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Proceedings Paper

Infrared waveguide sensor with functionalized monolayer for detection of airborne pollutants
Author(s): David E. King; John D. Webb
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Paper Abstract

We report the development of a tubular infrared waveguide sensor incorporating a functionalized self-assembled monolayer (SAM) on its metallized interior surface. The SAM used in this application was 11-mercaptoundecanoic acid (MUA) assembled from a 5-mM solution in ethanol onto the inner surfaces of silvered PyrexR glass tubing (4-mm inside diameter by 21-cm length). The sensor was adapted with minor modifications to fit standard fiber-launching and detection optics, which incorporate a remote cryogenic detector and mate to a Fourier transform infrared (FTIR) spectrophotometer. The f1.5 optics allow a sufficient number of multiple reflections inside the sensor to achieve spectroscopic sensitivity to the SAM within a 15 minute measurement time at 2 cm-1 resolution. The overall optical configuration is similar to that of the waveguides used for gas chromatography (GC)-FTIR spectroscopy, except that the inner surface of the sensor, rather than the gas contained in the GC-FTIR waveguide, is sampled. After the FTIR spectrum of a freshly prepared sensor is recorded, the inner surface (functionalized with carboxylic acid) is exposed to an ambient or flowing atmosphere. The terminal acid groups exposed at the surface of the MUA SAM react with basic pollutants, such as amines, which can be indoor air pollutants. The spectrum of the exposed sensor is then recorded and ratioed to the original sensor spectrum to produce an absorbance spectrum characteristic of the reacted, surface-bound pollutant. Our sensor exhibited sensitivity to 15 ppm of octylamine in an ambient atmosphere after 2 hours of exposure at 36 degrees Celsius.

Paper Details

Date Published: 10 December 1996
PDF: 12 pages
Proc. SPIE 2836, Chemical, Biochemical, and Environmental Fiber Sensors VIII, (10 December 1996); doi: 10.1117/12.260611
Show Author Affiliations
David E. King, National Renewable Energy Lab. (United States)
John D. Webb, National Renewable Energy Lab. (United States)

Published in SPIE Proceedings Vol. 2836:
Chemical, Biochemical, and Environmental Fiber Sensors VIII
Robert A. Lieberman, Editor(s)

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