Controlling Vibrationally-mediated Spin Dynamics Using Metal Nanostructure

With support from the Macromolecular, Supramolecular, and Nanochemistry (MSN) program in the Division of Chemistry, Professor Kenneth Knappenberger of Pennsylvania State University is combining advanced laser techniques with magnetic fields to study how the structure of metal nanoclusters and the motion of their atoms affects the spin of their electrons. Electron spin plays an important role in many emerging technologies but is difficult to study because the vibrational motion of the nanocluster atoms results in rapid relaxation of the electron spin. Professor Knappenberger and his students will address this challenge by correlating electron spin lifetimes to interactions with specific vibrational modes. An iterative process of magnetic-field laser spectroscopy and metal nanocluster synthesis will be employed to understand electron spin properties of metals. These fundamental studies could impact the advancement of quantum-based technologies, as well as lead to more efficient catalysts, new materials for reducing greenhouse gases, and the development of magnetic materials and optical switches. The project will educate graduate and undergraduate students in advanced experimental methods, as well as impact high school students by providing research opportunities and career development activities. Colloidal monolayer-protected nanoclusters allow the synthesis of structurally well-defined metals that exhibit a diverse range of tunable physical properties. This project is developing novel ligand-exchange strategies in order to understand state-selective spin-vibrational coupling in metal nanoclusters. Transient electronic spin states will be characterized using variable-temperature magneto-photoluminescence spectroscopy, as well as develop a Fourier transform magneto-photoluminescence technique for measuring spin lifetimes and spin vibrational coupling. Experiments performed on metal nanoclusters ranging in size from just a few atoms up to several hundred will show the evolution of spin properties from the molecular to metallic levels. Structural analysis will be accomplished using mass spectrometry, Raman spectroscopy, UV-Visible absorption and circular dichroism spectroscopies, as well as X-ray diffraction. The structural specificity of the metals is expected to result in accurate structure-property correlations for spin dynamics in nanoscale metals, which is necessary to accelerate progress in catalyst design and quantum information sciences.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.