"Quantum Dots"

Chemistry
Louis E. Brus
Samuel Latham Mitchill Professor, Department of Chemistry, Columbia University, New York, NY USA

Brus is suggested as a possible Nobel Prize winner “for the discovery of colloidal semiconductor nanocrystals (aka quantum dots)”

It falls to few chemists to discover a previously unknown territory in the world of science, but that is just what Louis Brus did in the 1980s. He was a researcher at AT&T Bell Laboratories, New Jersey, and revealed his discovery in two papers published in 1983 and 1984. (Journal of Chemical Physics, 79[11]: 5566-71; and 80[9], 4403-9). These concerned the electronic behavior of what Brus called “small semiconductor crystallites.” Today these crystallites are referred to as semiconductor nanocrystals and are popularly referred to as “quantum dots.” Although these are clusters of hundreds and thousands of atoms, they exhibit discrete electron energy levels as if they were a single atom.

Together, the two key papers by Brus have been cited more than 3,500 times and have led to what is now a major field of scientific research, with applications as diverse as computing, biology, and even medical diagnostics. The optical aspects of quantum dots are the most noteworthy, with implications for LEDs.

Brus was looking at the behavior of colloidal particles of semiconductors, having chosen this form of matter because it maximized surface area. What he discovered, and what was unexpected, was that the minimum band gap was not a fixed quantity but varied. This is the energy required to promote an electron to a level at which it can escape the control of its parent atom. He deduced that this was linked to the size of the cluster of atoms — the smaller this was, the more control was being exerted on the electrons within it. This was shown by the various colors displayed when they were exposed to UV light.

Brus was aware that he had stumbled on something new and focussed on experimenting and theorizing about the phenomenon. His discovery was the start of what became an exponential growth in a new area of science, to which Brus continued to make valuable contributions.

Commentary on the Chemistry Laureates by John Emsley, Chemistry correspondent, ScienceWatch.