Conventional Properties

Quantum Size Effects A chemist likes to keep track of material in grams or in moles, where a 1 mole = 6 x 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

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.

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

giga mega kilo milli micro nano pico 1,000,000,000 1,000,000 1, , ,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

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

Conventional Properties

NanoPeriodic Table – Under construction

Quantum Size Effects A chemist likes to keep track of material in grams or in “moles”, where a mole equals 6 x 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

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

Energy Quantization

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