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.

Dissolve the protective acrylic coating on the surface of the Au-CD with nitric acid.

Carefully pour the nitric acid into a waste container.

Cut a small piece from the Au-CD.

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.

12 nanometer gold particles look red“Bulk” gold looks yellow

Macrogold

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.

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.

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.

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