1. Conventional Properties

2. Quantum Size Effects A chemist likes to keep track of material in grams or in moles, where a 1 mole = 6 x 10 23 atoms But how many atoms do you really need … –for gold to become gold-colored ? –for iron to become magnetic ? –for water to flow like a liquid ? 1 < ? < 6 x 10 23

3. Cobalt at the Nanoscale R EPORTS Colloidal Nanocrystal Shape and Size Control: The Case of Cobalt Victor F. Puntes, * Kannan M. Krishnan, A. Paul Alivisatos We show that a relatively simple approach for controlling the colloidal synthesis of anisotropic cadmium selenide semiconductor nanorods can be extended to the size-controlled preparation of magnetic cobalt nanorods as well as spher- ically shaped nanocrystals. This approach helps define a minimum feature set needed to separately control the sizes and shapes of nanocrystals. The resulting cobalt nanocrystals produce interesting two- and three-dimensional super- structures, including ribbons of nanorods.

4. IBM Research, 1992 Copper at the Nanoscale One Atom “Trapped” Electrons 1 nanometer = 1 nm

5. giga mega kilo milli micro nano pico 1,000,000,000 1,000,000 1,000 1 0.001 0.000,001 0.000,000,001 0.000,000,000,001 meter Factors of One Thousand meter = smaller than atoms distance to moon you and me nanoscience U.S.A. U.C.I. pencil lead blood cell

6. Size and Scale 1 nm = 0.000000001 m 10 um = 0.00001 m 1 km = 1000 m 0.1 m 10 Mm = 10,000,000 m Factors of 10,000

7. Conventional Properties

8. NanoPeriodic Table – Under construction

9. Quantum Size Effects A chemist likes to keep track of material in grams or in “moles”, where a mole equals 6 x 10 23 atoms But how many atoms do you really need … –for gold to become gold-colored ? –for iron to become magnetic ? –for water to flow like a liquid ? 1 < ? < 6 x 10 23

10. What’s the Difference? “Quantized” Energy Levels only certain properties are allowed at each size  E = hf = hc/

11. Energy Quantization

12. What’s the Difference? Only certain energies are allowed:  E = hf = hc/, where  is a wavelength scale