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UNIVERSITA’ DEGLI STUDI DI PADOVA Laurea specialistica in Scienza e Ingegneria dei Materiali Curriculum Scienza dei Materiali Chimica Fisica dei Materiali Avanzati Part 9 – Dendrimers Corso CFMA. LS-SIMat 1 UNIVERSITA’ DEGLI STUDI DI PADOVA Nomenclature of dendrimers Corso CFMA. LS-SIMat 2 UNIVERSITA’ DEGLI STUDI DI PADOVA Dendrimer synthesis: divergent approach Pros: highly iterative chemistry – good control on different generations – possibility to go to high generations (i.e. obtain very large dendrimers). Cons: number of reaction steps increases rapidly with generation – poor control on structural defects, particularly on high generations Corso CFMA. LS-SIMat 3 UNIVERSITA’ DEGLI STUDI DI PADOVA Dendrimer synthesis: convergent approach Pros: number of reaction steps does not increase rapidly with generations – good control on structural defects – possibility to obtain anisotropic dendrimers Cons: synthesis of large dendrimers is often hindered Corso CFMA. LS-SIMat 4 UNIVERSITA’ DEGLI STUDI DI PADOVA Functional dendrimers Functional units at the periphery Functional units in the branching points Corso CFMA. LS-SIMat Functional units in the core 5 UNIVERSITA’ DEGLI STUDI DI PADOVA From synthesis to applications antenna systems sensors with signal amplification NLO systems nano-reactors drug delivery systems catalysts contrast agents in medical diagnosis molecular batteries Unimolecular micelles templates for nanoparticle synthesis …. Corso CFMA. LS-SIMat 6 UNIVERSITA’ DEGLI STUDI DI PADOVA Molecular light-harvesting antennae An antenna for light harvesting is an organized multicomponent system in which several chromophoric molecular species absorb the incident light and channel the excitation energy to a common acceptor component. Organization must be achieved in the dimensions of time, energy, and space Corso CFMA. LS-SIMat 7 UNIVERSITA’ DEGLI STUDI DI PADOVA Natural antenna systems Structure of the LH2 light-harvesting antenna system of Rhodopseudomonas acidophila which contains rings of 18 (left) and 9 (right) bacteriochlorophyll molecules. The ring of B850 Bchl a molecules The positions of the B800 Bchl a molecules between the helices of the b-apoproteins forming the outer cylindrical wall of the complex. The a-apoproteins are coloured yellow and the bCorso CFMA. LS-SIMat apoproteins green. 8 UNIVERSITA’ DEGLI STUDI DI PADOVA Natural antenna systems - 2 Schematic representation of the overall light harvesting process by LH2 and LH1 antenna complexes in bacterial photosynthesis. RC is the reaction center Kuhlbrandt, Nature, 1995 Corso CFMA. LS-SIMat 9 UNIVERSITA’ DEGLI STUDI DI PADOVA Light harvesting sytems Corso CFMA. LS-SIMat 10 UNIVERSITA’ DEGLI STUDI DI PADOVA … an example Corso CFMA. LS-SIMat 11 UNIVERSITA’ DEGLI STUDI DI PADOVA Dansyl: a commonly used fluorescent dye highly fluorescent molecule useful to probe interactions with: Protons metal ions dyes Absorption and emission spectra in CH3CN:CH2Cl2 5:1 v/v Corso CFMA. LS-SIMat 12 UNIVERSITA’ DEGLI STUDI DI PADOVA Chemical sensors Conventional fluorescent sensor Fluorescent sensor with high signal amplification Corso CFMA. LS-SIMat 13 UNIVERSITA’ DEGLI STUDI DI PADOVA Sensor of metal ions with signal amplification One Co2+ guest is sufficient to quench each one of the 64 dansyl units, when they are excited J. Am. Chem. Soc. 2000, 122, 10398 Corso CFMA. LS-SIMat 14 UNIVERSITA’ DEGLI STUDI DI PADOVA Light controlled drug delivery systems Corso CFMA. LS-SIMat 15 UNIVERSITA’ DEGLI STUDI DI PADOVA Medical applications: photodynamic therapy O2 Light absorption 1O 2 Singlet oxygen production Corso CFMA. LS-SIMat 16