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Nano Building Made Easy

A surprising array of nano structures can be formed by a new general self-assembly method.
January 5, 2006

For quite a while, researchers have been trying to develop novel ways of controlling the structure of materials on the scale of a few billionths of a meter – the size of large molecules. Such an achievement could lead to materials with exotic properties, or ways to fabricate computer processors to be much smaller and faster than current ones.

Building structures at this scale, however, typically involves slow and expensive methods of synthesis. Now researchers at IBM Research, in Yorktown Heights and Columbia University, have published findings in the current issue of Nature showing that a surprising range of nanostructures can be fabricated using a new self-assembly method.

“Nobody expected so wide a range of structures,” says Dmitri Talapin, a IBM researcher on the project. [Click here to see photos of some of these nano structures.] ”When we began this work we expected to observe three [structures]. We invested half a year before we were able to make the first structure. Since then we’ve had a couple of new structures every month. Now we have close to twenty – and we still see no limits.” Talapin believes they could easily see ten times this many structures, and that the process they use could be orders of magnitude less expensive than current fabrication methods.

The process depends on the ability to make uniform nanocrystals, something researchers have learned how to do well in the last few years. Once these crystals have been made, the IBM researchers found, it’s possible to mix them together to produce novel structures.

Nanocrystals that emit light at certain wavelengths, for example, can be combined with magnetic particles. The researchers showed that the two materials then could be arranged into an orderly array, called a superlattice, resulting in a structure that could exhibit a combination of these important properties – as well as others. Future applications, for instance, could include new materials for more efficiently converting heat and light directly into electricity.

The possibilities are wide ranging, according to Stephen O’Brien, a materials scientist at Columbia University, who says the ability to combine materials in this way should “spark a lot of imagination about things you could potentially do.”

“These are completely new materials that have never been seen before,” says Louis Brus, a chemistry professor at Columbia (who did not work on the project). What’s more, the potential for more materials is great, he adds. While Brus emphasizes that the paper describes basic research, it will, he says, “change the direction of other peoples’ work.”