By John Carroll
Small Times Correspondent

Aug. 14, 2001 — Scientists at the University of Texas at Austin are engaged in talks to either launch a start-up company or license the use of a breakthrough in nanocrystals that may lay the foundation for a new line of super small tech products.

“Things are moving real quick,” said Brian Korgel, an assistant


Brian Korgel, left, and Keith Johnston of the
University of Texas at Austin are looking into
products based on their method of producing
silicon-based nanocrystals in bulk.
professor at UT Austin’s college of engineering. “There are several things going on.” And in preparation for starting a new venture, Korgel and his associates are conducting a market study and patent search to clear the path for new product development.

Korgel and chemical engineering professor Keith Johnston have found a method to make stable microscopic nanocrystals out of silicon that can emit light. And by toying with the size of the silicon nanostructures, they can change the color of the light that shines through.

By creating a light-emitting silicon crystal, the researchers are opening the door to a new, nanosized material that can offer a much cheaper substitute for manufacturers needing light emitting diodes (LEDs) and pushing forward the work of scientists focused on creating nanosized devices that can be used as microscopic sensors or to help power computers.

What we’re trying to do is make some devices using our material,” said Korgel. “There are a lot of companies interested in using these small silicon particles to store an electrical charge for computer memory,” he added. “It can make essentially faster memory and generate less heat and radiate less power.” And while other companies have filed various patents for nanocrystals in the past, the UT Austin researchers’ production methods will make it easier to create the material in bulk at lower cost, they said.

Korgel’s achievement in making nanocrystals out of silicon using a method that will provide bulk quantities “is likely to have technological importance,” said Naomi Halas, professor of electrical and computer engineering at Rice University in Houston. While the UT Austin’s efforts won’t have direct impact on her own work exploring the optical qualities of nanocrystals, “it’s wonderful work. Extremely high quality work.”

Korgel and Johnston are also exploring ways that nanocrystals can be used to create a new generation of computer and television screens with the full rainbow of natural colors and possibly come up with new biomedical techniques.

Current cellular research has relied on dyed molecules for some of their work, Korgel said. But now he wants to learn whether nanocrystals can be used in place of the dyes.

One of the big advantages behind such a medical use, Korgel said, is that silicon is a very stable material. “It doesn’t react very easily.” That would make it inherently safer. “Putting cadmium into people doesn’t sound so great,” he said.

For decades, silicon has been the cheap raw material used in the transistors behind the amazing growth of computer power. But without the ability to emit light, developers had to turn to costly semiconductors when creating LEDs needed for products like lasers or computer and television screens.

Other scientists have made nanocrystals out of silicon over the past decade, but Korgel said they always found that the microscopic material was notoriously unstable, automatically reshaping itself into larger sizes.

Korgel has concentrated his work on breaking down silicon into tiny crystals and then manipulating the size of the crystals so they will emit different colored lights. Researchers heat a mix of an organic solvent called hexane and a hydrocarbon ligand known as octanol to 450 degrees Celsius inside a titanium chamber. Then they add silicon, which is broken down into spherical nanocrystals, also called quantum dots.

By combining the mix of agents, they are able to stop the silicon crystals from banding back together. The critical point in their success came when they found how to manipulate the size of the crystals by increasing and decreasing the concentration of ligands – a process that coats the silicon crystals to control their size.

As they reduce the size of the crystals, Korgel and others are able to create a crystal that emits a blue light. By making it larger, the crystal emits green light. And by making it larger still, the nanocrystals emit a red light.

After the solvent is removed from the mix, they harvest the crystals for use.

“You’re using the same material to create different colors,” Korgel said. “That’s why the nanostructures are so neat.” Currently, anyone trying to emit colors has to use a unique set of materials for each color.

The researchers’ progress with silicon nanocrystals — and its commercial potential — quickly attracted the attention of the venture capital field. Korgel said that he expects to hammer out the shape of a new venture by the end of the year.

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