1. Does all Gold Glitter?

2. You will work together in groups of 2 or 3 and play “Duckboy in Nanoland” as an introduction to the basic principles of Nanoscience. http://www.sciencemuseum.org.uk/antenna/nano/

3. The properties of matter change with scale. In particular, as the size of a material approaches the nanoscale it often exhibits unexpected properties that lead to new functionality. As the size of an object approaches the nanoscale, the amount of material becomes critical and all properties are impacted by the size and shape of the material.

4. Activity: Observe and Test Properties of Bulk Gold. The bulk metallic properties of gold will be discussed and demonstrated by passing around samples of old gold jewelry, gold leaf and gold Cd’s. You will test and observe the following properties: malleability, luster, color, and conductivity.

5. The metallic properties of bulk gold can be related to the electron sea model of metallic bonding. You will observe that even with the gold layer only 0.1µm thick in the gold leaf, it still maintains the properties of bulk gold.

6. You will observe the removal of the plastic covering of a gold CD to uncover the 50 -100 nm gold layer. Pieces of the gold CD layer will be passed around and you will observe the properties of gold at this thickness. The properties of color, luster and conductivity will remain even though the gold is now only 50-100 nm’s in thickness.

7. Dissolve the protective acrylic coating on the surface of the Au-CD with nitric acid, it will take at least 40 s for the CD and acrylic to separate. Avoid pulling the acrylic layer off as this will result in a scratched surface. Warning: nitric acid is a strong acid, and direct skin and eye exposure must be avoided. Carefully pour the nitric acid into a waste container Cut a small piece from the Au-CD.

8. Rinse the Au-CD piece with distilled water and dry completely. This process should leave the relief structure of the Au-CD exposed. This gold piece can now be used to test color, luster and conductivity.

9. Pieces of the gold CD layer will be passed around and you will observe the properties of gold at this thickness. The properties of color, luster and conductivity will remain even though the gold is now only 50-100 nm’s in thickness.

10. The reflective layer of gold, archival CDs contains pure 24 karat elemental gold. These products look gold because the reflective layer is gold. 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. The amount of gold in a Gold disc reflective layer is approximately 14mg. Gold electrodes are widely used in electrochemistry and electroanalytical chemistry. You can construct gold electrodes using recordable CDs as the gold source. The nanometer thickness of the gold layer of recordable disks (50 − 100 nm) favors the construction of band nanoelectrodes.

11. Size-Dependent Properties How do the properties of gold change at the nanoscale?

12. The properties of matter are size dependent and as the size approaches the nanoscale the physical properties will often be unexpected.

13. In this laboratory activity, you will follow the process of nanoparticle aggregation by observing the color change of a solution of gold nanoparticles.

14. The color of a gold nanoparticle solution depends on the size and shape of the nanoparticles. The volume and shape of a nanoparticle determines how it interacts with light. Accordingly, this determines the color of a nanoparticle solution. For example, while a large sample of gold, such as in jewelry, appears yellow, a solution of nano-sized particles of gold can appear to be a wide variety of colors, depending on the size of the nanoparticles. In this activity, you will explore these size-dependent properties of gold nanoparticles and investigate the effect of adding different substances.

15. Different Sizes of Collodial Gold Particles

16. Optical Properties of Gold

17. 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

18. 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

19. You will: Make gold nanoparticles. Determine the color of the nanoparticles. Determine the size of the nanoparticles.

20. A solution of HAuCl 4 is heated until it comes to a boil (far left). After a 1% sodium citrate solution is added, 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.

24. The presence of a colloidal suspension can be detected by the reflection of a laser beam from the suspended nanoparticles.

25. Put a small amount of the red gold nanoparticle solution in two test tubes. Use one tube as a color reference and add 5-10 drops of NaCl solution to the other tube. Does the color of the solution change as the addition of chloride makes the nanoparticles closer together? 1. 2. 3.4.

26. 1. 2. 3.4. A layer of absorbed citrate anions on the surface of gold nanoparticles keep the nanoparticles separated (left). Addition of smaller chloride ions (right) allows the particles to approach more closely and a color change is observed.

31. The color of nano-gold particles depends on the distance between the particles.

33. 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 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 http://www.nanocemms.uiuc.edu/content/education/online_labs /01/index.php

34. SEM picture of colloidal gold

35. 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) Review the concept that properties of matter change with scale. As the size of a material approaches the nanoscale it often exhibits unexpected properties. As the size of an object approaches the nanoscale, the amount of material becomes critical and all properties are impacted by the size and shape of the material.