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NANOTECHNOLOGY
(SCT3022)
Topic 2:The Fundamental Science Behind
Nanotechnology
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What will you learn from
this chapter
Various types of nanostructures.
Energy bands formed from a solid.
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Structure:Size dependence of properties
Many properties of solids depend on their size range.
Microscopic details become averaged when
investigating bulk materials. Macro- or large- scale range: size (mm to km)
mechanics, electricity and magenetism & optics
averaged properties .
Nanometer range: properties of material change e.g.
mechanical, ferroelectric & ferromagnetic properties.
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Structure:crystal structures
Most solids are crystalline
Atoms arranged in regular manner
Regularity extended long range order
Amorphous materials
E.g. glass and wax
Non regular arrangement - Short range order
What would the find out about the
following:
Amorphous
Atomic orders in liquid and gases
Crystalline structure
Amorphous structure
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Can be presented using Bravais lattices i.e. a
fundamental concept in the description of crystalline
solids.
There are only 5 Bravais lattices in 2D
Structure:crystal structures
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Structure:5 Bravais lattices in 2D
Square
Primitive
rectangular
Centeredrectangular
Hexagonal
Oblique
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Structure:Unit cell
It is very cumbersome to draw entire lattices in 3D so
some small portion of the lattice, having full symmetry
of the lattice, is usually drawn. This small portion when
repeated can generate the whole lattice and is calledthe unit cell.
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Unit cell for each bravais
lattice
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Structure:14 bravais lattices in 3d
There are 14 different Bravais lattices in 3D that are
classified into 7 different crystal systems (only the unit
cells are shown below)
Lowest symmetrya b c,
Triclinic type
Highest symmetry
a = b = c, = == 90oCubic
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Structure:14 bravais lattices in 3d
end-
centered
(FCC)(BCC)(SC)
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Building fcc lattice
First hexagonal close-packed
structure generated
Second face-centred cubic lattice
results (when viewed at different
angle)
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Spaces between atoms
in a lattice
Octahedral arrangement
Tetrahedral
arrangement
Spaces left for smaller
atoms to reside
Number of octahedral
site = number ofspheres
Number of tetrahedral
site = 2 x number of
spheres
Examples : MgO, MgS,
MnO, MnS
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Structures of some
nanoparticles
Source:http://boomeria.org/chemtext
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video for further understanding
http://www.youtube.com/watch?v=QIj0t8MNKls
http://www.youtube.com/watch?v=CsnNbuqxGTk
http://www.youtube.com/watch?v=NYVSI83KiKU
http://www.youtube.com/watch?v=Mm-jqk1TeRY
http://www.youtube.com/watch?v=TIXWnr3sdY4
http://www.youtube.com/watch?v=CsnNbuqxGTkhttp://www.youtube.com/watch?v=CsnNbuqxGTkhttp://www.youtube.com/watch?v=NYVSI83KiKUhttp://www.youtube.com/watch?v=Mm-jqk1TeRYhttp://www.youtube.com/watch?v=TIXWnr3sdY4http://www.youtube.com/watch?v=TIXWnr3sdY4http://www.youtube.com/watch?v=TIXWnr3sdY4http://www.youtube.com/watch?v=Mm-jqk1TeRYhttp://www.youtube.com/watch?v=Mm-jqk1TeRYhttp://www.youtube.com/watch?v=Mm-jqk1TeRYhttp://www.youtube.com/watch?v=NYVSI83KiKUhttp://www.youtube.com/watch?v=NYVSI83KiKUhttp://www.youtube.com/watch?v=CsnNbuqxGTkhttp://www.youtube.com/watch?v=CsnNbuqxGTkhttp://www.youtube.com/watch?v=CsnNbuqxGTkhttp://www.youtube.com/watch?v=CsnNbuqxGTkhttp://www.youtube.com/watch?v=CsnNbuqxGTk8/10/2019 Lecture 3 Nanotech
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Atom stabilization
Au55
Purely metallic FCC nanoparticles.
very reactive, short lifetimes.
Need to be stabilized by adding atomic groups
between atoms and on surfaces.
Au55(PPh3)12Cl6 diameter of 1.4 nm
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Energy bands
When solid is formed, the energy level of the atoms
broaden and form bands with forbidden gaps between
them.
Energy values of electrons exist within one of the bands.
Lower energy bands: narrower & full of electronsdo
not contribute to the electronic properties of a material.
Outer energy bands (valance bands): electron that bond
the crystal together
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Insulators
Contain fixed electrons (localized)
No moving electrons to carry current
Conduction band is far above the valance band (notthermally accessible)
Heat content of insulating material is not sufficient to
raise electrons from VB to CB.
Energy bands:Insulators, semiconductors & Conductors
CB
VB
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Semiconductors
Less gap between CB and VB
Heat content of the material can thermally excite
electrons and produce current
Small electrical current produced
Can be doped with electron donating /accepting
atoms
Energy bands:Insulators, semiconductors & Conductors
CB
VB
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Conductors
Full with delocalized conduction electrons
Efficient in carrying electric current flow
Energy bands:Insulators, semiconductors & Conductors
CB
VB
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Energy bands:Insulators, semiconductors & Conductors
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http://www.youtube.com/watch?v=um-YimkrWMM
http://www.youtube.com/watch?v=y_GZn4o8gaE
video for further understanding
http://www.youtube.com/watch?v=um-YimkrWMMhttp://www.youtube.com/watch?v=y_GZn4o8gaEhttp://www.youtube.com/watch?v=y_GZn4o8gaEhttp://www.youtube.com/watch?v=y_GZn4o8gaEhttp://www.youtube.com/watch?v=um-YimkrWMMhttp://www.youtube.com/watch?v=um-YimkrWMMhttp://www.youtube.com/watch?v=um-YimkrWMM