NIRT: Experimental and Theoretical Investigations of Aqueous Geochemical Interfaces - The Role of Nanoscale and Molecular Structures in Dictating Environmental Reactivity

本提案的重点是跨学科的方法来研究氧化铁表面结构和反应性的分子和纳米尺度。建议活动的智力价值：这里提出的研究将利用最先进的实验和理论方法来提供关于氧化铁反应性基本控制的独特信息。使用单晶基质和赤铁矿纳米颗粒复合材料的实验将用于确定污染物金属离子吸附的反应性趋势，以及这些随表面取向、表面质量和与“表面修饰物质”的反应如何变化。所提议的技术的互补性将使多种调查途径能够在连贯和协同的努力中进行，与分离的独立研究相比，将使人们更好地了解所调查的系统。该方法还充分利用了同步加速器表面结构技术和周期性从头算方法的最新进展，克服了目前纳米级颗粒原位表面结构研究的局限性。这项工作的主要贡献之一将是解释分子尺度表面结构和纳米尺度表面形貌/缺陷密度方面的反应性趋势。这将允许缩放的重要问题得到解决，因为随着颗粒尺寸减小到纳米尺度，表面缺陷对反应性的影响预计会急剧增加。这个研究小组特别有资格进行跨学科合作，目的是获得与环境界面化学有关的矿物表面结构和反应性的基本信息。所提出的活性的更广泛影响：纳米级固/水溶液界面的化学过程对环境化学和地球化学以及依赖于表面反应的各种技术领域（如多相催化和腐蚀控制）具有深远的影响。这里提出的工作将导致对金属离子在矿物表面的隔离（和从）释放的预测的改进，这将最终导致用于评估污染物风险和设计污染物补救策略的定量模型的改进。在追求该项目的技术目标的同时，主要的重点将放在为本科生、研究生和博士后学生提供教育机会上。学生参与者将参与该项目的各个方面，从而提供同步加速器实验，从头算电子结构计算和分析实验室实践的研究经验。因此，该项目的主要影响之一将是培养下一代科学家，包括妇女和少数民族，他们在分子环境科学的理论和技术方面受过良好的训练，这是高度跨学科的，由于环境系统的复杂性，在理解基本化学过程方面提出了重大挑战。这项工作的其他教育影响将反映在成员机构的设施和专门知识的发展，以及通过同行审查的出版物和报告向更广泛的科学界和一般社会传播结果。

0404400TrainorThe focus of this proposal is an interdisciplinary approach to molecular and nanoscale investigations of iron-oxide surface structure and reactivity. Intellectual merit of the proposed activity: The research proposed here will utilize state-of-the-art experimental and theoretical methods to provide unique information about the fundamental controls on reactivity of iron-oxides. Experiments using both single crystal substrates and nanoparticle composites of hematite will be used to determine reactivity trends with respect to adsorption of contaminant metal ions, and how these vary with surface orientation, surface quality, and reaction with "surface modifying species". The complementary nature of the proposed techniques will allow multiple avenues of investigation to be pursued in a coherent and synergistic effort and will result in a better understanding of the systems under investigation as compared with decoupled, independent studies. The proposed methodology also overcomes current limitations on in-situ surface structural studies of nanoscale particles by taking full advantage of recent advances in synchrotron-based surface structural techniques and periodic ab-initio methods. One of the main contributions of this work will be to explain reactivity trends in terms of molecular scale surface structure and nanoscale surface topography/defect density. This will allow the important question of scaling to be addressed since the effects of surface defects on reactivity are anticipated to increase dramatically as particle size decreases to the nanometer scale. This research team is particularly well qualified for an interdisciplinary collaboration aimed at obtaining fundamental information on mineral surface structure and reactivity relevant to the environmental interface chemistry.Broader impacts of the proposed activity: Chemical processes at nanoscale solid/aqueous solution interfaces have far-reaching impacts in environmental chemistry and geochemistry, as well as in various areas of technology that depend on surface reactions, such as heterogeneous catalysis and corrosion control. The work proposed here will lead to improved predictions about metal ion sequestration on (and release from) mineral surfaces, which will ultimately lead to improvements in quantitative models used for assessment of contaminant risk and the design of contaminant remediation strategies. While pursing the technical goals of this project, a major emphasis will be placed on providing educational opportunities to undergraduate, graduate, and post-doctoral students. Student participants will be involved in all aspects of this project, thereby providing research experience in synchrotron-based experimentation, ab-initio electronic structure calculations, and analytical laboratory practices. Thus one of the main impacts of this project will be to produce the next generation of scientists, including women and minorities, who are well trained in the theory and techniques of molecular environmental science, which is highly interdisciplinary and presents major challenges in terms of understanding fundamental chemical processes due to the complexity of environmental systems. Additional educational impact of this work will be reflected in the development of facilities and expertise at the member institutions and by dissemination of results to the broader scientific and general community through peer reviewed publications and presentations.