Nonlinear Absorption in Acceptor Containing Molecular Species: Searching ( )

Nonlinear Absorption in Acceptor Containing Molecular Species: Searching for Large and Long-lived Nonlinear Absorption 

Abstract：In this talk we will discuss our results on the nonlinear absorption properties of three studies where a centralized acceptor group, typically a squaraine unit, has increased the strength of the nonlinear absorption when compared to similar or identical molecules without it.  In the first study, the molecules with the acceptors exhibited a maximum two photon absorption (2PA) cross section approximately 8x that of the same molecule without an acceptor unit.  In the following study, a squaraine bridge was used to link two porphyrin molecules together in an attempt to increase 2PA, which is not typically large in porphyrins, and to increase the triplet absorption and intersystem crossing rate, which is not typically found in squaraines. This resulted in a mixed outcome.  The 2PA significantly increased compared to their constituents, but the long-lived triplet absorption that was anticipated was very small, not what we were expecting considering there were two porphyrins attached to the squaraine.  Finally, a squarainecontainingsulfur, a thiosquaraine, was studied, and its nonlinear absorption characterization showed a triplet yield of nearly 100% with a lifetime of almost 250 ns while its counterpart, a typical oxygen containing squaraine, showed no evidence of triplets, in fact showed a fluorescence quantum yield of nearly 100 %. 

Speaker：Dr. Scott Webster, University of Central Florida, Senior Research Scientist, Ph.D. from Wake Forest University

Scott Webster, Ph.D. received his doctorate in physics from Wake Forest University in 2003 investigating the “Optical Characterization of Nanostructured Materials”.  From 2004 to present, he has worked at CREOL, the College of Optics and Photonics at the University of Central Florida as a Senior Research Scientist.  He has published 62 refereed journal publications, 81 refereed conference proceedings and extended abstracts, presented 37 talks, lectures, and colloquia, has contributed to more than 90 other presentations, and has more than 1600 citations.  As of 2015, he has an h-index of 25. 

For roughly the last 10 years he has multitasked multiple programs in the linear and nonlinear characterization of organics, semiconductors, gasses, and plasmonic nanostructures in the femtosecond to nanosecond time regime and from the ultraviolet to the infrared spectral regime.  His specialty has been the linear and nonlinear characterization of Polymethine and Polymethine-like molecules for nonlinear absorption applications such as optical limiting.

时  间： 2015年6月17日  下午2点-4点

地  点：东区三教614会议室

主办单位：光电工程学院