title: Bio serves nano: biological light-harvesting complex as energy donor for semiconductor quantum dots.
abstract: Light-harvesting complex (LHCII) of the photosynthetic apparatus in plants is attached to type-II core-shell CdTe/CdSe/ZnS nanocrystals (quantum dots, QD) exhibiting an absorption band at 710 nm and carrying a dihydrolipoic acid coating for water solubility. LHCII stays functional upon binding to the QD surface and enhances the light utilization of the QDs significantly, similar to its light-harvesting function in photosynthesis. Electronic excitation energy transfer of about 50% efficiency is shown by donor (LHCII) fluorescence quenching as well as sensitized acceptor (QD) emission and corroborated by time-resolved fluorescence measurements. The energy transfer efficiency is commensurable with the expected efficiency calculated according to Förster theory on the basis of the estimated donor-acceptor separation. Light harvesting is particularly efficient in the red spectral domain where QD absorption is relatively low. Excitation over the entire visible spectrum is further improved by complementing the biological pigments in LHCII with a dye attached to the apoprotein; the dye has been chosen to absorb in the "green gap" of the LHCII absorption spectrum and transfers its excitation energy ultimately to QD. This is the first report of a biological light-harvesting complex serving an inorganic semiconductor nanocrystal. Due to the charge separation between the core and the shell in type-II QDs the presented LHCII-QD hybrid complexes are potentially interesting for sensitized charge-transfer and photovoltaic applications.
authors.affiliation: Institut für Allgemeine Botanik, Johannes-Gutenberg-Universität Mainz, Mainz, Germany.
authors.forename: Mara
authors.initials: M
authors.lastname: Werwie
authors.forename: Xiangxing
authors.initials: X
authors.lastname: Xu
authors.forename: Mathias
authors.initials: M
authors.lastname: Haase
authors.forename: Thomas
authors.initials: T
authors.lastname: Basché
authors.forename: Harald
authors.initials: H
authors.lastname: Paulsen
mesh_terms: D000042:Absorption; D019187:Cadmium Compounds / Q000737:chemistry; D004735:Energy Transfer; D005456:Fluorescent Dyes / Q000737:chemistry; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D018532:Pisum sativum / Q000201:enzymology; D045663:Quantum Dots; D018036:Selenium Compounds / Q000737:chemistry; D012666:Semiconductors; D013440:Sulfides / Q000737:chemistry; D013691:Tellurium / Q000737:chemistry; D017967:Zinc Compounds / Q000737:chemistry
chemical_list: D019187:Cadmium Compounds; D005456:Fluorescent Dyes; D045342:Light-Harvesting Protein Complexes; D018036:Selenium Compounds; D013440:Sulfides; D017967:Zinc Compounds; C058667:cadmium selenide; C031238:zinc sulfide; D013691:Tellurium; C028337:cadmium telluride