Heavy metals are continuously introduced into the atmosphere by natural and human activity, a process that endangers the health and well-being of the public and the environment. Current methods for measuring the presence of harmful metals in materials in the atmosphere require time-consuming processes to concentrate metal targets, as well as complicated sample preparation methods for the intricate analyses. A major limitation of these existing methods is that atmospheric materials have to be placed in water or other solvents to be analyzed. Significant advances in rapid, heavy metal detection could occur by direct light-based measurement of metals present in gases at the point of their generation (prior to entering the atmosphere). However, our understanding of how to detect heavy metals in gases using fluorescent light-based sensors is hindered by the inability to study molecular-level interactions between a metal of interest and fluorescent receptors that report metal presence. Single-molecule fluorescence imaging technologies may enhance the design of gas-phase sensors for heavy metal ions. These enabling technologies have the potential to offer early-stage detection of metal contamination to help prevent significant harm to human health and the environment. Recent advances in the single-entity fluorescence imaging of ions from gases have been made at the University of Texas at Arlington. This project brings together a unique combination of techniques to create sensitive gas-phase sensors that measure toxic heavy metals, with a focus on lead, mercury, and cadmium as some of the most harmful heavy metals. Graduate, undergraduate, and high school researchers in Dr. Frank Foss Jr.’s laboratory design and make sophisticated fluorescence imaging materials that are placed on optical surfaces. These materials can then be used to assess presence of metals in the atmosphere. The research and training environment allows for learning about fundamentals of molecule-metal chemistry, photophysics, and cutting-edge approaches to making molecules, as well as scientific literacy and teamwork skills that propel the careers of the scientists in training.

With this award, the Chemical Measurement and Imaging Program is funding Dr. Frank Foss Jr. at the University of Texas at Arlington to synthesize and study hybrid materials that directly investigate the fundamentals of heavy metal ion capture, surface dynamics, and fluorescence at gas-solid interfaces. Fundamental kinetic and thermodynamic properties are complicated by the seemingly irreversible nature of analyte binding in solvent-less environments and limited by methods that investigate bulk properties of ions on surfaces, rather than molecular properties. Turn-on, single-molecule fluorescence imaging (SMFI) methods have revolutionized our understanding of biomolecular and catalytic events at the molecular level in solution. Preparation of new turn-on fluorescence sensors containing rigid ion-selective receptors with solid-state functioning fluorophores provide SMFI materials that can be incorporated into self-assembled monolayers at gas-solid interfaces. To enhance ion binding selectivity, SMFI-SAMs are modified with solid electrolyte-inspired ion transport materials. Ion sensing and mobility measurements in SMFI-SE-SAMs are studied by microscopy and supported by computational experiments to enhance gas-phase sensing technologies and provide new tools for investigating surface design and function. These studies provide the molecular scale insight necessary for attaining ultra-low levels of detection by rapid gas sensitive fluorescent measurements. This interdisciplinary collaborative project brings together new materials with recently developed microscopy techniques to evaluate the measurement and selectivity of these devices to detect toxic heavy metal ions directly from the gas phase.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

National Science Foundation (NSF)
Division of Chemistry (CHE)
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Robin McCarley
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University of Texas at Arlington
United States
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