The Influence of Defects and Adsorption on the Local Electronic Potential of Supported Metal Nanoclusters

在这个由化学系大分子，超分子和纳米化学项目资助的项目中，加州大学滨江分校的Jory Yarmoff教授研究了纳米颗粒的性质如何受到其支撑表面的影响。 纳米粒子是包含数千个原子的微小粒子。虽然它们比只包含几个原子的化学分子大得多，但它们仍然比包含数万亿个原子的固体材料小得多。纳米尺度材料是独特的，因为它们的尺寸介于分子和固体之间，但有时具有不容易通过平均两个极端尺寸来预测的特性。 Yarmoff教授使用专门的表征方法来研究金属纳米颗粒的电子特性如何受到固体支撑材料中缺陷的影响。 测量是作为纳米颗粒尺寸、载体材料中有意产生的缺陷的数量和暴露于“粘附”（或吸附）到簇的气体的函数进行的。该研究在表面化学领域具有重要的广泛影响。学习如何控制纳米粒子的电子特性将有助于它们在许多应用中的使用，如电子，超级电容器，锂离子电池，太阳能发电和催化。该研究项目影响基础科学，技术和环境方面的知识，同时直接促进大学多样化学生的教育。研究生和本科生在现代研究的前沿领域获得实践实验室经验，而当地高中教师则受益于包括实验室经验的暑期课程。在这个项目中，Yarmoff教授研究了支撑金属纳米团簇的局部静电势（LEP）如何受到以下因素的影响：（1）衬底中故意引入缺陷，（2）各种吸附原子吸附到纳米团簇上，以及（3）衬底中的缺陷改变任何后续吸附的方式。尽管对金属纳米团簇的研究越来越多，但仍然有许多未回答的问题，并且对于负责其催化增强和其他性质的潜在机制没有达成共识。然而，有大量的证据表明，金属纳米团簇的电荷状态是其电子和化学行为的关键因素。通过直接沉积和缓冲层辅助生长（BLAG）在氧化物和氟化物衬底上制备负载型金属纳米团簇。 Yarmoff教授使用一种新型的低能离子散射（LEIS）形式来监测纳米团簇的表面LEP和电荷状态，该形式依赖于散射的1-5 keV碱离子的中和。有意产生的缺陷和吸附的小分子的合并用于调整每个簇上的电荷量。这些研究提供了对固态材料的物理和化学性质的理解，同时开发了控制它们的方法，这将有助于它们在纳米电子学，超级电容器，锂离子电池，太阳能发电和催化等众多应用中的使用。该研究计划也有更广泛的教育和推广的影响，因为它直接有助于加州大学河滨分校的研究生和本科生的多元化机构的教育，通过动手实验室经验在一个领域的前沿现代研究。当地的高中教师也受益于包括实验室经验在内的暑期课程。

In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Jory Yarmoff of the University of California at Riverside studies how the properties of nanoparticles are affected by the surfaces on which they are supported. Nanoparticles are tiny particles that contain thousands of atoms. While they are much larger than chemical molecules, which contain only a few atoms, they are still much smaller than solid materials that are large enough to see with the naked eye, containing trillions of atoms. Nanoscale materials are unique because they have sizes intermediate between molecules and solids, but sometimes have properties not easily predicted by averaging the two size extremes. Professor Yarmoff uses specialized characterization methods to investigate how the electronic properties of metal nanoparticles are affected by defects in a solid support material. Measurements are made as a function of nanoparticle size, the number of intentionally produced defects in the support material and exposure to gases that "stick" (or adsorb) to the clusters. The research has significant broader impact in the field of surface chemistry. Learning how to control the electronic properties of nanoparticle will facilitate their use in numerous applications such as electronics, supercapacitors, lithium ion batteries, solar power generation and catalysis. This research project impacts knowledge in basic science, technology and the environment while directly contributing to the education of the university's diverse student body. Graduate and undergraduate students obtain hands-on laboratory experience in a field that is at the forefront of modern research, while local high school teachers benefit from a summer program that includes laboratory experience. In this project professor Yarmoff studies how the local electrostatic potential (LEP) of supported metal nanoclusters is affected by (1) the intentional introduction of defects in the substrate, (2) adsorption of various adatoms onto the nanoclusters, and (3) the manner in which defects in the substrate act to modify any subsequent adsorption. Although there has been a proliferation of research on metal nanoclusters, there are still many unanswered questions and no consensus as to the underlying mechanisms responsible for their catalytic enhancement and other properties. There is a strong body of evidence, however, that the charge state of metal nanoclusters is a critical factor in their electronic and chemical behaviors. Supported metal nanoclusters are produced on oxide and fluoride substrates by direct deposition and buffer layer assisted growth (BLAG). Professor Yarmoff uses a novel form of low energy ion scattering (LEIS), which relies on the neutralization of scattered 1-5 keV alkali ions, to monitor the surface LEP and charge state of the nanoclusters. Incorporation of intentionally produced defects and adsorption of small molecules are used to tune the amount of charge localized on each cluster. The research has significant broader impact on the field; these studies provide an understanding of the physical and chemical properties of solid-state materials while developing methods to control them, which will facilitate their use in numerous applications such as nanoelectronics, supercapacitors, lithium ion batteries, solar power generation and catalysis. The research program also has broader impacts in education and outreach since it directly contributes to the education of the University of California-Riverside's diverse body of graduate and undergraduate students through hands-on laboratory experience in a field at the forefront of modern research. Local high school teachers also benefit from a summer program that includes laboratory experience.