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Nano Chemistry?
Cells
Atoms
Molecules
Macromolecules Protein, DNA..
10-9 m
10-10 m
10-6 m
1 m
Nano
Bottom up building-up of structures!
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Self-Assembly

• Carries out many of the difficult steps in
  nanofabrication
• - atomic-level modification of structure,
• using highly developed techniques of
  synthetic chemistry
• Inspiration from a wealth of examples in biology
• - Proteins, DNA, cell-membrane etc.
• Target structure is thermodynamically stable
• - structures are relatively defect-free and
  self-healing

• Understanding is still at a very elementary
  level
• - molecular shape
• - Enthalpy vs. Entropy
• - nature of non-covalent forces

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Self-Assembled Monolayers (SAMs)
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Self-Assembled Monolayers (SAMs)
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Self-Assembled Monolayers (SAMs)
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Mixed Self-Assembled Monolayers (SAMs)
Can exploit mixed SAMs to develop tailor designed
materials with gradient of wettability, charge,
polarity etc.
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Self-Assembled Monolayers (SAMs)
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Amphiphiles
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Amphiphiles
Micelles form at CMC - this can be modelled and
easily controlled
They can form direct or reverse micelles
depending on solvent nature
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Amphiphiles on Water
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A.
Hydrophobic groups
Air
Conjugated ?-electron system
Hydrophilic groups
Water
B.
C.
Air
Air
Water
Water
?-stacking of adjacent polymers
Space filling model
J. Am. Chem.Soc. 120, P. 7643,(1998)
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Langmuir-Blodgett
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Langmuir-Blodgett
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Metal Nanoparticles
-Link between the well-established fields of
solid-state and atomic physics (Clusters,
condensed matter in embryonic form) -how many
atoms before bulk? -large surface/volume ratio
(negligible in bulk) -electronic quantum number
n. Dispersion relation E(n) is composed of a
sequence of electronic levels (like atoms and
molecules) -Growth spiral (Magic numbers)
Mackay icosahedra
1, 13, 55, 147, 309, 561 etc.
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Ligand Stabilized Gold Nanoparticles
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Ligand Stabilized Gold Nanoparticles

• Ligand Exchange

Ligand Mobility
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Potential Applications ofMonolayer Protected
Nanoparticles

• Chemical Platforms
• Catalysis
• Chemical Sensors
• Nano-Reactors
• Biological Sciences
• Bio-Sensing
• Drug Delivery
• Therapeutics
• Microscopy Labels

• Materials Science
• Nanoscale Electronics
• Electrooptics
• Photography
• Electronic Inks
• Molecular Machines
• Optical Filters and Switches
• Decorative Applications
• Thin FIlms

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Superstructures
Collective properties Site energies,
interparticle coupling strength, lattice
dimensions Control of superstructure, 2D
nanoarrays (Nanoalloys)
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DNA Gold Nanoparticles - Molecular Recognition
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6 nm
agglomerated
1.4 nm
The change in the optical properties of the
solutions reflects the differences in the mean
free path of the free electrons in the metal
particles.
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Layer-by-Layer
Spatial control - many publications by Frank
Caruso
and a couple by Katakis.
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Branched DNA
Halliday junction contains four DNA strands bound
together to form double helical arms flanking a
branch point Take synthetic DNA with programmed
sticky ends and they will self assemble into
desired structure
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DNA as a scaffold
Can be used to assemble nanoelectronic
components, or for example to position biological
macromolecules so as to study their structure by
X-ray crystalllography
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Dendrimers
Dendros tree Monodisperse polymers of specified
size and weight Spherical shapes with a
well-defined interior and exterior Discovered in
early 1980s by Donald Tomalia
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Dendrimers
In the divergent methods, dendrimer grows
outwards from a multifunctional core molecule In
the convergent approach, the dendrimer is
constructed stepwise, starting from the end
groups and progressing inwards.
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Dendrimers
Application in biosensors, bioreactors,
biocatalysis, drug delivery, diagnostics, MRI
imaging, gene therapy...
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Homework
Select one method of self-assembly each and
describe it and find an application (one page
maximum).