Olefins at the Surfaces of Transparent Oxides Studied With Coherent Vibrational Spectroscopy

0931701 geiger本奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。该建议侧重于实验室测量，旨在阐明催化相关碳氢化合物在氧化物表面的分子取向。PI将确定与SiO2， Al2O3和相关氧化物（C2至C6衍生物以及喹嘌呤衍生物）的异相催化相关的常见饱和和不饱和手性和非手性烃的分子取向和分布，方法是在CH拉伸区使用振动和频率生成来分配它们的振动表面光谱。他将开发一种振动模式分配策略，用于从SFG光谱中确定给定振动模式的对称性，使他们能够识别给定模式是对称的还是不对称的。这一策略将极大地促进在催化相关氧化物上的催化相关烃类的振动光谱分析和分子取向和结构的确定。知识价值：无机和有机物质在金属和金属氧化物上的反应在非均相催化中受到了广泛的关注，并在2007年获得了诺贝尔化学奖。该领域最近的主要进展之一是，现在人们已经认识到，在非均相催化中，吸附有机物质的分子取向对控制界面反应活性和动力学至关重要。虽然在了解与催化相关的金属底物的反应性和动力学方面已经开展了大量工作，但关注碳氢化合物与催化相关氧化物相互作用的振动研究较少，而且往往不关注于确定碳氢化合物在催化相关表面上的分子取向。此外，虽然C-H拉伸频率区信息含量丰富，但由于频谱拥挤，难以用标准振动光谱进行解释。这两个问题都可以通过利用表面选择性和振动和频率产生的相干性来克服。由于缺乏对氧化物表面吸附的大多数催化相关碳氢化合物的彻底分配的振动光谱，PI将其他碳氢化合物的开创性表面光谱实验从金属表面扩展到氧化物表面。更广泛的影响：科学界，特别是从事多相催化研究的科学家，将受益于有关烯烃和相关催化相关分子的结构和取向的分子水平信息的改进。这项工作的光谱和结构数据将使该领域的其他科学家能够完善化学和机制模型，用于描述固体/气体界面上重要的催化非均相过程，获得氧化物表面有机化合物分子取向的分子水平信息，从理论计算中获得光谱和结构数据的基准，并提高预测催化活性的准确性。这一建议扩大了对多相催化的基本分子水平的理解。它还将使自然界中发现的界面现象的现有理论和机制框架取得进展。通过直接或间接地与学生和政策制定者互动，PI的综合研究、教育和公众宣传活动将继续成为向公众传播科学成果的有力工具。

0931701 GeigerThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This proposal focuses on laboratory measurements aimed at elucidating the molecular orientation of catalytically relevant hydrocarbons at oxide surfaces. The PI will determine the molecular orientation and distributions of common saturated and unsaturated chiral and achiral hydrocarbons relevant to heterogeneous catalysis (C2 through C6 derivatives as well as quinuclidine derivatives) on SiO2, Al2O3, and related oxides by assigning their vibrational surface spectra using vibrational sum frequency generation in the CH stretching region. He will develop a vibrational mode assignment strategy for determining the symmetry of a given vibrational mode from SFG spectra, allowing them to identify whether a given mode is symmetric or asymmetric. This strategy will greatly facilitate the analysis of the vibrational spectra and molecular orientation and structure determination of catalytically relevant hydrocarbon species at catalytically relevant oxides.Intellectual Merit: Reactions of inorganic and organic species on metals and metal oxides have received much attention in heterogeneous catalysis, culminating in the 2007 Nobel Prize in chemistry. One of the major recent advances in the field is that it is now understood that the molecular orientations of the adsorbed organic species are critical for controlling interfacial reactivity and kinetics in heterogeneous catalysis. While much work has been carried out on understanding reactivity and kinetics on metal substrates relevant to catalysis, vibrational studies focusing on the interaction of hydrocarbons with catalytically relevant oxides are sparser and tend not to focus on determining the molecular orientations of the hydrocarbon species at the catalytically relevant surface. Furthermore, while the C-H stretching frequency region is rich in information content, it is difficult to interpret using standard vibrational spectroscopy due to spectral congestion. Both issues are overcome by taking advantage of the surface selectivity and the coherent nature of vibrational sum frequency generation. Motivated by the lack of thoroughly assigned vibrational spectra for most catalytically relevant hydrocarbons adsorbed to oxide surfaces, the PI extends the pioneering surface spectroscopy experiments on hydrocarbons of others from metal surfaces towards oxide surfaces.Broader Impacts: The scientific community, especially scientists working on heterogeneous catalysis, will benefit from improved molecular-level information regarding the structure and orientation of olefins and related catalytically relevant molecules. The spectroscopic and structural data from this work will allow other scientists in the field to refine chemical and mechanistic models for describing catalytically important heterogeneous processes at solid/gas interfaces, obtain molecular-level information on the molecular orientation of organic compounds at oxide surfaces, benchmark their spectroscopic and structural data from theory calculations, and improve the accuracy in predicting catalytic activity. This proposal expands the fundamental molecular-level understanding of heterogeneous catalysis. It will also enable advances of existing theoretical and mechanistic frameworks for interfacial phenomena found in nature. By directly and indirectly interacting with students and policy makers, the PI's integrated research, education, and public outreach activities will continue to be powerful tools for communicating scientific efforts to the general public.