Transcript Chimica Fisica dei Materiali Avanzati Parte I

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
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Nomenclature of dendrimers
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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
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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
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Functional dendrimers
Functional units at
the periphery
Functional units in the
branching points
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Functional units in
the core
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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
 ….
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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
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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.
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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
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Light harvesting sytems
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… an example
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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
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Chemical sensors
Conventional
fluorescent sensor
Fluorescent sensor
with high signal
amplification
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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
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Light controlled drug delivery systems
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Medical applications: photodynamic therapy
O2
Light
absorption
1O
2
Singlet
oxygen
production
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