Electron Transfer Mediators at Environmental Interfaces

化学系的环境化学科学项目正在资助俄勒冈健康科学大学的Paul G. Tratnyek教授，研究被称为“电子穿梭体”的物质如何在环境中固溶体表面介导氧化还原反应的基础和应用方面。氧化还原（氧化还原）反应是环境化学许多最重要方面的组成部分，从元素循环到微生物燃料电池，再到污染物的命运和修复。众所周知，许多氧化还原过程受到自然和人工电子穿梭的强烈影响，但界面在电子穿梭效应中的作用很难表征，也很难理解。除了由研究生、本科生和高中实习生进行的实验室研究外，该项目还包括Clackamas社区学院为水行业专业人士举办的研讨会。这些讲习班的一个目标是更好地了解和利用氧化还原穿梭效应保护安全饮用水。这个项目的方法是使用电极作为环境接口的模型系统。电极以各种方式修饰电子穿梭化合物，然后使用电化学仪器测量氧化还原过程。项目范围包括不同类型的电极材料（例如，贵金属与氧化铁矿物），穿梭电极相互作用（例如，键合与非键合），以及穿梭类型（醌类，黄酮类，卟啉类，铁载体等）。将使用基于电极的模型系统研究界面对ETM性能的影响，该系统可以系统地表征ETM的界面结构和反应性。电极模型系统将用于表示三种类型的场景：(i)仅溶液相ETM效应，与ETM界面相互作用（ii）非特异性和非键合（即外球）或（iii）特异性和键合(即？内球体吗?)表面将包括由玻璃碳和金制成的电极（分别隔离外部和内部球体的相互作用）和生长在金属铁电极上的氧化铁（代表环境矿物表面）。etm将从四类对环境重要的氧化还原活性有机物中选择：醌类、黄素类、卟啉类和铁载体。每个系统将主要通过循环伏安法（CV）和电化学阻抗谱（EIS）进行电化学表征。补充光谱方法将根据需要应用：包括UV-vis， FTIR，表面等离子体共振（SPR）光谱。定量结果（电位、电流、阻抗）将用于推导界面etm的性质，并将这些结果与使用各种方法（实验和计算）确定的溶液相etm的值进行比较。总体结果将用于评估界面效应对环境氧化还原性能的总体意义。

With this award, the Environmental Chemical Sciences Program in the Division of Chemistry is funding Professor Paul G. Tratnyek of the Oregon Health & Science University to investigate fundamental and applied aspects of how substances termed "electron shuttles" mediate redox reactions at solid-solution surfaces in the environment. Redox (oxidation-reduction) reactions are integral to many of the most important aspects of environmental chemistry, ranging from elemental cycling, to microbial fuel cells, to contaminant fate and remediation. Many of these redox processes are known to be strongly influenced by natural and artificial electron shuttles, but the role of interfaces in electron shuttle effects is hard to characterize and poorly understood. In additional to the laboratory research performed by graduate students, undergraduates, and high school interns, this project includes significant outreach activity with workshops for water industry professionals run by Clackamas Community College. One goal of these workshops is to better understand and utilize redox shuttle effects in the protection of safe drinking water.The approach of this project is to use electrodes as model systems for environmental interfaces. Electrodes are modified in various ways with electron shuttle compounds followed by measurement of redox processes using electrochemical instrumentation. The project scope includes different types of electrode materials (e.g., noble metals vs. iron oxide minerals), shuttle-electrode interactions (e.g., bonded vs. non-bonded), and shuttle types (quinones, flavins, porphyrins, siderophores, etc.). Interfacial effects on ETM properties will be studied using electrode-based model systems that allow systematic characterization of ETM-interface structure and reactivity. Electrode model systems will be used to represent three types of scenarios: (i) solution phase ETM effects only, vs. ETM-interfaceinteractions that are (ii) non-specific and non-bonded (i.e., ?outer-sphere?) or (iii) specific and bonded (i.e., ?inner sphere?). The surfaces will include electrodes made of glass carbon and gold (to isolate outer and inner-sphere interactions, respectively) and iron oxides grown on metallic iron electrodes (to represent environmental mineral surfaces). ETMs will be selected from four classes of environmentally important redox-active organics: quinones, flavins, porphyrins, and siderophores. Each system will be characterized electrochemically, primarily by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Complementary spectroscopic methods will be applied as needed: including UV-vis, FTIR, surface plasmon resonance (SPR) spectroscopy. Quantitative results (potential, current, impedance) will be used to derive properties of interfacial ETMs and these will be compared to values determined for solution-phase ETMs using various methods (experimental and computational). The overall results will be used to assess the overall significance of interfacial effects on environmental redox properties.