Project 6. Structure and Properties of Metal Oxide Particle-Adsorbate Systems

环境持久性自由基(EPFR)是当分子吸附在过渡金属氧化物表面时形成的。电子从分子到金属的转移导致金属的还原和有机分子吸附上的自旋密度的产生，即EPFR的形成。这些“界面污染物”相对稳定(即持续数小时或数天)，因此它们可以进入环境，对健康造成有害影响。此外，这些系统在超级基金地点特别普遍，因此有必要对它们进行研究和表征，以了解它们在超级基金地点附近对人类健康影响中的作用。然而，这些系统是复杂的，很难表征，所以我们设计了这个项目，以了解导致它们产生的详细的结构和化学转化。具体地说，该项目主要使用X射线光谱分析和透射电子显微镜分析来探索这些颗粒结合污染物的物理和化学特征。有三个具体的目标：(1)开发可控、可重复地产生含有金属氧化物的纳米颗粒作为在真实环境中发现的纳米团簇的替代品，(2)从结构和电子角度表征金属纳米颗粒，以及(3)确定导致持久自由基和其他有毒污染物形成的CHC的表面过程和相互作用。本项目对粒子表面的电子性质进行了表征，这对其他项目是必不可少的。与项目1的合作将导致对EPFR的结构和电子性质的了解，这将使这些研究人员能够了解影响EPFR形成和反应性的因素。它为项目3中超级基金土壤中EPFR的研究提供了背景。它同样提供了必要的化学，以了解生物医学项目2、4和5中展示的吸入EPFR所引起的健康影响。最后，金属氧化物颗粒和表面结合分子的结构特征对于计算核心和材料核心都是必不可少的。

Environmentally persistent free radicals (EPFRs) are formed on surfaces of transition metal oxides when molecules chemisorb on them. Electron transfer from the molecule to the metal results in reduction of the metal and the creation of spin density on the organic molecular adsorbate, i.e., formation of the EPFR. These "interfacial pollutants" are relatively stable (i.e., persisting for hours or days), so they can enter the environment and have deleterious health effects. Moreover, these systems are particularly prevalent at Superfund sites, so it is essential that they be studied and characterized in order to understand their roles in human health impacts in the vicinity of Superfund sites. However, these systems are complex and difficult to characterize, so we have designed this project to understand the detailed structural and chemical transformations that are responsible for their creation. Specifically, this project explores the physical and chemical characteristics of these particle-bound pollutants primarily using x-ray spectroscopy and TEM analysis. There are three Specific Aims: (1) Develop methods for controlled, reproducible generation of metal oxide-containing nanoparticles as surrogates of nanoclusters found in real-world environments, (2) Characterize the metal nanoparticles, structurally and electronically, and (3) Determine the surface processes and interactions of CHCs that lead to the formation of persistent free radicals and other toxic pollutants. This project characterizes the electron properties of the particle surface, which is indispensable for the other projects. Collaboration with Project 1 will lead to understanding of the structure and electronic properties of the EPFRs, which will allow those researchers to understand the factors affecting EPFR formation and reactivity. It generates background for studies of EPFRs in Superfund soils in Project 3. It similarly provides the chemistry necessary to understand the health effects induced by inhalation of EPFRs demonstrated in biomedical projects 2, 4, and 5. Finally, the structural characterization of the metal oxide particles and the surface-bound molecules will be indispensable for both the Computational Core, as well as the Materials Core.