Date of Award
Union College Only
Bachelor of Science
The purpose of this research was to develop a fiber-optic sensor for sulfite via immobilizing Methylene Blue (MB) within a sol-gel matrix. MB is a redox-indicating dye. In the oxidized form, the dye is a blue color, but reduction causes a change to the colorless, leuco form. This property is advantageous for the detection of reducing agents, such as sulfite. In solution, leuco-MB reverts to its blue form in the presence of an oxidizing agent. The method of MB immobilization is through the use of sol gels. The environment of a sol gel is chemically inert and small analytes can easily diffuse into a thin-film matrix. In this study, the sol-gel matrix was formed via the hydrolysis and polycondensation of tetraethoxysilane (TEOS) as well as organically-modified orthosilicates. Blue MB is converted to leuco-MB in both solution and in the thin-film coated fiber upon exposure to sulfite. In the sol gel, however, blue-MB is not regenerated in the presence of oxidizing agents. Hence, the sensor cannot be regenerated and is currently only satisfactory for a single use. Fundamental studies of the spectroscopic properties, including absorbance and fluorescence spectra, of the sol gel environment were also performed as the sol gel aged.
Morcone, Tara K., "The characterization of methylene-blue-doped sol gels and the development of a fluorenscence-based fiber-optic sensor for sulfite" (1999). Honors Theses. 2071.