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RE: Bottles of dots?

Posted by 6bq5 (A) on May 31, 2011 at 12:26:01

In Reply to: RE: Bottles of dots? posted by geoffkait on May 29, 2011 at 14:09:35:

The fabrication that we supported were done a relatively small scale; however at 8-12 nanometers in diameter, the dots themselves were even smaller. The 'bluer' the emission the smaller the diameter. To excite the dots,you need a light that is 'bluer' than the dot's emission. A Red(~600nM)Laser could not excite a 525 nM emitting Q-dot(r); however a Violet (405nM)laser could excite all the colors that we produced.
The 'tuning' of the color was actually a function of the time that the reaction was allowed to run - the 525nM dots 'nucleated' in under 30 seconds, and the 655 dots took ~10 minutes. Most of the visible spectra could be synthesized from Cadmium-Selanide materials, and we added tellurium to go into the infrared. We allso added a Zinc-Sulfide outer layer to 'passivate' the structure - making it more stable, and less prone to oxidization. These materials up to this point in the fabrication we Hydrophobic.
There are other metals in this region of the periodic table that theoretically should/could work; however there were a number of practical constraints. Most of the impediments came from what we called 'Lattice Miss-Match' where the structure of the atoms in the 'core' of the dot would not always form spheres, and did not provide a surface for the passivation layer to bond to the entire surface. The other issue that came up was the toxicity of the metals and the formats that the metals were available in(metal salts, and pyrophoric versions- diethylzinc...).

As to the opacity - the 655 nM materials were so efficient at being band-gap generators, that they would absorb most of the available light, additionally these were VERY concentrated solutions - we measured these in Molar units, not be volume or mass...Some of the bottles, were 500mL size, and we had LOTS of them.
Happy Listening

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