Charge distribution within supported metal nanoclusters and how it is influenced by the substrate, adsorption and surface defects

Jory A.加州大学滨江分校的Yarmoff得到化学系大分子、超分子和纳米化学项目的支持，研究负载金属纳米团簇内的电荷分布。 Yarmoff教授和他的学生使用专门的表征方法来研究金属纳米颗粒的性质如何受到它们所处的支撑材料的性质的影响，以及支撑中的缺陷如何改变它们的性质。特别是，他们测量团簇内单个原子的电荷，并观察团簇大小和支持缺陷的数量如何影响哪些分子会或不会粘在支持物上。 纳米粒子是一类独特的材料，因为它们的大小介于分子（几个原子）和固体（数万亿个原子）之间。 纳米材料表现出独特的化学和电子性质，这取决于它们的大小，导致许多潜在的应用，包括先进的电子，电池技术，太阳能发电，环境修复和化学催化。 了解并学习如何控制纳米材料的性质，会影响基础科学和实际应用的知识。 在加州大学河滨分校，一个西班牙裔的服务机构，研究生和本科生的多元化群体，正在通过在现代科学的前沿领域进行实验室实验获得宝贵的经验。此外，还通过多方面的内部和外联举措传播研究成果。 这包括参加暑期物理教师学院，为期一周的研讨会，其中包括动手实验室经验，以培训当地高中教师，并激发学生对STEM职业的兴趣。 负载的金属纳米团簇的边缘原子可以是活性位点，其通过将前体分子吸附到直接键合到衬底的团簇原子来驱动化学反应。也有强有力的证据表明，金属纳米团簇的电子环境是决定其电子和化学行为的关键。负载的金属纳米团簇直接沉积或通过缓冲层辅助生长（BLAG）产生到氧化物、硫化物、氟化物和冷冻惰性气体基底上。利用一种新的低能离子散射（LEIS）方法，通过测量散射低能碱金属离子的中和作用，研究了金属纳米团簇内的电荷分布。这种方法以前表明，金纳米团簇内的电荷是不均匀的，边缘原子带正电，而中心原子基本上是中性的。该项目建立在这一知识的基础上，通过探索电荷分布如何取决于集群和基板材料，在集群/支持界面的缺陷的数量，随后的电负性和电正性吸附原子和小分子的吸附，以及基板中的缺陷如何修改吸附。研究结果有助于对金属纳米团簇的基本理解，从而使其性能的定制能够改善功能和实际效用。该研究可能会对该领域产生重大而广泛的影响，因为它提供了对纳米级材料物理和化学性质的了解，同时开发了控制它们的方法，这将促进它们在许多先进制造应用中的使用。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Professor Jory A. Yarmoff of the University of California - Riverside is supported by the Macromolecular, Supramolecular, and Nanochemistry Program in the Division of Chemistry to study the charge distribution within supported metal nanoclusters. Professor Yarmoff and his students use specialized characterization methods to investigate how the properties of metal nanoparticles are affected by the nature of the support material on which they reside and how defects in the support alter their properties. In particular, they measure the charge on individual atoms within the clusters and observe how the cluster size and number of support defects affect what molecules will or will not stick to the supports. Nanoparticles are a distinctive class of materials because they have sizes intermediate between molecules (few atoms) and solids (trillions of atoms). Nanoscale materials exhibit unique chemical and electronic properties that depend on their size, leading to many potential applications that include advanced electronics, battery technologies, solar power generation, environmental remediation, and chemical catalysis. Understanding, and then learning how to control the properties of nanoscale materials broadly, impacts knowledge in basic science and practical applications. A diverse group of graduate and undergraduate students at the University of California-Riverside, an Hispanic serving institution, are gaining valuable experience by conducting laboratory experiments in a field at the forefront of modern science. In addition, the research results are disseminated via multifaceted in-house and outreach initiatives. This includes participation in a Summer Physics Teachers Academy, a week-long workshop which includes hands-on laboratory experiences to train local high school teachers and stimulate the interest of their students in STEM careers. The edge atoms of supported metal nanoclusters may be the active sites that drive chemical reactions via adsorption of precursor molecules to the cluster atoms that are directly bonded to the substrate. There is also strong evidence that the electronic environment of metal nanoclusters is critical in determining their electronic and chemical behaviors. Supported metal nanoclusters are directly deposited, or produced by buffer layer assisted growth (BLAG), onto oxide, sulfide, fluoride and frozen noble gas substrates. A novel form of low energy ion scattering (LEIS) is used to investigate the charge distribution within metal nanoclusters by measuring the neutralization of scattered low energy alkali ions. This method previously showed that the charge within a gold nanocluster is inhomogeneous, with the edge atoms being positively charged while the center atoms are essentially neutral. This project builds on this knowledge by exploring how the charge distribution depends on the cluster and substrate materials, the number of defects at the cluster/support interface, the subsequent adsorption of electronegative and electropositive adatoms and small molecules, and how defects in the substrate modify adsorption. The research results wicontribute to a fundamental understanding of metal nanoclusters, thereby enabling the tailoring of their properties to improve functionality and practical utility. The research may have a significant and broad impact on the field by providing an understanding of the physical and chemical properties of nanoscale materials while developing methods to control them, which will facilitate their use in numerous advanced manufacturing applications.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.