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CBE Seminar - Prof. Jaehong Kim, Yale University

Thursday, January 26, 2017
9:30am – 10:30am

Storrs Campus
Institute of Materials Science, Rm 20

Two Approaches to Achieve Visible Light Upconversion for Environmental Application

This talk summarizes our most recent advances in developing materials that achieve a light frequency amplification through a process called upconversion (UC). The first approach is based on inorganic luminescent materials doped with lanthanide activators that can convert visible light into germicidal UVC and have been shown to inactivate microorganisms deposited on dry surface and deter biofilm formation under commercial fluorescent light exposure. Upconversion efficiencies of current phosphor systems are too low for practical antimicrobial/biocidal application, however, and methods of enhancing internal optical efficiency are required for further advancement. Various approaches that our lab has developed to enhance the efficiency of phosphors and to realize environmental remediation applications are presented. The second UC approach is based on a completely different mechanism of sensitized triplet-triplet annihilation (TTA) in an organic matrix. In TTA-UC process, a sensitizer excited by absorbing a photon with lower energy transfers absorbed energy to an acceptor/annihilator through triplet−triplet energy transfer (TTET), and two excited acceptors subsequently undergo TTA, emitting an upconverted singlet fluorescence with higher energy. Unfortunately, the application of TTA-UC in the ambient aqueous phase has been severely limited because it typically employs organic and metalloorganic chromophores that are soluble only in organic solvents. Moreover, to prevent triplet-state quenching, the medium must be devoid of oxygen, which is difficult to achieve in practical aqueous-phase scenarios. Various strategies developed in our lab including micro- encapsulation to avoid oxygen quenching and sub-bandgap sensitization of semiconductor photocatalysts for advanced oxidation, bioimaging, and dye-sensitized solar cell applications are presented.

Jaehong Kim is currently Professor and Department Chair of Chemical and Environmental Engineering in School of Engineering and Applied Science in Yale University. His areas of interest include: 1) environmental implication and application of nanomaterials; 2) development of upconversion technology for environmental and energy application; and 3) membrane process and materials development. Kim received B.S. and M.S. degrees in chemical and biological engineering from Seoul National University in Korea in 1995 and 1997, respectively, and a Ph.D. degree in environmental engineering from the University of Illinois at Urbana-Champaign in 2002. He joined the School of Civil and Environmental Engineering at the Georgia Institute of Technology in 2002 as an assistant professor and became associate professor with tenure in 2009 and full professor in 2013. From 2009 to 2012, he held the Carlton S. Wilder Endowed Professorship and most recently held the Georgia Power Distinguished Professorship. From 2012 to 2013, he served as associate

Contact:

leah.winterberger@uconn.edu

Chemical & Biomolecular Engineering (primary), Center for Environmental Science and Engineering, Chemistry Department, Environmental Engineering Seminar Series, UConn Master Calendar

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