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Reverse Micellar Synthesis of Cadnium Selenium (CdSe) Quantum Dots(QDs)

Reverse Micellar Synthesis of Cadnium Selenium (CdSe) Quantum Dots(QDs). Alejandro Galvan Mentors: Prof. Roger Dorsinville Alberto Tonizzo IUSL High School Summer Program Summer 2006. Understanding What is a Quantum Dot?.

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Reverse Micellar Synthesis of Cadnium Selenium (CdSe) Quantum Dots(QDs)

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  1. Reverse Micellar Synthesis of Cadnium Selenium (CdSe) Quantum Dots(QDs) Alejandro Galvan Mentors: Prof. Roger Dorsinville Alberto Tonizzo IUSL High School Summer Program Summer 2006

  2. Understanding What is a Quantum Dot? A Quantum Dot (semiconductor nanocrystal) contains discrete energy, much like an Atom. They are sometimes called “artificial atoms.” Quantum Dot Atom http://home.arcor.de/cybertaro/kosmologie/atom.jpg http://oemagazine.com/fromTheMagazine/oct02/images/quantumdotsill.jpg • 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.

  3. Quantum Dot Contd. • 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. http://www.nanotech-now.com/images/QDot-nanocrystal-size.jpg

  4. Other Features: • 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. http://www.evidenttech.com/qdot-definition/images/08-tun.jpg http://en.wikipedia.org/wiki/Quantum_dot 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.

  5. Understanding Micelles Head: Hydrophilic H2O (Water) Oil Oil H2O Tail: Hydrophobic Reverse Micelle Normal Micelle

  6. Objective: New Material (Filter) High Intensity Laser Light 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). Low intensity Light (not harmful)

  7. The Experiment 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 • H3C NH2 (Molecular Formula: C10H23N) 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.

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

  9. Micelles: are organic substances used to stabilize the Quantum Dot. Our Quantum Dot: NH2 Cluster or Quantum Dot

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

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

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

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

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