Crystal forms gas-triggered switch

By Eric Smalley, Technology Research News

Crystals tend to crumble apart in the presence of reactive gases, but researchers at Utrecht University in the Netherlands have found a crystal that not only holds together but also changes color.

The process is reversible, meaning the crystals can be switched between clear and orange-colored states by adding or removing sulfur dioxide gas. The crystals are made of an organic compound that includes platinum.

The gas-triggered switches could be used as gas detectors and might even play a role in optical networks.

Molecules in a crystal are like bricks in an enormous wall, said Martin Albrecht, a graduate student researcher on the project. Ordinarily, chemical reactions change the size and shape of the bricks, causing the wall to fall apart.

The researchers found that when crystals made of an organoplatinum compound react with sulfur dioxide gas, the altered molecules immediately reorganize, maintaining the crystalline structure, Albrecht said.

"Removal of the gas causes the bricks to shrink again and the wall is regenerated in its

original form," he said.

Because the crystal also changes color, the two states can be readily observed and can serve as the on and off positions of a switch. The switches could be integrated into optical networks by devices that sense changes in color or by altering the color of light beams that shine through it.

"Light... may be charged with extra information when passing through this switch," said Albrecht.

However, it's unlikely that the gas-triggered switches could serve as optical switches themselves because they would not be able to switch at the very high rates required for data communications, said Seth Marder, a professor of chemistry and optical sciences at the University of Arizona.

"If you have to do something where the whole crystal changes and it's by [absorption], it's unlikely that you're going to have that occur extraordinarily fast," he said.

The work required to make the switches practical makes it difficult to estimate a timeframe, said Albrecht. The researchers are searching for a more practical gas than sulfur dioxide to use as a signaling agent, he said. Sulfur dioxide is difficult to work with because it is poisonous and turns into the highly corrosive sulfuric acid when it oxidizes.

Albrecht's colleagues were Martin Lutz, Anthony L. Spek and Gerard van Koten. They published their work in the August 31, 2000 issue of the journal Nature. The research was funded by Utrecht University and the Dutch Council for Chemical Sciences.

Timeline:   Unknown
Funding:   University, Government
TRN Categories:   Semiconductors and Materials
Story Type:   News
Related Elements:   Technical paper "Organoplatinum crystals for gas-triggered switches" in the August 31, 2000 Nature


November 29, 2000

Page One

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Virtual mic carries concert hall sound over 'net

Researchers ready radio-receiver-on-a-chip

Proton memory is ultracheap but slow

Crystal forms gas-triggered switch


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