About the Seminar:
The Crowther Group uses micro-Raman spectroscopy to investigate the vibrational and electronic properties of a variety of nanostructures. Semiconducting nanocrystals occupy a size regime between the molecular and bulk limits. Nanocrystal vibrational structure can be described using either a molecular “bottom-up” quantum chemical approach or via a “top-down” phonon confinement model that truncates bulk phonons at the nanocrystal boundaries. We use temperature-dependent Raman spectroscopy to identify the size transition from molecular vibrations to confined phonons in a series of atomically precise cadmium selenide quantum dots of tetrahedral shape with edges that range from 1.7 nm to 2.6 nm in length. Surprisingly, as little as one unit cell in the nanocrystal is sufficient to successfully apply a phonon confinement model. In a second project, we use Raman spectroscopy to measure how solvation affects the surface adsorption and electron-transfer dynamics between graphene and iodine. Understanding these solvation effects is a necessary prerequisite for many graphene applications. Solution-phase isotherms demonstrate that solvent polarity drives surface adsorption and that the subsequent electron transfer from graphene to iodine is strongly influenced by solvent-I2 complexes.
About the Speaker:
Andrew Crowther earned his B.A in Chemistry from Washington University in St. Louis in 2002 and his Ph.D. in Chemistry under the supervision of Professor F. Fleming Crim at the University of Wisconsin-Madison in 2008. He then completed a Mirzayan Science and Technology Policy Fellowship at the Board on Chemical Sciences and Technology at the National Research Council, followed by postdoctoral research with Prof. Louis Brus at Columbia University. Professor Crowther has been an Assistant Professor of Chemistry at Barnard College in New York City since 2012, where his research group uses Raman spectroscopy to investigate the fundamental vibrational and electronic properties of nanomaterials. His research has been supported by the American Chemical Society Petroleum Research Fund and the National Science Foundation.