Date of Award

6-2003

Document Type

Union College Only

Degree Name

Bachelor of Science

Department

Chemistry

Language

English

Abstract

A sol-gel is a silicon-oxygen matrix that is suitable for the entrapment of chemical species, including biological species, indicators, dyes, and sensors. Aerogels are sol-gels prepared by supercritical extraction, whereas aerogels are allowed to dry under ambient conditions. The resulting materials differ considerably in their physical properties. We are investigating a series of luminescent species for use as probes of the microenvironment in different sol-gel materials. Sol gels containing each probe are prepared as both aerogels and aerogels; aerogels are formed using a novel contained mold process. Spectral properties, including absorption or excitation spectra, emission spectra, time-based fluorescence scans, and fluorescence lifetime, of the entrapped probes are measured. The research focuses on two dyes, tris(2,2'-bipyridyl}ruthenium(ll) , an oxygen sensor referred to as Ru(bpy)32+, and Eosin-Y, a pH-indicator. Eosin-Y is successfully entrapped in aerogels and can be used to differentiate between aerogel materials, but does not survive the aerogel formation process. The response times of Eosin-Y-doped aerogels and pin-printed sol-gel microsensors to changes in pH are also investigated. The doped aerogels have relatively long response times of 20 minutes. Microsensors are expected to have shorter response times. Aerogels and aerogels doped with Ru(bpy)32+ have similar excitation spectra, with maxima at 470 nm, with aerogels having enhanced intensity. The Ru(bpy)32+ doped materials differ in t:Je shape of their emission bands, with emission maxima ranging from 590 to 604 nm. Lifetime data for aerogels and aerogels doped with Ru(bpy)32+ differ indicating that the species is entrapped in different microenvironments. Ru(bpy)32+ -doped aerogels are successfully used as oxygen sensors and demonstrate response times of approximately 3 seconds.

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