title: Self-Assembled Light-Harvesting System from Chromophores in Lipid Vesicles.
abstract: Lipid vesicles are used as the organizational structure of self-assembled light-harvesting systems. Following analysis of 17 chromophores, six were selected for inclusion in vesicle-based antennas. The complementary absorption features of the chromophores span the near-ultraviolet, visible, and near-infrared region. Although the overall concentration of the pigments is low (~1 μM for quantitative spectroscopic studies) in a cuvette, the lipid-vesicle system affords high concentration (≥10 mM) in the bilayer for efficient energy flow from donor to acceptor. Energy transfer was characterized in 13 representative binary mixtures using static techniques (fluorescence-excitation versus absorptance spectra, quenching of donor fluorescence, modeling emission spectra of a mixture versus components) and time-resolved spectroscopy (fluorescence, ultrafast absorption). Binary donor-acceptor systems that employ a boron-dipyrrin donor (S0 ↔ S1 absorption/emission in the blue-green) and a chlorin or bacteriochlorin acceptor (S0 ↔ S1 absorption/emission in the red or near-infrared) have an average excitation-energy-transfer efficiency (ΦEET) of ~50%. Binary systems with a chlorin donor and a chlorin or bacteriochlorin acceptor have ΦEET ∼ 85%. The differences in ΦEET generally track the donor-fluorescence/acceptor-absorption spectral overlap within a dipole-dipole coupling (Förster) mechanism. Substantial deviation from single-exponential decay of the excited donor (due to the dispersion of donor-acceptor distances) is expected and observed. The time profiles and resulting ΦEET are modeled on the basis of (Förster) energy transfer between chromophores relatively densely packed in a two-dimensional compartment. Initial studies of two ternary and one quaternary combination of chromophores show the enhanced spectral coverage and energy-transfer efficacy expected on the basis of the binary systems. Collectively, this approach may provide one of the simplest designs for self-assembled light-harvesting systems that afford broad solar collection and efficient energy transfer.
authors.affiliation: †Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States.
authors.forename: Tuba
authors.initials: T
authors.lastname: Sahin
authors.affiliation: ‡Department of Chemistry, Washington University, St. Louis, Missouri 63130-4889, United States.
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Harris
authors.affiliation: †Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States.
authors.forename: Pothiappan
authors.initials: P
authors.lastname: Vairaprakash
authors.affiliation: §Photosynthetic Antenna Research Center, Washington University, St. Louis, Missouri 63130-4889, United States.
authors.forename: Dariusz M
authors.initials: DM
authors.lastname: Niedzwiedzki
authors.affiliation: ∥Center for Biomedical Engineering and Department of Chemical and Biological Engineering, University of New Mexico, Albuquerque, New Mexico 87131-0001, United States.
authors.forename: Vijaya
authors.initials: V
authors.lastname: Subramanian
authors.affiliation: ∥Center for Biomedical Engineering and Department of Chemical and Biological Engineering, University of New Mexico, Albuquerque, New Mexico 87131-0001, United States.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Shreve
authors.affiliation: ⊥Department of Chemistry, University of California, Riverside, California 92521-0403, United States.
authors.forename: David F
authors.initials: DF
authors.lastname: Bocian
authors.affiliation: ‡Department of Chemistry, Washington University, St. Louis, Missouri 63130-4889, United States.
authors.forename: Dewey
authors.initials: D
authors.lastname: Holten
authors.affiliation: †Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States.
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Lindsey
mesh_terms: D001895:Boron / Q000737:chemistry; D003198:Computer Simulation; D031541:Fluorescence Resonance Energy Transfer; D007700:Kinetics; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry; D008956:Models, Chemical; D010713:Phosphatidylcholines / Q000737:chemistry; D055668:Photochemical Processes; D011166:Porphyrins / Q000737:chemistry; D013057:Spectrum Analysis; D053835:Unilamellar Liposomes / Q000737:chemistry*
chemical_list: D045342:Light-Harvesting Protein Complexes; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D011166:Porphyrins; D053835:Unilamellar Liposomes; C452433:bacteriochlorin; C006969:chlorin; D001895:Boron