Ligand Control Over Electronic Structure in Metallic Nanoparticles and Model Clusters

点击翻译按钮获取中文摘要

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.