1. Alejandro Galvan Mentors: Prof. Roger Dorsinville Alberto Tonizzo IUSL High School Summer Program Summer 2006

2. A Quantum Dot (semiconductor nanocrystal) contains discrete energy, much like an Atom. They are sometimes called “artificial atoms.” A quantum dot’s energy levels can be controlled by changing their size and shape and the depth of their potential. There are anywhere from 100 to 1,000 electrons in a quantum dot and their size ranges from 2 to 10 nanometers, or 10 to 50 atoms, in diameter. Atom Quantum Dot http://oemagazine.com/fromTheMagaz ine/oct02/images/quantumdotsill.jpg http://home.arcor.de/cybertaro/k osmologie/atom.jpg

3. Quantum Dot Contd. http://www.nanotech-now.com/images/QDot-nanocrystal-size.jpg An Atom ranges from0.1 to 0.5 nanometers (1 × 10 -10 m to 5 × 10 -10 m). A quantum dot ranges from 2 to 10 nanometers.

4. The larger the quantum dot, the redder the fluorescence, and the lower the energy of the emitted light. The smaller the dot, the bluer the fluorescence, and the higher the energy. Quantum dots have found their way into our homes. For example, the new Play Station 3 and HD DVD players both use a blue laser for data reading. http://en.wikipedia.org/wiki/Quantum_dot http://www.evidenttech.com/qdot-definition/images/08-tun.jpg

5. Reverse MicelleNormal Micelle H2OH2O Head: Hydrophilic Oil Tail: Hydrophobic H 2 O (Water)

6. We are using QDs (quantum dots) to find a new material that can absorb strong laser light frequency (optical limiting) making the light of the laser weak. This material can protect human eyes, devices etc. It is intensity dependent (i.e., the stronger the laser light the more the material absorbs). New Material (Filter) High Intensity Laser Light Low intensity Light (not harmful)

7. 1.In order to make this new material we are using a toluene dispersion of reverse micelles containing CdSe (Cadmium Selenide) quantum dots. Solvent: Toluene H 3 C (Molecular Formula: C 10 H 23 N) 2.This solution was put in a polystyrene matrix and also in a PMMA (polymethyl methacrylate) matrix to make a transparent film. 3.We are trying to fabricate (through the spin coating technique) thin films consisting of this mixture. In fact solution are not sufficient for device applications. NH 2

8. Solution of reverse Micelles and Toluene Quartz used to make the thin-film *1 drop/min. http://www.eng.uc.edu/~dshi/biomat404/lab_tour/Spin.jpg

9. Our Quantum Dot: Cluster or Quantum Dot NH 2 Micelles: are organic substances used to stabilize the Quantum Dot.

10. http://www.gmi-inc.com/Categories/cary5000.htm http://lma.in2p3.fr/Images/perkin2.jpg

11. Main absorption frequency * From the peak frequency you can calculate the size of the Quantum Dot 1.Scattering of Light 2.Low absorption Intensity

12. * From the peak frequency you can calculate the size of the Quantum Dot 2.Stil some scattering of Light Main absorption frequency 1.Very low absorption Intensity

13. Results: We did see some absorption at 415 nm which indicated the presence of a stable Cadmium Selenide quantum dot. However the preparation methods used (Polystyrene [50mg/ml], PMMA (polymethyl methacrylate [50mg/ml]) did not result in a transparent film due to scattering of light. Ideally we would like a transparent film so that our quantum dot can be more frequency specific in terms of being used as a filter.

14. Further Work: Preparation of CdSe QDs capped in micelles made of different alkyl amines (i.e., octadecylamine instead of decylamine).Fabrication of thin films out of this dispersion are anticipated to be more transparent and present a long range order (hexagonal lattice).

15. Mentors: Prof. Roger Dorsinville Alberto Tonizzo IUSL High School Summer Program N.A.S.A./C.O.S.I. The Harlem Children Society