报告摘要：   Single-molecule microscopy studies have been performed in the frequency- and time-domains on semiconductor quantum wires (QWs) and quantum belts (QBs) to investigate the how the dimensionality of the nanostructures alters the energetics and dynamics of excitons prepared in them. Photoluminescence (PL) intensity blinking that spans the entire lengths of QWs (as long as 20 microns) has been observed with continuous illumination. This blinking suggests that delocalized excitons can be formed when trap sites are photochemically filled. The dimensionality of the QWs also gives rise to a distribution of states, over which excitons can be prepared with differing kinetic energies. As a result, emission from multiple exciton states can be detected from single CdSe QWs at room temperature when using high excitation power densities. The measured PL lifetimes from the different exciton states indicate a systematic decrease with increasing population. Lastly, multiple laser experiments have been performed to further probe the delocalization of excitons within QWs and QBs. All of the observations indicate the potential use for these colloidal semiconductor QWs and QBs in photovoltaic devices.


报告人简介： Richard A. Loomis received a Bachelors of Science degree from Dickinson College, Carlisle, PA in 1989 and then studied under the direction of Professor Marsha I. Lester at the University of Pennsylvania, obtaining a Ph.D. in physical chemistry in 1995. He then received a prestigious National Research Council Postdoctoral Fellowship to work with Professor Stephen R. Leone with the National Institute of Science and Technology (NIST) at the University of Colorado. From 1998 to 2005, Loomis held an Assistant Professor of chemistry position at Washington University in Saint Louis, Missouri. In 2005, he was promoted to the rank of Associate Professor in Chemistry. He is now the Associate Director of the Center, and serves as the Director of Graduate Studies in the Chemistry Department.