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Synthesis of Quantum Dots

Synthesis of Quantum Dots. Presentation By: Melissa Schillo Advised By: Dr. Shih. What are quantum dots (QDs)?. Nanoparticles Semiconductor crystals Quantum confinement effect. Picture courtesy of QuantumDot Technology. Nano(meter): extremely small; one-billionth of a meter (10 -9 )

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Synthesis of Quantum Dots

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  1. Synthesis of Quantum Dots Presentation By: Melissa Schillo Advised By: Dr. Shih

  2. What are quantum dots (QDs)? • Nanoparticles • Semiconductor crystals • Quantum confinement effect Picture courtesy of QuantumDot Technology Nano(meter):extremely small; one-billionth of a meter (10-9) Crystal:A homogenous unit cell formed by a repeating, three-dimensional pattern of atoms, ions, or molecules and having fixed distances between constituent parts Picture courtesy of Evident Technologies

  3. Properties of a Semiconductor Conduction Band FreeElectron Excited Electron Band Gap Eg Hole ...How does this effect color? Valence Band Photon Emitted Photon Absorbed

  4. Quantum Confinement Effect: Color and Luminescence Band gaps of Bulk Solids Pictures courtesy of www.qdots.com Broad range of colors

  5. Picture courtesy of Science Magazine April 2003 Biological Imaging Green quantum dots cling to mitochondria in the cytoplasm; orange ones label proteins in the same cells' nuclei. Red quantum dots injected into a live mouse mark the location of a tumor. Picture courtesy of Science Magazine April 2003

  6. Picture courtesy of QuantumDot Technology Research Goals: • Stability of QDs • Produce a spectrum of colors

  7. Disadvantages: • Complex process • Environmentally unfriendly • Expensive How are QDs made? • Process of OTHER Groups: • Use organic solvent Trioctylphosphine oxide (TOPO) • Prepare two separate solutions • Me2Cd in TOP • Sulfur in TOP • Mix two solutions • Inject mixture into TOPO • Quench mixture—by controlling time, there are different sizes • Remove quantum dots and place in aqueous solution • Advantages: • Injection method controls nucleation • Temperature controls growth • Core-Shell increases quantum yield • and makes intensity better

  8. How are QDs made? • Process of OUR Group: • Use aqueous solution (DI water) • Use only one step • Advantages: • Simple process • Environmentally friendly • Cost effective

  9. 2 6 3 5 Periodic Table courtesy of ChemGlobe How are QDs made?

  10. PbS PbS CdS CdS CdS ZnS How are QDs made? CdS Cd(NO3)2 + Na2S  CdS + 2Na+2 + 2NO3- PbS Pb(NO3)2 + Na2S  PbS + 2Na+2 + 2NO3- Zn(NO3)2 + Na2S  ZnS + 2Na+2 + 2NO3-

  11. Quantum Dot Samples in UV Light Cadmium Sulfide (pH7, pH10) Three variations of the Pb:Cd 1:9 ratio ZnS coated CdS; Cds CdS, Pb:Cd 1:9, PbS

  12. Picture courtesy of stardec.ascc.neu.edu Stabilize Ammonia 4 A Sonicate

  13. Problems and Possible Solutions: • Broad white band in photoluminescence emission spectra • Large particle size variation OURS IDEAL Picture courtesy of Quantum Dot Corporation

  14. Conclusion: • Successful in making orange- • red colored quantum dots • Future work will be to narrow • the particle distribution and • make a smaller particle size

  15. Acknowledgements: Dr. Wei-Heng Shih Dr. Wan Shih Hui Li David Zimmerman DREAM Dorilona Rose Engineering Department

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