CONTROLLING ENERGY TRANSFER AND SPIN DYNAMICS USING STRAINED METAL NANOSTRUCTURES
Abstract
This proposal details a three-year plan to understand how strained metals, confined to the Ångstrom lengthscale, can be used to control interfacial energy transfer and spin-state dynamics. Research will focus on two types of metals: 1) 2D crystalline films and 2) sub-nanometer 3D metal nanoclusters that exhibit competitive spin conserving and conversion relaxation pathways. We will study environmentally stable 2D films of group III metals that form at high-energy silicon carbide surfaces and are passivated by catalytically active graphene. Templated by the silicon carbide lattice, the metals adopt highly strained and otherwise inaccessible structures. We will prepare new metal phases using a range of silicon carbide polytypes (e.g. cubic, hexagonal, etc.) and temperatures. Using correlative second and high harmonic generation along with scanning transmission electron microscopy we will determine the interplay between lattice and electronic structure for these novel metals. We will use femtosecond nonlinear microscopy to determine carrier transfer rates between metals and graphene. The ability to modulate carrier densities in these layers will provide a route to tailor the catalytic properties of the 2D heterostructure and mitigate thermal degradation. In the case of 3D metal nanoclusters, our overall goal is to understand if processes analogous to chirality induced spin selectivity are operative in these systems. Through facile ligand exchange, metal nanoclusters can be converted from achiral to chiral structures. Using a series of compositionally similar, but structurally distinct nanoclusters, we will determine if these modifications influence the degree of transient spin polarization and the relative branching ratios of intersystem crossing and internal conversion. This anticipated structural control is expected to have tremendous implications for metal ion-mediated reduction of atmospheric molecules such as N2O, which is believed to require metal electron intersystem crossing. Advances in this area will be achieved through use of state-resolved variable-temperature variable-magnetic field spectroscopy methods developed in the PI’s laboratory. The primary goals are to: (1) describe the electronic properties and carrier dynamics of strained, few-atomic layer 2D crystalline metals, (2) describe mechanisms of energy transfer between 2D metals and graphene in catalytically relevant heterostructures, (3) determine if chiral environments lead to spin-selective relaxation pathways in sub-nm metals, and (4) understand if spin selectivity in metal nanoclusters depends on initial state preparation. Our findings will be transformative by providing critical insights for the rational design of new materials used to modulate catalyst carrier densities and control intersystem crossing events that mediate small molecule catalysis.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 20, 2023
- Source ID
- FA95502210402
Entities
People
- Kenneth L. Knappenberger
Organizations
- Air Force Office of Scientific Research
- Pennsylvania State University
- United States Air Force