July 27, 2004

Scientists at the University of Chicago say they've found a better way to measure a confounding property of microscopic high-tech particles called quantum dots, which are used in lasers, biological studies and other applications.

Quantum dots, which are also called nanocrystals, emit light in a rainbow of colors.

That's a useful thing in various high-tech settings. But their tendency to blink hinders their technological value.

''A quantum dot might blink for just a millionth of a second, or it might blink for 15 minutes,'' says Matthew Pelton, a research associate at U. of C.'s James Franck Institute. ''This is one of the problems we have to solve if we want to engineer the properties of materials, particularly semiconductor materials, on the nanoscale.''

Pelton found a way to measure the blinking that's simpler and faster. He reports his findings in the Aug. 2 issue of Applied Physics Letters with co-authors David Grier, now of New York University, and Philippe Guyot-Sionnest of the University of Chicago.

Grier compares the light output, or ''noise,'' of a blinking group of quantum dots to the babble of cocktail-party conversation. ''Even if everyone's talking about the same thing, you probably wouldn't be able to figure out what they're saying,'' Grier says. ''Matt has discovered that, for these blinking quantum dots, all the conversations are the same in a very special way. And that allows you to figure out an awful lot about what's being said by listening to the whole crowd.''

Pelton's method allows scientists to study the blinking patterns of large quantities of dots and do so in just a few minutes with standard laboratory equipment under a variety of environmental conditions.

''Many scientists are trying to start up companies to make nanocrystals and to find a new use for them,'' says Guyot-Sionnest.

Sun-Times news services