CAREER: Mapping the Chemical Reactivity of Metal Oxide Photocatalysts by Correlative Single-Molecule Fluorescence and Electron Microscopy

纳米晶光催化剂是一种微小的人造晶体，利用光来加速化学反应。只使用二氧化碳、水和阳光制造甲烷等燃料的光催化剂将对社会产生重大好处。然而，开发能够将阳光转化为燃料的光催化剂是一个具有挑战性的问题，需要对纳米晶体表面发生的化学反应有基本的了解。在美国国家科学基金会化学部大分子、超分子和纳米化学项目的支持下，圣路易斯华盛顿大学的Sadtler教授正在开发显微镜方法，以观察单个纳米晶光催化剂上发生的单个光驱动反应。Sadtler教授和他的学生一起对为什么纳米晶体表面的一些原子位置对催化特别活跃有了新的见解。萨德勒教授也将他的研究成果注入教育领域。他正在开发以原子结构和化学键为基础的新课程，教授化学和材料科学的前沿知识，并与圣路易斯地区的高中教师和学生合作。具有可调化学计量比的金属氧化物半导体纳米晶体是很有前途的光催化剂，可以通过太阳能分解水、部分甲烷氧化和二氧化碳还原来生产液体燃料。然而，单个催化剂颗粒之间特定的结构和形态特征对其整体活性的贡献还不是很清楚，因为每个颗粒都是不同的，并且具有不同的潜在反应位点。该项目使用超分辨率荧光显微镜和氧化还原活性荧光探针，以纳米级的空间分辨率监测单个金属氧化物纳米晶体上的光致电荷转移事件。对相同颗粒进行的反应性图谱与扫描电子显微镜的原子分辨率的关联揭示了单个颗粒中氧空位的分布如何影响其反应性。为了进一步发展金属氧化物光催化剂的结构-活性关系，将单分子、单粒子数据与甲烷氧化和二氧化碳还原的整体光催化活性的测量进行了比较。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nanocrystal photocatalysts are tiny, synthetic crystals that use light to accelerate chemical reactions. Photocatalysts that make fuels, such as methane, using only carbon dioxide, water and sunlight would have significant benefit to society. However, developing photocatalysts capable of sunlight-to-fuel conversion is a challenging problem that requires a fundamental understanding of the chemical reactions taking place on the nanocrystal surface. With support from the Macromolecular, Supramolecular and Nanochemistry Program of the NSF Division of Chemistry, Professor Sadtler at Washington University in St. Louis is developing microscopy methods to watch individual, light-driven reactions as they occur on single nanocrystal photocatalysts. Together, Professor Sadtler and his students are gaining new insights into why some atomic sites on the surface of nanocrystals are particularly active for catalysis. Professor Sadtler is also infusing his research into education. He is developing new courses that use atomic structure and chemical bonding as a basis to teach the frontiers of chemistry and materials science, as well as working with high school teachers and students in the St. Louis area.Metal oxide semiconductor nanocrystals with tunable stoichiometry are promising photocatalysts to produce liquid fuels through solar water splitting, partial methane oxidation, and the reduction of carbon dioxide. However, the contribution of specific structural and morphological features among individual catalyst particles to their ensemble activity is not well understood because each particle is different and possesses a variety of potential reaction sites. This project uses super-resolution fluorescence microscopy and redox-active fluorogenic probes to monitor photoinduced charge-transfer events on individual metal oxide nanocrystals with nanoscale spatial resolution. Correlation of the reactivity maps with the atomic resolution of scanning transmission electron microscopy performed on the same particles reveals how the distribution of oxygen vacancies in individual particles affects their reactivity. To further develop structure-activity relationships in metal oxide photocatalysts, the single-molecule, single-particle data are compared to measurements of bulk photocatalytic activity for methane oxidation and carbon dioxide reduction.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.