Transcript gold_nano - MathinScience.info

Does all Gold
Glitter?
Play “Duckboy in Nanoland” as an introduction
to the basic principles of Nanoscience.
http://www.sciencemuseum.org.uk/antenna/nano/
The properties of matter
change with scale.
As the size of an object
approaches the nanoscale all
properties are impacted by the
size and shape of the material.
Activity: Observe and Test Properties of Bulk Gold.
Even with the gold layer only 0.1µm
thick in the gold leaf, it still maintains
the properties of bulk gold.
Cut a small piece
from the Au-CD.
Dissolve the protective acrylic
coating on the surface of the
Au-CD with nitric acid.
Carefully pour the nitric
acid into a waste container.
Rinse the Au-CD piece with
distilled water and dry
completely. This gold piece
can now be used to test
color, luster and
conductivity.
The properties of color,
luster and conductivity
will remain even
though the gold is now
only 50-100 nm’s in
thickness.
The reflective gold layer is typically between
50 and 100 nanometers thick. That's thinner
than a wavelength of light. If you laid 10,000
of these layers on top of each other, you'd
have less than a millimeter thick layer of gold.
Size-Dependent Properties
How do the properties of gold change
at the nanoscale?
In this laboratory activity, you will follow the
process of nanoparticle aggregation by
observing the color change of a solution of
gold nanoparticles.
Different Sizes of Collodial Gold Particles
Optical Properties of Gold
• Bulk gold appears yellow in color.
• Nano-sized gold can appear blue or red in color.
– The particles are so small that electrons are
not free to move about as in bulk gold.
– Because this movement is restricted, the
particles react differently with light.
“Bulk” gold looks yellow
12 nanometer gold particles look red
Quantum Effects
• Classical mechanical models that
we use to understand matter at
the macroscale break down for…
– The very small (nanoscale).
• Quantum mechanics better
describes phenomena that
classical physics cannot, like…
– The colors of nanogold.
Macrogold
Nanogold
You will:
• Make gold
nanoparticles.
• Determine the color
of the nanoparticles.
• Determine the size
of the nanoparticles.
The formation of gold nanoparticles proceeds first as
a faint blue color, followed by a dark violet color and
finally a brilliant orange red color.
The presence of a colloidal
suspension can be
detected by the reflection
of a laser beam from the
suspended nanoparticles.
The color of the solution changes as the addition of
sodium chloride makes the nanoparticles aggregate.
1.
2.
3.
4.
A layer of absorbed citrate anions on the surface of gold
nanoparticles keep the nanoparticles separated (left). Addition of
ions (right) allows the particles to approach more closely and a
color change is observed.
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2.
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4.
The color of nano-gold particles
depends on the distance
between the particles.
SEM picture of colloidal gold
Review the different properties of gold as they were
observed in:
•Bulk properties like gold jewelry and gold leaf (0.1µm)
•The nanolayer of gold on the gold CD (50-100 nm’s)
•The gold nanoparticles in solution (13-20 nm)
This is the website for the University of Wisconsin gold lab that
may give you some good information, images, and movies:
http://mrsec.wisc.edu/Edetc/nanolab/gold/index.html
This is the website for the University of Illinois gold lab that may
give you some good information, images, and movies:
http://www.nanocemms.uiuc.edu/content/education/online_labs
/01/index.php