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Quantum Dots  ©

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From 12/01/2014 through 11/9/2010

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Notes

Quantum dots is one of those new developments which brings the idea of nanoparticles to a new level.  It means active particles which can be programmed in a simple way to do and control things.  This is a WoW! development.  (RDC 8/26/2011)

“A quantum dot is a semiconductor whose excitons are confined in all three spatial dimensions. Consequently, such materials have electronic properties intermediate between those of bulk semiconductors and those of discrete molecules. They were discovered at the beginning of the 1980s by Alexei Ekimov in a glass matrix and by Louis E. Brus in colloidal solutions. The term ‘quantum dot’ was coined by Mark Reed.

“There are colloidal methods to produce many different semiconductors. Typical dots are made of binary alloys such as cadmium selenide, cadmium sulfide, indium arsenide, and indium phosphide. [However], dots may also be made from ternary alloys such as cadmium selenide sulfide. These quantum dots can contain as few as 100 to 100,000 atoms within the quantum dot volume, with a diameter of 10 to 50 atoms. This corresponds to about 2 to 10 nanometers, and at 10 nm in diameter, nearly 3 million quantum dots could be lined up end to end and fit within the width of a human thumb.”

(Wikipedia, Quantum Dots, 11/9/2010)

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“Biologists use fluorescent particles for the visualization and tracking of cells and proteins; generally, the brighter the particle the better. Quantum dots are the brightest colloidal particles available. Nanometer-sized semiconductor crystals, they shine brighter and longer than other fluorescent particles.”

“However, quantum dots have their limitations, especially when used for biological applications. They can be instable in aqueous environments and are subject to “blinking” or flickering. But perhaps the greatest drawback is their potential toxicity. They are made from alloys such as cadmium selenide or indium arsenide that could be broken down releasing toxic ions.”

“On the other hand traditional fluorescent materials such as organic dyes are not as bright as quantum dots and suffer from photo-bleaching. Igor Solokov and coworkers have used an inorganic silica shield to prevent the photobleaching of organic dyes. Using sol/gel assembly, they trapped the organic dyes inside a silica matrix, creating particles of the size of 20-50 nm. They found that the relative brightness of a single particle is equivalent to that of up to 770 free dye molecules or up to 39 quantum dots. Moreover, the particles were stable for at least 120 days.”

(Materials Views, Hiliary Gallagher, Quantum Dots, 6/14/2011)

YouTube Videos: Quantum Dots

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In this day of overworked technical people, keeping up is nearly impossible.  Maro's mission is to help keep up in as little time as possible.  Bookmark this page and check it often.  You will be surprised what can be picked up in just a few moments spent each day.

These pages list the links as they are found.  Some will abstracted and added to Maro Topics. (RDC 2/7/2012)

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Roger D. Corneliussen
Editor
www.maropolymeronline.com

Maro Polymer Links
Tel: 610 363 9920
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E-Mail: cornelrd@bee.net  

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Copyright 2012 by Roger D. Corneliussen.
No part of this transmission is to be duplicated in any manner or forwarded by electronic mail without the express written permission of Roger D. Corneliussen
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* Date of latest addition; date of first entry is 4/25/2012.

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