Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Bubbly Channels

Abstract:
Two-phase chip reactor for the production of very homogeneous nanoscopic semiconductor crystals

Bubbly Channels

June 29, 2005

Luminescent quantum dots of semiconducting materials could eventually help to identify tumors, illuminate large flat-panel monitors, or make optical data processing a reality. Quantum dots are nanoscopic crystals so small that their chemical properties are similar to those of individual molecules. Researchers at MIT have now developed a microfluidic technique that delivers tiny crystals of particularly uniform size - and thus excellent optical quality.

Cadmium selenide quantum dots are usually obtained by injection of precursor compounds into a hot solvent. Many factors, including local temperatures in the reaction vessel, concentration gradients, as well as the rates of mixing and the final cooling process, substantially influence the results, but are difficult to control. Relief is promised by microfluidic technology, a miniature reactor system made of long, very narrow channels on a platform in the form of a chip. The extremely small dimensions allow for very exact control of substance and heat transport. Conventional microfluidic reactors have drawbacks, however. The reactants diffuse slowly. In addition, the particles do not move through the channels at the same speed; those in the middle move faster than those alongside the slowing channel walls. The resulting nanocrystals thus spend different amounts of time in the reactor. These two phenomena lead to quantum dots with a wide range of diameters.

It shouldn't have to be this way, thought the team of scientists headed by Moungi G. Bawendi and Klavs Jensen. The solution: a two-phase microfluidic system in which gas bubbles divide the stream of liquid in the channels into individual, very regular segments. Within these segments, back-mixing results in a constant exchange of material between the walls and center of the channels - all particles spend roughly equal time in the reactor. In addition, in order to accelerate the diffusion of the reactants, the mixing zone of the channel is made with tight curves. The subsequent reaction zone reaches the necessary high temperature of 260 °C and is thermally isolated from the third zone, in which the reaction is stopped at temperatures under 70 °C. With their microfluidic reactor, the researchers attain quantum dots of uniform size in significantly higher yields than with previous microfluidic techniques. In addition, reaction times can be shortened without lowering yields - an important criterion for commercial processes.

####

About John Wiley & Sons, Inc.:
Founded in 1807, John Wiley & Sons, Inc., provides must- have content and services to customers worldwide. Our core businesses include scientific, technical, and medical journals, encyclopedias, books, and online products and services; professional and consumer books and subscription services; and educational materials for undergraduate and graduate students and lifelong learners. Wiley has publishing, marketing, and distribution centers in the United States, Canada, Europe, Asia, and Australia. The company is listed on the New York Stock Exchange under the symbols JWa and JWb.

For more information, please visit www.wiley.com

Contact:
Amy Molnar
201-748-8844
amolnar@wiley.com

Copyright John Wiley & Sons

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

Possible Futures

Scientists discover new 'boat' form of promising semiconductor: GeSe Uncommon form attenuates semiconductor's band gap size March 23rd, 2017

Rare-earths become water-repellent only as they age March 22nd, 2017

Pulverizing e-waste is green, clean -- and cold: Rice, Indian Institute researchers use cryo-mill to turn circuit boards into separated powders March 21st, 2017

Electro-optical switch transmits data at record-low temperatures: Operating at temperatures near absolute zero, switch could enable significantly faster data processing with lower power consumption March 20th, 2017

Nanomedicine

Nanoparticle paves the way for new triple negative breast cancer drug March 20th, 2017

Block copolymer micellization as a protection strategy for DNA origami March 17th, 2017

Nanocages for gold particles: what is happening inside? March 16th, 2017

Biophysicists propose new approach for membrane protein crystallization March 8th, 2017

Announcements

Scientists discover new 'boat' form of promising semiconductor: GeSe Uncommon form attenuates semiconductor's band gap size March 23rd, 2017

Caught on camera -- chemical reactions 'filmed' at the single-molecule level March 22nd, 2017

Rare-earths become water-repellent only as they age March 22nd, 2017

Pulverizing e-waste is green, clean -- and cold: Rice, Indian Institute researchers use cryo-mill to turn circuit boards into separated powders March 21st, 2017

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project