UC Irvine

Self-assembly typically utilizes thermodynamic driving forces to organize building blocks ranging from atoms to nanoparticles into static assemblies. Self-assembled structures often exhibit unique properties such as lowering catalytic energy barriers or tuning light-matter interactions. This requires understanding how to design and fabricate surfaces at atomic and molecular length scales where localized forces such as magnetic or electric fields drive complex chemical behavior. The characterization of nanoscale chemical behavior necessary for complete understanding of these processes is a significant challenge. In terms of catalysis, high throughput density functional theory modeling of a range of earth abundant transition metal atoms (V, Fe, Mo, Ta) supported on two types of graphene surface defects (bare, N-doped) demonstrate relatively lower activation energy barriers for systems with higher spin states at frontier orbitals near the Fermi energy; CO oxidation on Ta and V SAC have decreases in activation barrier energies of 27% and 44%, respectively. Effective Raman and infrared (IR) modeling approaches have been developed to interpret the effects of charge transfer and electric fields on chemical bonding and molecular orientation in plasmonic nanogaps. Even non-plasmonic enhancement of electric fields on gold surfaces is shown to alter molecular orientation and selectively enhance resonance modes in vibrational force spectra, which correlates to IR spectroscopy. The insights provided by this work further elucidates nanoscale chemical reactions crucial for next generation catalytic design as well as fundamental understanding of dynamic chemical behavior during self-assembly processes.