Date of Award

6-2003

Document Type

Union College Only

Degree Name

Bachelor of Science

Department

Chemistry

Language

English

Abstract

I have developed gas sensors that respond rapidly and noticeably to changes in oxygen concentration by doping fluorescent complexes into gas-permeable sol-gel materials. Ruthenium (II) 4,7-diphenyl-1,10- phenanthroline, Ru(dpp)32+, responds to variations in ambient oxygen concentrations through marked changes in its fluorescence intensity. I investigated the response of Ru(dpp)32+ to oxygen in solution, in aerogels (sol gels dried under ambient conditions) and in aerogels (sol gels dried using supercritical conditions). Aerogels have particularly high porosity and low density, which allows for rapid diffusion of gases into the material. The aerogel sensor responds reversibly to changes in ambient oxygen concentration within 10 s, as compared to 50 s for Ru(dpp)32+ in a aerogel and a 69-min. response time in solution. These rapid, reversible systems have potential for use as switches, and future work will focus on evaluating their use as quantitative oxygen sensors. In addition, I have conducted fluorescence lifetime measurements to monitor probe partitioning within the aerogels and aerogels, in order to ascertain whether there are fundamental differences in the microenvironments experienced by the probes in the two types of sol gels. I have found that the probes exist in two distinct microenvironments (presumably, within the silicate matrix and along the pore-matrix interface region) within both types of sol-gel materials. This indicates that probe partitioning likely occurs early on in the sol-gelation process.

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