December 8, 2014
Speaker: Dr. Denis V. Potapenko, Dept. of Applied Physics and Applied Mathematics, Columbia University
Understanding of the behavior of photo-generated electrical charges at the interface of the semiconductor is crucial for renewable solar-energy technologies such as photocatalysis and photovoltaics. In our laboratory we explore the charge-induced phenomena on the surface of a semiconductor on a single-molecule scale using Scanning Tunneling Microscopy (STM) as our primary research tool and titanium dioxide (TiO2) as a model photo-active semiconductor. TiO2 is a versatile photocatalytic material and it has been the subject of extensive research over the last two decades. We have studied both single-crystal rutile(110) surface and arrays of TiO2 nanocrystals prepared in situ on an Au(111) surface. Photo-induced desorption tri-methyl acetic acid (TMAA) molecules adsorbed on TiO2 surfaces has been selected as a model photocatalytic reaction. By using monochromatic light from a UV-vis lamp to drive the surface photoreactions, we demonstrate strong dependence of the reaction rates on both the wavelength of the incident light and the state of the surface. The TiO2 nanocrystals are shown to be also photoactive for desorption of TMAA from an ordered template. Finally experiments to investigate the electron- and hole-induced chemistry on rutile(110) surface by injecting charges from the STM tip directly into an adsorbed molecule or into the substrate are reported.
Denis V. Potapenko earned his M.S. degree in Applied Physics from Moscow Institute of Physics and Technology (MIPT) and his Ph.D. in Chemistry from Rutgers, the State University of New Jersey. He has worked in different areas of the chemistry of surfaces, with specialization in the field of nano-catalysis. After finishing postdoctoral studies at Brookhaven National Laboratory (BNL) in 2006, Denis joined Prof. Richard Osgood's research group at Columbia University as a Research Scientist.
Hosted by Richard Osgood.