"A trio of scientists won the Nobel Prize in chemistry for work on quantum dots, tiny particles that add color to screens and medical procedures.
The Nobel committee said Wednesday that Moungi Bawendi, Louis Brus and Alexei Ekimov won the chemistry prize for research on the dots, semiconductor particles just a few nanometers in size. They have been integrated into TV screens and help guide surgeons as they remove tumor tissue.
Researchers hope quantum dots can eventually help develop flexible electronics, thinner solar cells and encrypted communication.
Ekimov and Brus independently discovered it was possible to make quantum dots; Bawendi revolutionized their production. Before their work, few people thought effects that could theoretically arise in nanoparticles would ever be put to practical use.
"For a long time, nobody thought you could ever actually make such small particles," said Johan Aqvist, chair of the Nobel committee for chemistry.
Quantum dots are now mass manufactured, making lights more energy efficient and producing precise colors on electronic devices. Biochemists use the dots to map cells and organs.
Bawendi is a chemist at the Massachusetts Institute of Technology, and Brus is affiliated with Columbia University. Ekimov, a Russian physicist, works at New-York based Nanocrystals Technology.
Quantum dots are so small that properties including color depend on their size, even if their chemical makeup is the same. The smallest shine blue, while larger dots emit yellow and red. That is because the electrons squish together when a particle is shrunk, giving them more energy and causing the dots to emit different wavelengths of light. Other properties including the melting point also change.
"The materials are very bright, and very well color-defined," said Rigoberto Castillo Advincula, a nanomaterials researcher at the University of Tennessee and Oak Ridge National Laboratory. They can be more expensive than other materials, Advincula said, but also produce more light.
Some predicted as early as the 1930s that such an effect could occur, but Ekimov, studying colored glass, was the first to demonstrate it, in the early 1980s. Ekimov was interested in the fact that a single substance could create different colored glass. He produced tinted glass and X-rayed it.
Tiny crystal particles had formed in the glass, and the color of light the glass absorbed depended on their size. The physicist realized he had observed the quantum effect. Ekimov published in a Soviet journal.
Brus was unaware of the discovery when he made a similar one at Bell Laboratories in the U.S., where he was working with light-capturing particles floating in a liquid. He noticed that the particles' optical properties changed after leaving them on a lab bench, potentially because they grew. He produced even smaller particles and saw the same effect as Ekimov.
Brus slept through a call from the Nobel committee, he said. He woke up after the phone kept ringing and called one number back. It was a TV station in Miami, asking for his reaction to winning the prize.
Even after the twin discoveries, it was difficult to control the size of the particles, and their quality was often unpredictable. Bawendi, who trained in Brus's laboratory, wanted to solve that problem.
Bawendi had a breakthrough in 1993 at MIT, when his group injected substances that would form the tiny crystals into a heated liquid. Changing the solution's temperature could change the size of the crystals.
"To understand the physics, which was the motivation, we had to create the material," Bawendi said. "I would never have thought that you could make them at such a large scale and that they would actually make a difference in the consumer area."" [1]
1. U.S. News: Quantum Dot Researchers Win Chemistry Nobel. Abbott, Brianna. Wall Street Journal, Eastern edition; New York, N.Y.. 05 Oct 2023: A.2.
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