Applied Physics Seminar

NOTE! Every student or postdoc (any option!) will receive a $5 SmartCash "coffee credit" for each Applied Physics lecture attended. The credits will be tallied and issued after the last speaker of the term.

Abstract:

I will present data on vibrational spectroscopy alongside ab initio simulations to ‘visualize' chemical reactions in plasmonic nanogaps in order to understand physical and chemical cues governing reactions between functional groups on molecules. An experimental platform, using electrohydrodynamic (EHD) flow, which produces flow fields in solution with components parallel to an electrode surface in the presence of a perturbation, is used to facilitate interactions between plasmonic nanoparticles (NP). We monitor chemical reactions using in situ surface-enhanced Raman scattering (SERS).

Carbodiimide coupling chemistry as a function of molecular structure (lipoic acid, 4-mercaptobenzoic acid, and 4-mercaptophenylacetic acid ligands) are studied to represent a range of aromaticity and electron delocalization to probe how the electronic structure of molecules affects reactivity. Theory and experiment indicate that chemical reactions within nanogaps are promoted by the confined geometry, i.e., entropically driven sampling of molecular conformations in nanogaps. Anhydride bond formation between carboxylic acid groups appears to be a rare event, thus the long range EHD driving force allows chemical reactions with high activation energy barriers to proceed in observable time frames. Carbodiimide-fueled anhydride formation is a potential fuel for non-equilibrium chemical assembly where reaction rates can be tuned to form supramolecular structures with spatiotemporal control in order to design adaptive behavior. The temporal evolution of an acetylation reaction between nucleophiles and aliphatic anhydrides in plasmonic nanogaps will also be presented and as well as sensing applications to monitor biochemical processes in living systems.

More about the Speaker:

Prof. Ragan is a Professor in the Department of Material Science and Engineering and co-PI of the Center for Complex and Active Materials, a NSF MRSEC at UC Irvine. She has served as Equity Advisor, Inclusive Excellence Professor, and Diversity Director in Engineering Education. She is a recipient of the National Science Foundation Faculty Early CAREER Award and a Fulbright Fellow. Before joining UC Irvine, she received her B.S. summa cum laude in Material Science and Engineering from the University of California, Los Angeles, Ph.D. in Applied Physics from the California Institute of Technology, and was a postdoctoral scholar in the Information & Quantum Systems Laboratory at Hewlett Packard.