Single Molecule Fluorescent Indicators for Gas-Phase Sensing of Metals

重金属通过自然和人类活动源源不断地进入大气，这一过程危及公众的健康和福祉以及环境。目前测量大气中有害金属存在的方法需要耗时的过程来浓缩金属靶材，以及复杂的分析所需的复杂的样品制备方法。这些现有方法的一个主要局限性是，大气物质必须放在水或其他溶剂中进行分析。通过对气体生成时(进入大气层之前)气体中存在的金属进行直接光测量，可以在快速检测重金属方面取得重大进展。然而，由于无法研究感兴趣的金属与报告金属存在的荧光受体之间的分子水平相互作用，我们对如何使用荧光光传感器检测气体中重金属的理解受到阻碍。单分子荧光成像技术可能会改进重金属离子气相传感器的设计。这些使能技术有可能提供金属污染的早期检测，以帮助防止对人类健康和环境造成重大损害。德克萨斯大学阿灵顿分校最近在气体离子的单一实体荧光成像方面取得了进展。该项目将独特的技术结合在一起，创造出测量有毒重金属的灵敏气相传感器，重点放在铅、汞和镉作为一些最有害的重金属。S博士的研究生、本科生和高中研究人员在实验室设计和制造复杂的荧光成像材料，放置在光学表面上。然后，这些材料可以用来评估大气中是否存在金属。研究和培训环境允许学习分子的基础知识-金属化学、光物理和制造分子的尖端方法，以及推动科学家在培训中的职业生涯的科学素养和团队合作技能。他在德克萨斯大学阿灵顿分校从事合成和研究杂化材料的工作，该材料直接研究重金属离子捕获、表面动力学和气固界面荧光的基本原理。基本的动力学和热力学性质因分析物在无溶剂环境中结合的似乎不可逆性而变得复杂，并受到研究表面离子整体性质的方法的限制，而不是分子性质的研究。开启的单分子荧光成像(SMFI)方法彻底改变了我们对溶液中分子水平上的生物分子和催化事件的理解。含有刚性离子选择受体和固态功能荧光团的新型开启荧光传感器的制备提供了SMFI材料，这些材料可以被结合到气固界面的自组装单分子膜中。为了提高离子结合的选择性，用固体电解质激发的离子传输材料对SMFI-SAM进行了修饰。SMFI-SE-SAM中的离子传感和迁移率测量由显微镜进行研究，并以计算实验为支持，以增强气相传感技术，并为研究表面设计和功能提供新的工具。这些研究提供了通过快速气敏荧光测量实现超低水平检测所必需的分子尺度洞察力。这一跨学科合作项目将新材料与最近开发的显微技术结合在一起，以评估这些设备直接从气相中检测有毒重金属离子的测量和选择性。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.