Seminar:

Profile: Research interests include electronic and vibrational nonlinear spectroscopy at interfaces; photocatalysis, photovoltaics and plasmonics in nanomaterials, and nanoelectronics; bonding and reactivity at environmental interfaces; laser spectroscopy techniques and chemical instrumentation. For more information, visit Dr. Velarde's profile here and his lab's website.

Abstract: Understanding the delicate interplay between nuclear motion and electronic structure at interfaces is a challenging task of high relevance to many scientific areas such as photocatalysis, photovoltaics, and nanophotonics. We demonstrate that Doubly-Resonance Sum Frequency Generation (DR-SFG) spectroscopy can be used as a surface and species-selective probe in order to characterize how specific vibrational modes of interfacial species are coupled to excited surface electronic states and influence functional properties of materials. We show how second-order nonlinear probes of vibronic coupling can shed light on surface aggregates in photosensitized catalysts, structural conformers of substituted azobenzene molecules on surfaces, and in phonon-assisted transitions in nanostructured carbon films at buried interfaces. These studies allow us to gain insights into how specific nuclear motions may selectively drive electronic processes at surfaces. The talk will demonstrate how sum frequency generation vibrational spectroscopy can be used to examine the binding, orientation, and ordering in solution-processed nanomaterials and provide an opportunity for the development of controlled chemistries for the design of layered materials and surfaces with tailored properties.