Ballantine, David Stephen
M.S. (Master of Science)
Department of Chemistry
Optical wave guides; Vapors; Chemical detectors
A chemical sensor is an electronic device which is designed to produce a measurable signal in response to some chemical stimulus. Because of federal regulations regarding workers' safety and increased costs in healthcare, there has been much interest in monitoring hazardous chemicals in the workplace. Chemical sensors are well suited for this purpose because of their small size, portability, low power requirements, and relatively low cost. Sensing devices that are seeing widespread development include piezoelectric, electrochemical, and optical devices. Because of their flexible geometry, immunity to electromagnetic interference, and ability to channel light over long distances, optical waveguides (OWG) are well suited for remote sensing of hazardous environments. An OWG consists of a medium of core material surrounded by a cladding of lower refractive index material. The difference in refractive index between the two materials allows light entering the waveguide at an angle greater than the critical angle to travel down the waveguide through a series of multiple internal reflections. If the waveguide is coated with a reagent that undergoes a change in its optical properties upon exposure to a chemical stimulus, the waveguide serves as a chemical sensor. The purpose of this work was to develop an OWG sensor for the detection of acidic and alkalescent vapors. Limits of detection for HCl(g), H 2 S (g), and N H 3 (g) were 10 ppb, 15 ppm, and 78 ppm respectively. Water acted as a system interferent by increasing the transmittance of the waveguide, and as a chemical interferent by decreasing the response of the sensor to HC1 while increasing sensor response to NH[sub]3 .
Callahan, Daniel J., "Development of an optical waveguide sensor for the detection of acidic and alkalescent vapors" (1992). Graduate Research Theses & Dissertations. 2185.
vii, 86 pages
Northern Illinois University
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