylenimine)−Carbon Black Composite Vapor Detectors


Vapor detectors formed from composites of conductors and insulating organic polymers have been tailored to produce increased sensitivity toward specific classes of analyte vapors. Upon exposure to acetic acid at 1% of its vapor pressure, detectors consisting of linear poly(ethylenimine) (l-PEI)−carbon black composites showed an ∼10^3 increase in signal/noise relative to the performance of typical insulating organic polymer−carbon black composite vapor detectors. Compositional diversity in an array of such vapor detectors was obtained by varying the degree of plasticization of the l-PEI films. The resulting vapor detector array produced sensitive detection of, and robust discrimination between, various volatile organic acids and relatively little response from nonacidic organic vapors or from water vapor. Measurements of the mass uptake, thickness change, and electrical conductivity of such composites indicate that swelling of the polymer film, and thus its normalized resistance response, is beyond that expected by mass uptake alone upon exposure to acetic acid vapor. This additional thickness increase is attributed to charge-induced polymer swelling occurring from polymer−analyte interactions. Electrical percolation also plays a significant role in producing the large increase in normalized resistance response of these composites upon exposure to acetic acid vapor.

Additional Information

© 2003 American Chemical Society. Received 24 June 2002; accepted 6 November 2002; published online 1 March 2003; published in print 1 April 2003. We acknowledge the NIH and an ARO MURI for support of this work.

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