Water Resources Research Act Program

Details for Project ID 2007CT130B

Development of a new generation of sensitive, fluorescence-based nitrate sensors for use in soil and water

Institute: Connecticut
Year Established: 2007 Start Date: 2007-09-01 End Date: 2009-08-31
Total Federal Funds: $63,662 Total Non-Federal Funds: $134,021

Principal Investigators: Shawn Burdette, Zoe Cardon

Project Summary: Our aim is to start development of a new generation of nitrate sensor for use in soil solution or in freshwater. Connecticut has long had a strong focus on nitrogen-based contaminants in groundwater, surface water, and ultimately, Long Island Sound. The development of this sensor would be particularly helpful in monitoring efforts where persistent low levels of nitrate, not extremely high concentrations (e.g. sewage plant emissions), need to be measured. For a year now, Cardon has been discussing the nitrogen contamination problems in Connecticut with representatives from United States Geological Survey and the Connecticut Department of Environmental Protection, and last fall, she invited Paul Stacey and John Mullaney to mentor and lecture to a graduate level course in the Center for Integrative Geosciences focusing explicitly on non-point sources of groundwater nitrate contamination in Connecticut and Long Island Sound. Interest in monitoring nitrate in soil solution and freshwaters is immediate, and although there are nitrate sensors on the market currently, their sensitivity is geared toward hot spots such as plumes of contaminated water flowing from sewage treatment plants or from agricultural waste. A sensitive, relatively inexpensive, and miniaturized nitrate sensor is sorely needed by the monitoring, ecological, and environmental engineering communities. Burdette joined the faculty of the University of Connecticut chemistry department last year, and brings expertise in development of selective, fluorescence-based chemical sensors. Working together, Burdette and Cardon have the expertise to design, prepare and develop more sensitive nitrate sensors for use in soils and freshwaters that emphasize sensitivity in the range of 0-3 mg per liter found in many uncontaminated local waters in New England and around the United States. Fluorescent sensors are extremely useful chemical tools for measuring concentrations of metal ions, anions and small molecules in a variety of environments because of their sensitivity, ease of use, small size and low cost. Most importantly, miniature, inexpensive fluorescent sensors can be deployed in arrays over wide areas and monitored easily for extended periods of time. Although sensors exist for a variety of analytes, there are very few viable fluorescent sensors for nitrate available, and none has been developed to the point of commercialization. Because of its unique chemical properties, binding and detecting nitrate represents a significant challenge. To address these issues, several strategies for engineering dendrimer-based sensors have been proposed. Dendrimers are particularly amenable to environmental sensing applications because of their robust structures (making them reusable) and ease of synthesis. All three strategies rely on binding and accumulation the negatively charge nitrate to generate a fluorescence response. In the first strategy, negative charge induces an isomerization of a fluorophore from a non-emissive to fluorescent form; the second, involves nitrate displacing quenching ions from dendrimer cores; and in the third, coupling dendrimer swelling to changes in fluorescence resonance energy transfer (FRET) between two fluorescent molecules. Each sensor system takes advantage of nitrate receptors designed to bind nitrate selectively in the presence of other anions present in nature. While the initial stage of the research project will address basic sensor design and detection strategy, the ultimate goal is integrate these molecular sensors into user-friendly devices that can be used by members of the ecological and environmental science communities.