Surface Science on the Nanoscale and Optical Analogs of 2D-NMR
Patanjali Kambhampati
Department of Chemistry
McGill University
Abstract: To be discussed are two new directions in our research group that have emerged from a decade of work on ultrafast exciton dynamics in semiconductor nanocrystals. In both cases we connect classical ideas in physical chemistry to new opportunities in materials science.
The semiconductor nanocrystal is a cluster on the length scale of 1 – 10 nm, at which point quantum confinement effects arise. In this regime one has the standard quantum dot, characterized by excitons, now well understood. By virtue of their small size, these nanocrystals also have pronounced surface effects. Despite its importance the nanoscience community’s understanding of the surface of these materials is in its infancy. Using simple temperature dependent fluorescence spectroscopy, we have shown that the surface can be understood in terms of classical concepts from molecular electron transfer theory. We report here on recent chemical and spectroscopic work that reveals how the surface of semiconductor nanocrystals may be understood, controlled, and exploited.
For a decade our group has employed State-Resolved Pump/Probe spectroscopy to probe ultrafast exciton dynamics in semiconductor quantum dots. These time resolved spectroscopies with one frequency dimension have indeed been useful, but newer multidimensional time-resolved methods have been available for over a decade. These sophisticated Coherent Multidimensional Spectroscopy (CMDS) experiments, can be considered as optical analogs to 2DNMR, albeit with complex beam geometries. Our recent work using laser pulse shaping approaches shows how one can create femtosecond laser pulse trains that are suitably modulated in an automated and programmable manner so as to enable CMDS in a fully collinear approach using all-optical readout.
Bio: Dr. Kambhampatiis an Associate Professor in the Department of Chemistry at McGill University and is an internationally recognized expert on semiconductor quantum dots and ultrafast laser spectroscopy. The quality of the research is evidenced by the number of departmental colloquia delivered at leading institutions. Representative departments in which he has lectured include, MIT, Princeton, Columbia, Pennsylvania, Toronto, U of Chicago, Northwestern, Illinois, Wisconsin, Michigan, Texas, Washington, UCLA, USC. The quality of this work is also evidenced by the work generating five invited review articles in four years.
For more information, see the group web page of Prof. Kambhampati
Cette conférence est présentée par le RQMP Versant Nord du Département de physique de l'Université de Montréal et de Génie physique de la Polytechnique.
