| The goal of research described in this thesis has been to develop novel chemical sensors using porous optical fibers.; A porous glass optical fiber has been developed by heat treating a borosilicate glass fiber to promote phase separation. Subsequent leaching out of the boron-rich phase produces an interconnected porous structure with high surface area. Absorption of light passing through the porous glass segment results in chemical sensors which have a much higher sensitivity than others which rely on evanescent waves principles of operation. The utilization of optical indicators in conjunction with the porous glass optical fiber has resulted in the development of humidity, ammonia, and pH sensors with enhanced sensitivity detection. Sensor parameters such as sensitivity range, response time, stability, and temperature effects have also been investigated.; A unique approach for fiber optic chemical sensors using a porous polymer optical fiber was also developed. The porous polymer optical fiber is made by a heterogeneous copolymerization technique. The experiments have shown that the porous polymer optical fiber demonstrates the high sensitivity similar to the porous glass fiber, but it also has high gas permeability and liquid impermeability. This makes the fiber serve both as a transducer and gas selective membrane. A sensor based on this fiber has been developed to measure the concentration of ammonia in aqueous solutions. This porous polymer fiber was also utilized to develop a carbon monoxide probe capable of in-line monitoring.; The response time, calibration curves, and temperature effects for these sensors were modeled from fundamental concepts involving both thermodynamic and diffusion kinetics of the sensing probes. The modeling provides some valuable information and insight from which future generation sensor probes can be designed. |
