Felix Castellano 
Department of Chemistry, North Carolina State University

Abstract:One focus of our research program involves the study of sensitized triplet fusion (TF) in solution using highly photostable metal-organic chromophores in conjunction with energetically appropriate organic molecules with large singlet-triplet gaps. Selective excitation of the long-wavelength absorbing sensitizer efficiently generates long-lived triplet states that serve as energy transfer donors. In the presence of appropriate molecular acceptors, diffusion controlled triplet-triplet energy transfer takes place, producing the excited triplet state of the acceptor while regenerating the ground state of the sensitizer. When sufficient numbers of the sensitized triplets are produced, TTA takes place which results in either frequency upconverted light or the formation of desired chemical products. Various combinations of donor and acceptor have been explored and data will be presented on a number of these systems spanning light conversions ranging from the near-visible to the near-IR. This presentation will also describe many examples of upconversion phenomena realized in solid-state polymeric materials along with emerging classes of acceptor/annihilator chromophores and materials. TF processes will be shown to operate at high efficiencies with concomitant linear incident power density response, demonstrated in both theory and experiment using non-coherent photons. Upconversion-based photoaction observed in water splitting photoelectrochemical cells and operational photovoltaics will also be discussed.

Felix (Phil) Castellano earned a B.A. in Chemistry from Clark University in 1991 and a Ph.D. in Chemistry from Johns Hopkins University in 1996. Following an NIH Postdoctoral Fellowship at the University of Maryland, School of Medicine, he accepted a position as Assistant Professor at Bowling Green State University in 1998. He was promoted to Associate Professor in 2004, to Professor in 2006, and was appointed Director of the Center for Photochemical Sciences in 2011. In 2013, he moved his research program to North Carolina State University where he is currently a Professor in the Department of Chemistry. His current research focuses on metal-organic chromophore photophysics and energy transfer, photochemical upconversion phenomena, solar fuels photocatalysis, and excited state electron transfer processes. 

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