Roland Piquepaille's Technology Trends
How new technologies are modifying our way of life

samedi 17 juillet 2004

A team of chemists from Lawrence Berkeley National Laboratory (LBNL), working with computer scientists, has discovered a new kind of adaptable nanoscale compounds. They previously devised tetrapods, structures with four 'arms' or 'legs', from materials such as cadmium telluride. But they now found that by using different materials, like selenium, tellurium or sulfur, to produce crystals of different cadmium compounds, each 'leg' could acquire different electronic properties. After isolating these 'legs,' they were able to produce 'nanorods' with specific properties. In "Nanotech Branches Out with New Discovery," NewsFactor Network says that this discovery will have important consequences, leading to the development of new solar cells, quantum computers or simply very small and fast transistors.

Here is the introduction of this article.

Researchers at Lawrence Berkeley National Laboratory have discovered a new class of nanoscale compounds that have individually tunable branches. The discovery could lead to the development of super-accurate electronic devices, including quantum computers.

Here is an image showing you the kind of nano tetrapods built at LBNL.

Nano tetrapods developed at LBNL "Examples of nanostructures made possible by the Alivisatos group's new method include tetrapods of cadmium selenide (left) extended with segments of cadmium telluride (upper right), which can be made to branch in turn (lower right)." (Credit for image and legend: Link at LBNL).

For more technical information about this discovery, you might want to read this article of Betterhumans, "Nanostructures Calculated to be Useful." Here are some short excerpts.

Berkeley researchers had previously created nanoscale tetrapods with four branching rods. They then set about making tetrapods and other branching structures in a way that could allow investigation of their potential applications, aiming to produce structures coupled with controlled height and width and arranged at well-defined angles and distances.
For this they used suspensions that included cadmium, selenium, tellurium, sulfur and other constituents to produce crystals of different cadmium compounds. Cadmium is used in such electronic applications as batteries and semiconductors. Structures begin with a quantum dot. Quantum dots are assemblies of hundreds or thousands of atoms in which it's possible to control a single electron.
Berkeley researchers got the dots to sprout four arms to form a tetrapod, which can be lengthened into nanorods containing segments of different compounds."Now you've effectively got four quantum rods coupled electronically with the central quantum dot," says postdoctoral fellow Yi Cui. "These coupled quantum systems might be useful in quantum computation."

Please read the whole article for more details.

And note that the research work from Paul Alivisatos, director of the Materials Sciences Division at LBNL, and his colleagues, has been published by the Nature journal, under the title "Colloidal nanocrystal heterostructures with linear and branched topology." Here is a link to the abstract, which is not really written in plain English, so it's up to you to go and read it.

Finally, you might want to read a previous post about Alivisatos's research, "Nanotech solar cells: Portable Plastic Power."

Sources: Mike Martin, NewsFactor Network, July 16, 2004; ; Gabe Romain, Betterhumans, July 7, 2004; Lawrence Berkeley National Laboratory news release, July 7, 2004; Nature 430, 190 - 195, July 8, 2004

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