Events

Electronic Structure and Excited State Dynamics in Biological and Nanoscale Systems

February 25, 2009 at 3pm/36-428

Gregory D. Scholes
Department of Chemistry, University of Toronto

abstract:
After photoexcitation, energy absorbed by a molecule can be transferred efficiently over a distance of up to several tens of Ångstrom to another molecule by the process of resonance energy transfer, RET (also commonly known as electronic energy transfer, EET). Examples of where RET is observed include natural and artificial antennae for the capture and energy conversion of light in photosynthesis, amplification of fluorescence-based sensors, optimization of organic light-emitting diodes, and the measurement of structure in biological systems (FRET). Recent experimental work in our laboratory suggests that RET in conjugated polymers may involve surprising electronic coherence. This, in turn, contributes to enhancing the semiconductor-like optical properties of these systems. I will describe an ultrafast polarization experiment specifically designed to observe quantum coherent dynamics in this regime. Our results suggest that quantum transport effects occur at room temperature when chemical bonds connecting donor and acceptor help to correlate dephasing perturbations. A fascinating topic in quantum chemistry is the elucidation and quantification of models for electron correlation, which is crucial for the correct description of electronic excited states. In the second part of this talk I will discuss experiments that we have used to probe electron correlation in molecules and nanoscale systems, such as nanocrystals and carbon nanotubes.

bio:
Dr. Scholes obtained both his B.Sc. (Hons) and Ph.D. (1994) from the University of Melbourne. He undertook postdoctoral studies at Imperial College in London from 1995–1997 as a Ramsay Memorial Research Fellow. During the period 1997–2000 he pursued further postdoctoral studies at the University of California, Berkeley (with Prof Graham Fleming, presently Deputy Director of Lawrence Berkeley National Lab). He subsequently took a faculty position at the University of Toronto, in the Department of Chemistry (2000) and was promoted to Associate Professor in 2005. Dr. Scholes took research and study leave during 2006–2007, and spent productive and enoyable time at the National Renewable Energy Laboratory (Colorado, USA) and Università di Pisa (Toscana, Italia). Recent awards honoring his research achievements include the 2007 Royal Society of Canada Rutherford Medal in Chemistry, a 2007 NSERC Steacie Fellowship, the 2006 Canadian Society of Chemistry Keith Laidler Award, and an Alfred P. Sloan Fellowship (2005–2006).