From the Nanoworld to the Real World: Using Nanoscience to Teach Leigh M. Smith Department of...

From the Nanoworld to the Real World: Using

Nanoscience to Teach Leigh M. Smith

Department of Physics

University of Cincinnati

www.physics.uc.edu/~smithl

Financially supported by the National Science Foundation (0806700 and 0701703) The Institute for Nanoscale Science and Technology at the University of Cincinnati, the Nano-Biotechnology Initiative at Ohio University and the Australian Research

Council.

Outline

• What is nanoscience?

• Is it really a scientific revolution?

• Understanding quantum dots..

• Quantum Mechanics and Music

• Quantum tunneling and an STM

• Electrons really are waves after all

• Applications

Controlling electron waves…

Cadmium Selenide (CdSe)

Quantum Dots

•Same material (CdSe), different colors!

5 nm1 nm

Controlling electron densities

Gold nanoparticles?

Naomi Halas, Rice

Shaelev, Purdue

Controlling light waves

Silica – Quartz – SiO2

Opals – (Silica)

Biology does it all the time..

Joe Haus, University of Dayton

Change the index of the pores and the reflected color changes…

Tayeb et al, Optics and Photonics News, Feb. 2003

Photonic Band Gap Materials

Opals – Silica SpheresSynthetic 3D photonic band gap materials

But is it a revolution?

• Thomas Kuhn, “The structure of scientific revolutions”

• “Normal” Science• Model of Nature• Test-test-test-test-test

• Crisis• New measurement tools or techniques

• Paradigm Shift• Re-write the textbooks!

• Not just New Tools but we are now creating New Structures in Nature itself

• The way we are doing science is changing!• Breakdown of the division between disciplines

Whither Quantum Dots?

• The origins of quantum mechanics

Black Body Spectrum

• The spectrum and intensity of electromagnetic waves from a black body depend only on its temperature

Atomic Spectra

Neon

Helium Hydrogen

Atoms emit in very narrow bands of light…and the colors emitted are singular signatures of the atoms involved

Rutheford alpha particle scattering

Using undergraduates as slave labor

• In 1909, an undergraduate, Ernest Marsden, was being trained by Geiger. To quote Rutherford (a lecture he gave much later):

• "I had observed the scattering of alpha-particles, and Dr. Geiger in my laboratory had examined it in detail. He found, in thin pieces of heavy metal, that the scattering was usually small, of the order of one degree. One day Geiger came to me and said, "Don't you think that young Marsden, whom I am training in radioactive methods, ought to begin a small research?" Now I had thought that, too, so I said, " Why not let him see if any alpha-particles can be scattered through a large angle?" I may tell you in confidence that I did not believe that they would be, since we knew the alpha-particle was a very fast, massive particle with a great deal of energy, and you could show that if the scattering was due to the accumulated effect of a number of small scatterings, the chance of an alpha-particle's being scattered backward was very small. Then I remember two or three days later Geiger coming to me in great excitement and saying "We have been able to get some of the alpha-particles coming backward …" It was quite the most incredible event that ever happened to me in my life. It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you."

Result….

http://abyss.uoregon.edu/~js/cosmo/lectures/lec08.html

The Bohr Model

http://abyss.uoregon.edu/~js/cosmo/lectures/lec08.html

Electrons as waves….

• Prince Louis de Broglie was a member of an illustrious family, prominent in politics and the military since the 1600's. Louis began his university studies with history, but his elder brother Maurice studied x-rays in his own laboratory, and Louis became interested in physics. He worked with the very new radio telegraphy during the war (World War I).

• The only PhD Thesis which won a Nobel Prize

The Music of Quantum Mechanics…

http://www.youtube.com/watch?v=iUDNQfePKlQ

http://www.youtube.com/watch?v=fN4fIRjMf-M

http://www.nytimes.com/2006/08/27/arts/television/27heff.html

http://www.youtube.com/watch?v=owAj5LiXG5w

Waves on a string

L

2L/1 2L/2 2L/3 2L/4

f = f1 2f1 3f1 4f1

Idea was quite simple

•Radiation pressure p = E/c

•Planck’s E = hf, v = f

•p = E/c = hf/c = h/

• = h/p

•Can explain atomic spectra!

A prince comes to the rescue!

Prince Louis-Victor Pierre Raymond deBroglie

Planck says E = h f = h c/

But Einstein says that E/c = p

So then E/c = h/ = h/p

Davisson-Germer Expt.

The origin of electron microscopes!

A particle in a box…

“Seeing” quantum confinement

1.9 nm 5.2 nm

The Scanning Tunneling Microscope

• Quantum tunneling and seeing atoms

"Figure: Michael Schmid, TU Wien"

http://phet.colorado.edu/simulations/quantum-tunneling/quantum-tunneling.jnlp

•Now there is no doubt at all that electrons are waves!

Assembling 48 iron atoms on copper

The quantum corral

Atomic art…

Applications of Nanoscience

Making CdSe QDs Bio-compatible

Klimov, Los Alamos Science(2003)

Development of Frog Embryo

Animal/Organ Visualization

Cancer Resection - Biopsy

Summary and Conclusions

• Nanoscience is the fabrication and study of objects ~1 to 100 nm.

• Things change when you get that small quantum mechanics

• Vast new opportunities for designing materials for new purposes!

Good web sites

• Nanoscale Informal Science Education (NISE) Network • http://www.nisenet.org/

• National Center for Learning and Teaching in Nanoscale Science and Engineering (NCLT) • http://www.nanoed.org/

• “When Things Get Small”: 30 min. TV show, 5 Emmy Awards!• http://www.uctv.tv/getsmall/

• “There’s Plenty of Room at the Bottom”, Feynman’s lecture from 1959• http://www.zyvex.com/nanotech/feynman.html

• Science in Motion (Pennsylvania)• http://www.science-in-motion.org/

• Profile of Naomi Halas• http://www.pbs.org/wgbh/nova/sciencenow/3209/03.html