By Genevieve Ko
The Nobel Prize in chemistry was awarded Wednesday to Moungi G. Bawendi, Louis E. Brus and Alexei I. Ekimov for being pioneers of the nanoworld. The new laureates discovered and developed quantum dots, semiconductors made of particles squeezed so small that their electrons barely have room to breathe.
Semiconductors are crystals that help power our electronics. But while traditional crystals may be quite large at the molecular level, a quantum dot consists of just a few thousand atoms squished into a space just a few nanometers across. The difference in size between a quantum dot and a soccer ball is about the same as the difference between a soccer ball and the Earth, the Nobel Foundation said.
“For a long time, nobody thought you could ever actually make such small particles,” Johan Aqvist, the chair of the Academy’s Nobel committee for chemistry, said at a news conference announcing the 2023 laureates. Presenting the topic with five colorful flasks lined up in front of him that he said contained quantum dots in a liquid solution, he said: “But this year’s laureates succeeded.”
The news of the laureates’ expected win had been reported earlier Wednesday morning in the Swedish news media, a highly unusual leak that was then reported by Reuters and The Associated Press several hours before the official announcement by the Royal Swedish Academy of Sciences, which awards the prize.
The Swedish news outlets cited what they said was an email from the academy that had been mistakenly sent early. Reuters quoted Aqvist as saying, “It is a mistake by the Royal Swedish Academy of Sciences.” He noted that the committee’s meeting was due to start at 9:30 a.m. local time (3:30 a.m. Eastern) and added, “so no decision has been made yet. The winners have not been selected.”
Who are the winners?
Bawendi, born in 1961 in France, is a professor at the Massachusetts Institute of Technology, and used to study under Brus as a postdoctoral researcher.
Brus, born in 1943 in Cleveland, is a professor emeritus at Columbia University.
Ekimov, born in 1945 in the former Soviet Union, was previously the chief scientist at Nanocrystals Technology, a company based in New York.
Why did the committee say they received the prize?
Electrons exist at fixed distances from an atom’s nucleus, with higher energy levels corresponding to greater distances. When atoms get energized, their electrons temporarily jump to greater distances and higher levels. When they fall back down, the electrons release the extra energy as light.
A basic principle of quantum mechanics is that objects can behave like particles or like waves. The same holds true for electrons: Like other types of waves, they have a frequency that relates to the color of light they release. Scientists have known since the 1930s that squeezing atoms into a tiny enough “container” could increase the frequency of their electrons and change the type of light the material absorbs or emits. That container is a crystal, called a quantum dot because it triggers the wavelike behavior theorized by quantum mechanics.
But that thought stayed theoretical, because scientists didn’t know how to squeeze a material to the point where such quantum effects would take over. In the 1970s, Ekimov began studying how colored glass could differ in hue depending on how long it was heated. He found that when heated, copper chloride crystals formed inside the glass. The smaller the crystals, the bluer the glass appeared. Independently, Brus discovered the same effect using cadmium sulfide crystals.
These were the first observations of a quantum effect that depended on size, rather than the elemental makeup of the material. Still, scientists had to figure out how to control this effect to harness it for real-world applications.
In the 1990s, Bawendi figured out how to produce quantum dots that had superb optical quality. They had to be made in solution “with exquisite control of their size and surface,” Aqvist said. Bawendi, he added, invented an ingenious chemical method “for doing just this.” The breakthrough revolutionized technology in medicine and our everyday electronics.
Quantum dots are now used to tune the colors in LED lights and increase the resolution of television screens. They can also be used as fluorescent imaging tools in biomedical applications, such as identifying cancerous tissue. Quantum dots are expected to lead to advances in electronics, solar cells and encrypted quantum information.
What did the laureates say about winning the prize?
Bawendi said he was “sound asleep” when he got the call.
“I wasn’t sure it was true,” he said in an interview with the Nobel Foundation. “It’s quite an honor and quite a surprise.”
He added that the honor was complemented by sharing the prize with his former mentor, Brus. “He molded me as a scientist,” Bawendi said.
Before the announcement, Bawendi was scheduled to teach a 9 a.m. class on introductory quantum mechanics at MIT. But the lesson ended up being about his career leading up to the Nobel Prize. Of the day’s chaos, he said, “I’m just going to let it ride.”
Ekimov described feeling a bit disoriented when he heard the news, and his satisfaction that the work was being recognized. He recalled learning about quantum mechanics as a young student two decades before the observations that led to the Nobel Prize. “It was not surprising,” he said of the discovery, adding that it had been their hope “to make an experimental confirmation” of the already well-established theory.
Brus said in an interview that his phone had kept ringing as he tried to sleep. When he finally called back, he found out from a Miami TV station that he had won the Nobel. Then he checked online to make sure it wasn’t a prank.
“I had forgotten that today is the chemistry Nobel Prize day,” said Brus, who added that it “feels surreal.” His first thoughts were of the many collaborators who helped realize the discovery. “I represent a big community who worked on this,” he said.
When the fanfare dies down, Brus plans to celebrate with his family. “They’re just jumping up and down, as you can imagine,” he said.