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.
