Ligand Control Over Electronic Structure in Metallic Nanoparticles and Model Clusters

化学系的大分子、超分子和纳米化学计划支持宾夕法尼亚州立大学的本杰明·李尔教授开发对调整纳米级金属的各种性质非常重要的新测量技术。在人类历史上，金属已经被证明是如此有用，以至于标志着不同的时代，例如青铜、钢铁和钢铁时代。现代金属的一些先进应用利用了金属纳米颗粒，这种微小的金属颗粒比人类头发的厚度小1000倍。在这些尺度上，金属的性质发生变化，产生了用于感知和治疗癌症、帮助生产高价值化学品以及从环境中消除污染物的行为。进一步开发这些应用的一个关键挑战是测量金属纳米颗粒的性质。李尔教授的团队开发了测量这些性质的新方法，然后利用这些测量来理解金属周围的化学环境如何被用来调节它们的活性。除了预期在化学、物理和材料科学等多学科领域的技术影响外，该团队还从宾夕法尼亚州各地引入高中生参与这项研究的各个方面。该项目有助于对这些学生进行现代科学方面的培训，因为它使他们能够在科学、技术、工程和数学领域做出更明智的决定。在化学部大分子、超分子和纳米化学项目的支持下，研究小组开发了基于金属感应磁性的新测量技术。通过对纳米颗粒施加磁场，该团队可以分离出与其有用的电子行为密切相关的金属的电子性质。具体地说，他们使用泡利顺磁性来研究金属费米能量附近的态密度和这些态的性质。该属性控制诸如导电性和催化活性等行为。该团队同时使用电子自旋共振和核磁共振技术来实现这些测量。该团队首先合成了金属纳米颗粒和非金属原子精密簇合物，两者都由表面的有机配体稳定。然后，研究小组对这些纳米颗粒的大小、形状和表面化学进行了表征。随后，该团队测量了电子和磁性，并开发了模型来解释表面化学对测量性质的影响。最终目标是为科学界提供新的工具和新的见解，以指导基于纳米金属的应用程序的开发。该奖项反映了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。

The Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division supports Professor Benjamin Lear at the Pennsylvania State University to develop new measurement techniques important for tuning various properties of nanoscale metals. In the history of mankind, metals have proven so useful they mark epochs, such as the bronze, iron, and steel ages. Some of the advanced applications of metals in our modern age utilize metal nanoparticles, small metal particles that are 1000 times smaller than the thickness of a human hair. At these scales, the properties of the metals change, giving rise to behaviors that are used to sense and treat cancer, to aid in the production of high-value chemicals, and to eliminate pollutants from the environment. A key challenge in further developing these applications is the measurement of the metal nanoparticles' properties. Professor Lear’s team develops new approaches to measuring these properties and then uses these measurements to understand how the chemical environment around metals can be used to tune their activity. In addition to the technical impacts expected in the multidisciplinary areas of chemistry, physics, and materials science, the team brings in high school students from areas across Pennsylvania to participate in various aspects of this research. This project contributes to training these students in modern science as it allows them to make more informed decisions about pursuing careers in science, technology, engineering, and math. With this support from the Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division, the research team develops new measurement techniques based upon the induced magnetic properties of metals. By applying magnetic fields to nanoparticles, the team can isolate the electronic properties of the metals that are tightly linked to their useful electronic behaviors. Specifically, they use Pauli paramagnetism to study the density of states and the nature of these states near the Fermi energy of the metal. This property controls behaviors such as electrical conductivity and catalytic activity. The team uses both electron spin resonance and nuclear magnetic resonance techniques to achieve these measurements. The team first synthesizes metallic nanoparticles and non-metallic atomically precise clusters, both stabilized by organic ligands at the surface. The team then characterizes the size, shape, and surface chemistry of these nanoparticles. Subsequently, the team measures the electronic and magnetic properties and develops models to account for the influence of the surface chemistry on the measured properties. The end goal is to produce new tools for the scientific community and new insight that can guide the development of applications based upon nanoscale metals.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.