CAREER: CAS: Combining Main Group and Transition Metals to Tune the Electronic Structure, Photophysics, and Photocatalytic Activity of Spinel Oxide Nanocrystals

在化学系大分子、超分子和纳米化学（MSN）项目的支持下，罗彻斯特大学的Kathryn Knowles博士将开发混合金属氧化物纳米晶体的新合成方法，并研究它们的性质。这项研究的目的是对这类纳米晶体的结构-性质关系产生一个全面的基本理解，这种纳米晶体有可能促进利用阳光快速降解水源中的持久性有机污染物。环境中的这些污染物，如染料、杀虫剂、除草剂和“永久性化学品”（全氟烷基化合物和多氟烷基化合物），可能对人类健康产生负面影响。纳米晶体的磁性能使它们在使用后很容易从溶液中回收。诺尔斯博士和她的团队还试图培养本科生和小学生对科学研究的积极态度，方法是让他们参加一些能体现科学研究的创造性和协作性的活动。这些活动包括一个开放式的、以探究为基础的顶点项目，该项目将被纳入高年级本科物理化学课程，并将在国家化学周期间以虚拟形式传播给大量不同类型的小学生的科学活动。本研究的长期目标是使可见光吸收半导体的合理设计能够有效地分离光生电荷和缓慢的载流子重组动力学，用于光收集技术的光活性成分。本研究将整合纳米晶体合成、电子结构计算和光谱测量，以全面了解通用式AB2O4的胶体尖晶石氧化纳米晶体的组成、电子结构、光物理性质和激发态动力学之间的关系。诺尔斯小组将建立一个杂双金属分子簇前体库，这将为广泛的尖晶石氧化物成分提供途径。将主族和过渡金属阳离子结合到同一个金属氧化物纳米晶体中，可以系统地研究含有空s轨道和部分填充3d轨道的金属阳离子结合对金属氧化物纳米晶体的光学、电子和激发态性质的协同效应。密度泛函理论计算、瞬态吸收和电化学阻抗谱以及光催化实验将(i)预测并确认尖晶石氧化纳米晶体的电子和光物理性质与其组成的依赖关系，（ii）将这些纳米晶体的带边氧化还原电位和激发态动力学与它们光催化多种有机污染物氧化降解的能力联系起来。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With the support of the Macromolecular, Supramolecular and Nanochemistry (MSN) Program in the Division of Chemistry, Dr. Kathryn Knowles of the University of Rochester will develop novel synthetic approaches to mixed-metal oxide nanocrystals and investigate their properties. This research aims to generate a comprehensive fundamental understanding of the structure-property relationship in this class of nanocrystals that has the potential to facilitate rapid degradation, using sunlight, of persistent organic pollutants in water sources. These pollutants, such as dyes, pesticides, herbicides, and "forever chemicals" (per- and polyfluoroalkyl compounds), in the environment can have negative impacts on human health. The magnetic properties of the nanocrystals will allow their easy recovery from solution after use. Dr. Knowles and her team also seek to cultivate positive attitudes about scientific research in undergraduate and elementary school students by engaging them in activities that capture the creative and collaborative aspects of scientific research. These activities include an open-ended, inquiry-based capstone project to be incorporated into an upper-level undergraduate physical chemistry course and scientific activities that will be disseminated to a large, diverse cohort of elementary school students in a virtual format during National Chemistry Week.The long-term goal of this research is to enable the rational design of visible light-absorbing semiconductors with efficient separation of photogenerated charges and slow carrier recombination kinetics for used as photoactive components of light-harvesting technology. This research will integrate nanocrystal synthesis, electronic structure calculations, and spectroscopic measurements to generate a comprehensive fundamental understanding of the relationships between composition, electronic structure, photophysical properties, and excited state dynamics of colloidal spinel oxide nanocrystals of general formula AB2O4. The Knowles group will establish a library of heterobimetallic molecular cluster precursors that will provide access to a broad range of spinel oxide compositions. Incorporating main group and transition metal cations into the same metal oxide nanocrystals will enable systematic examination of the synergistic effects of combining metal cations containing empty s-orbitals and partially filled 3d orbitals on the optical, electronic, and excited state properties of metal oxide nanocrystals. Density functional theory calculations, transient absorption and electrochemical impedance spectroscopies, and photocatalysis experiments will (i) predict and confirm the dependence of electronic and photophysical properties of spinel oxide nanocrystals on their composition and (ii) correlate the band-edge redox potentials and excited-state dynamics of these nanocrystals with their ability to photocatalyze the oxidative degradation of a broad range of organic pollutants.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.