The 2023 Nobel prize in chemistry was jointly awarded to Moungi Bawendi, Louis Brus, and Alexei Ekimov for the discovery and developments of quantum dots. These nanoparticles are so small that their size determines their properties. Quantum dots can be found in modern computers, televisions, and LED lights, among numerous other applications.
Bawendi is a professor at the Massachusetts Institute of Technology, Brus is a professor emeritus at Columbia University, and Ekimov works for a company called Nanocrystals Technology in New York State.
“For a long time, nobody thought you could ever actually make such small particles,” Johan Åqvist, chair of the Nobel Committee for Chemistry, said during a news conference. “But this year’s laureates succeeded.”
Size matters in the nanoscale
Quantum dots are among the smallest components of nanotechnology. Typically, an element’s properties are governed by how many electrons it has. When that matter shrinks down to nano-dimensions quantum phenomena arise. This means the element’s properties are now governed by the size of the matter instead of the number of electrons it has.
Quantum dots are made of only a thousand atoms. By comparison, one quantum dot is to a soccer ball as a soccer ball is to the planet Earth.
The quantum dots that Bawendi, Brus, and Ekimov produced are particles small enough for their properties to be determined by quantum phenomena. They are among the smallest, but most important particles, nanotechnology.
“Quantum dots have many fascinating and unusual properties. Importantly, they have different [colors] depending on their size,” Åqvist said in a statement.
The movement of electrons in quantum dots is highly constrained. This then affects how they absorb and release visible light, allowing for very bright colors. The quantum dots themselves are nanoparticles that glow red, blue, or green and the color depends on the size of the particles. Larger dots shine red and smaller dots shine blue. The change in color depends on how electrons act differently in more confined or less confined spaces.
Big discoveries, super small particles
In 1937, physicists theorized that size-dependent quantum effects could arise in nanoparticles. However, it was almost impossible to sculpt in nano dimensions, so few believed that it was possible.
During the early 1980s, Ekimov created size-dependent quantum effects in colored glass. The color of the glass came from the nanoparticles of copper chloride. With this colorful experiment, Ekimov demonstrated that the particle size affected the color of the glass via quantum effects.
A few years later, Brus became the first scientist in the world to prove that size-dependent quantum effects in particles were floating freely in a fluid. Brus and Ekimov were actually working independently from one another when they made their initial discoveries.
In 1993, Bawendi revolutionized the chemical production of quantum dots. His techniques resulted in almost perfect particles, which was necessary for using the quantum dots in a wide range of applications.
Quantum dots can now be found in computer monitors and television screens and even help biochemists and surgeons map tissues and remove tumors.
Last year’s chemistry prize was also awarded to a trio of chemists: Carolyn R. Bertozzi for her work in bioorthogonal chemistry alongside K. Barry Sharpless and Morten Meldal for laying the foundation for click chemistry.