| DESCRIPTIONS OF POTENTIAL PROJECTS |
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Two Projects: Environmental Chemical Sensors High-performance (i.e., sensitive, accurate, and specific), inexpensive sensors for aquatic environmental monitoring networks are required in a wide range of disciplines, ranging from groundwater remediation (e.g., chlorinated alkenes and pesticide residues as analytes) to studying the phosphorus cycle (e.g., phosphate, phosphite, and hypophosphite as analytes). Progress in these fields largely is hampered by the lack of appropriate instruments. The approach requires probes that accommodate two functions: (1) specific recognition of the target chemical species; (2) transduction of the recognition event into a quantitative response signal. We are developing highly-sensitive fluorescent probes to selectively detect two important types of environmentally important analytes: halogenated alkenes and low-valent phosphorus compounds. The probe-analyte interaction needs to be specific and the probe’s functionality needs to be sufficiently perturbed to trigger the signaling part of the probe. Highly sensitive “reporter” probes have been designed to detect cations and anions quinones, specific antigens, NADH, and carbohydrates. Detection techniques that measure the signaling event triggered by molecular recognition include electrochemistry, vibrational (IR and Raman) spectroscopy, UV-visible absorption spectroscopy, and fluorescence spectroscopy. Fluorescence is among the most sensitive techniques for detecting small quantities of molecular substrates, and is often affected by binding of molecules or ions to the fluorescent system.
Project 1. Synthesis and spectroscopy of Ruthenium polypyridyl complexes with applications in environmental sensing
The interaction of alkene compounds with Ag(I) is well established, and we will take advantage of this interaction as the recognition function of a molecular recognition scheme. We will couple a Ag+ ion with a polypyridyl ruthenium(II) complex to function as a fluorescent reporter which undergoes a change in fluorescence behavior when the alkene forms a p-bonding interaction with the Ag(I). This project involves preparation of a series of complexes with a ruthenium(II) bipyridyl fluorescent reporter and a Ag(I) recognition unit linked by a p-delocalized (conjugated) acceptor ligand bridge (L) in the general form [(bpy)2Ru(L)Ag]3+. This series will have several properties that vary in a systematic fashion, controlled by changing the ligand L to increase the number of aromatic rings, and hence, the amount of delocalization of the excited state. The spectroscopic (ground and excited state absorption, fluorescence) properties and electrochemical behavior of the complexes will be measured, and the interaction of the Ru-L-Ag complex with a series of alkene compounds will be investigated. Project 2. Development of a field portable fluorescence lifetime spectrometer This project continues the ongoing development of a miniature, rugged, field-portable spectrometer for measurement of fluorescent lifetimes. We have designed the electronic and optical systems for a phase-correlation lifetime spectrometer, fabricated and assembled circuit boards for a first prototype, and are ready to begin debugging and testing of the system. The project will involve electronics testing and assembly, simple optical design, and some computer programming. This is an ideal project for someone with an electrical engineering or other electronics background who would like to gain experience in instrumentation development. |
