2023 Nobel Prize in Chemistry: three chemical giants connected by quantum physics

Two American scientists and a Russian scientist have been awarded the 2023 Nobel Prize in Chemistry for the discovery and synthesis of quantum dots - the discovery of which fueled the nanotechnology revolution.

The prize was split equally between Moungi Bawendi, Louis Brus and Alexey Ekimov for discovering the unique properties of nanomaterials and how they can be made, paving the way for a wide range of nanomaterials in consumer electronics, biochemistry and medicine. The Royal Swedish Academy of Sciences announced that the particles "have unique properties and can now spread light from TV screens and LED lights."

Quantum Dot Discovery Wins Nobel Prize in Chemistry

Quantum dots are tiny inorganic particles that emit colors ranging from red to blue when exposed to light. The color they emit depends on the size of the particle.

Scientists can design quantum dots from materials including gold, graphene and cadmium and create their colors by controlling their size. The tiniest particles, in which the electrons are most tightly packed, emit blue light. Slightly larger particles, in which the electrons bounce off longer wavelengths, will emit red light.

Quantum dots, sometimes called artificial atoms, are precise nanocrystals made of silicon and other semiconductor materials just a few nanometers wide, small enough to exhibit quantum properties like individual atoms-despite the fact that they are only a few hundred to a few thousand atoms in size. Because electrons can be trapped at specific energy levels within them, the nanocrystals can only emit light at specific wavelengths. By controlling the size of the particles, researchers can precisely set the color in which the quantum dots will blink when stimulated.

On the morning of October 4, Johan Åqvist, chairman of the Nobel Prize Committee for Chemistry, presented a series of five flasks at the Nobel Prize podium, each containing liquids that emit a different color. These liquids contain liquid solutions of quantum dots that are only a few millionths of a millimeter in size. At this tiny size, "quantum mechanics starts to play all sorts of tricks," says Åqvist.

Quantum effects occur when particles shrink. When the diameter of a particle is only a few nanometers, the space available for electrons shrinks; this affects the optical properties of the particle.

"It's been a long time since anyone could actually make particles this small. But this year's winners have succeeded." Johan Åqvist, chairman of the Nobel Committee for Chemistry at the Royal Swedish Academy of Sciences in Stockholm, said, "This achievement represents an important milestone in nanotechnology."

Heiner Linke, a member of the Nobel Committee for Chemistry and a professor of nanophysics, explained that quantum mechanics predicts that the wave function of an electron is compressed if it is squeezed into a small space. The smaller the space, the more energy the electron has, which means it can provide more energy to the photon. Essentially, the size of a quantum dot determines the color in which it shines: the smallest particles glow blue, while larger particles glow yellow and red.

By the 1970s, physicists knew that quantum phenomena should theoretically be associated with particles of very small sizes, just as they are associated with ultrathin films, but it seemed unlikely that this prediction would ever be verified: there seemed to be no good way to make and handle particles except by masking their properties in other materials. However, in 1981 at the S.I. Vavilov State Optical Institute in the USSR, Yekimov changed that. While adding compounds of copper and chlorine to glass, he discovered that the color of the glass depended entirely on the size of the added particles. He soon realized that quantum effects were likely the cause.

In 1983, Bruce conducted experiments at Bell Labs using light to drive chemical reactions. Bruce (now at Columbia University) noticed that even when nanoparticles were free-floating in a liquid solution, their size affected their optical properties. Link says, "This sparked a lot of interest."

The potential optoelectronic capabilities of such particles were not lost on technologists, who followed the lead of Yale's Mark Reed and called them quantum dots. But for the next decade, researchers struggled to precisely control the size and mass of these particles.

In 1993, Åqvist says, Bavendi invented an "ingenious chemical method" to make perfect nanoparticles. He was able to precisely control when the crystals formed and then stop and restart their further growth in a controlled way - a discovery that has led to the use of quantum dots in a wide range of applications.

Quantum Dot, make the "vision" more exquisite "color"

Today, quantum dots are commonly used in electronic displays and biomedical imaging. The fluorescent properties of quantum dot particles allow researchers to track drug delivery in the body and study the precise location and growth of tumors, among other things.

Quantum dots have now entered the mainstream market and are being used in television displays - a multimillion-dollar industry. Murray says that when he and Bavendi began their work, there was skepticism about whether it was worth funding the use of chemistry to control materials at such a small level; "now, it's great to see that the investment is paying off handsomely."

Now that producing quantum dots has become a fairly simple chemical process, Murray says, they can find many more applications: the ability to tune the interaction of particles with light, the ability to help engineers develop low-cost optical detectors and sensors ...... for example, which are an important component of autonomous transportation; and the ability to integrate quantum dots into materials with unique shapes, textures and densities.

Quantum computing employs a similar concept as a platform, with the aim of utilizing quantum phenomena to perform calculations that would be impossible with ordinary computers. Researchers can fabricate devices with quantum dot properties on silicon chips and then manipulate the spin of individual electrons captured within them. Lieven Vandersypen, a physicist at Delft University of Technology in the Netherlands, explains, "Both types of quantum dots are very small, and the confinement of an electron in a quantum dot leads to quantized orbitals, just like atoms."

However, quantum computing requires different quantum dots than those found in TV displays, says Sofia Patomäki, who recently earned her Ph. D. from University College London. Among other reasons, quantum dots for displays typically use chemical elements optimized for light in the visible spectrum, whereas quantum computing dots need to incorporate elements optimized for lower-energy light.

The Big Three of Chemistry Connected Through the Quantum Field

This time, Swedish media reported hours before Wednesday's press release from the Royal Swedish Academy of Sciences that Bavendi, Bruce and Ekimov were the latest Nobel laureates; public broadcaster SVT said they were awarded the prize for "the discovery and synthesis of quantum dots."

After the official announcement of the three winners, Secretary General Hans Ellergren said the Swedish Academy of Sciences would investigate how the information was leaked out in advance.

"A press release was issued for reasons that are not yet clear. This morning we were very active in finding out exactly what happened, which is very unfortunate and we deeply regret what happened." The academy awards prizes in physics, chemistry and economics and solicits nominations a year in advance from thousands of university professors and other scholars around the world.

The committee for each award discusses the candidates in a series of meetings and then presents one or more proposals to the entire academy for a vote. The results of the deliberations, including the names of nominees other than the winner, are kept confidential for 50 years.

Bavendi was born in Paris, France, in 1961 to a Tunisian father and a French mother. He immigrated to the U.S. with his family when he was ten years old, and although he excelled in science in high school, he failed his first college chemistry class at Harvard; but he persevered, earning an undergraduate degree and later a PhD. D. at the University of Chicago. He later joined Bell Labs and finally the Massachusetts Institute of Technology (MIT), where he remains a professor.

In a press conference, Bavendi said he was "very surprised, sleepy, shocked, surprised, and very honored." Asked about the leak, he said he didn't realize he had won the Nobel Prize until the academy called him. Bavendi said that when he started working on quantum dots, he didn't think about the possible applications of his work: "The real motivation was basic science. A basic understanding and curiosity about how the world works? -- that's what drives the work that scientists and academic scientists do."

Bruce worked at the legendary Bell Labs in the United States (then a hotbed of scientific discovery), conducting experiments involving chopping up particles to provide greater surface area and faster chemical reactions; during his work, he noticed that the optical and other properties of particles changed as the particles became smaller - something that could only be explained by quantum mechanics. Bruce stayed at Bell Labs for 23 years and is now a professor emeritus at Columbia University. He said he didn't pick up the phone when the Swedish Academy of Sciences called early in the morning to inform him.

The phone was ringing through the night, but I didn't answer it because I was basically sleeping," he told The Associated Press. When he woke up around 6 a.m., he finally saw the news online."

"I certainly didn't expect that." Bruce said he's happy to see the field of chemistry he works in recognized. He believes that practical applications of quantum dots, such as creating colors in flat-screen TVs, are what he hoped for when he started this work decades ago.

"It's hard to accurately predict the outcome of basic research; it's more about the knowledge base than the actual material. But in this case, it's both."

Yekimov is the former chief scientist of Nanocrystals Technology, a New York-based company he began working for in 1999. The Swedish Academy of Sciences credited him with proving in the early 1980s that the size of copper chloride nanoparticles affects the color of glass.

Yekimov told the Associated Press, "It's great that after 40 years of work we finally got this result." Yekimov was born in the former Soviet Union in 1945 and graduated from Leningrad State University; he published his findings in a Soviet scientific journal in 1981 and became the first person to intentionally create quantum dots.