RUI: Influence of Surface Interactions of Organic Ligand-Iron Oxide/Water Interfaces on Carbon and Iron Cycling Studied by Second Harmonic and Sum Frequency Generation Spectroscopy

在化学系环境化学科学项目的支持下，普吉特海湾大学的阿曼达米夫林博士和本科研究人员正在利用表面特异性激光技术探索有机配体与氧化铁矿物表面之间的相互作用。他们的实验研究得到了与太平洋西北国家实验室（PNNL）分子科学计算组科学家合作进行的计算建模的补充。所研究的系统作为土壤中常见的地球化学系统的模型，对理解元素（或其化合物）在生命系统和环境之间转移的过程具有重要意义。 该项目特别考虑了植物和动物以及土壤和河流中铁和碳的转移。 这项研究为本科生提供了发展关键技术和沟通技能的机会，为他们成功的职业生涯做好准备。他们在PNNL的时间向他们展示了政府实验室的职业道路。 他们在区域性场所的演讲也有助于向公众宣传环境问题。在环境相关浓度下直接测量金属表面络合物，特别是那些涉及与有机配体表面络合机理的表面络合物，是很难研究的。 Mifflin小组正在使用二次谐波产生（SHG）和和频率产生（SFG）探测矿物氧化物/含水有机体系，以获得金属络合物表面性质和结合过程的分子水平信息。 研究人员寻求在环境相关条件下更全面地了解这些系统的结合和氧化还原化学。具体而言，吸附，解吸和溶解行为的含水铁载体desferrioxamine-B（DFO-B）在赤铁矿/水界面正在研究作为一个模型的有机-矿物地球化学系统中常见的土壤。计算研究有助于解释实验结果，针对其他矿物表面-有机配体相互作用的预测能力。实验提供了表面覆盖，结构和动力学的络合和溶解，和分子取向的直接光谱证据。 这些关于地球化学铁和碳循环的信息反过来又可以改进全球模型。

With support from the Environmental Chemical Sciences Program of the Division of Chemistry, Dr. Amanda Mifflin and undergraduate researchers at the University of Puget Sound are probing the interactions between organic ligands and the surfaces of iron oxide minerals using surface-specific laser techniques. Their experimental studies are complemented by computational modeling carried out in collaboration with scientists in the Molecular Science Computing group at Pacific Northwest National Laboratory (PNNL). The systems under study serve as models for geochemical systems commonly found in soils, and have important implications for understanding the process by which elements (or their chemical compounds) are transferred between living systems and the environment. This project specifically considers the transfer of iron and carbon from plants and animals and the soil and streams. The research provides undergraduate students with opportunities to develop critical technical and communication skills that prepare them for successful careers. Their time at PNNL shows them career paths to government laboratories. Their presentations in regional venues also help inform the general public about environmental issues.Direct surface measurements of metal-surface complexes at environmentally relevant concentrations, especially those involving the mechanisms of surface complexation with organic ligands, are difficult to study. The Mifflin group is probing mineral oxide/aqueous organic systems using second harmonic generation (SHG) and sum frequency generation (SFG) to gain molecular-level information of the surface properties and binding processes of metal complexes. The researchers seek a more complete understanding of the binding and redox chemistry of these systems under environmentally relevant conditions. Specifically, the adsorption, desorption and dissolution behavior of the aqueous siderophore desferrioxamine-B (DFO-B) at the hematite/water interface is being studied as a model for organic-mineral geochemical systems commonly found in soils. The computational studies aid in the interpretation of experimental results, targeting predictive capability for other mineral surface-organic ligand interactions. The experiments provide direct spectroscopic evidence of surface coverage, structure and kinetics of complexation and dissolution, and molecular orientation. This information about biogeochemical iron and carbon cycling can in turn lead to improved global models.