Nobel Prize for Chemistry: quantum dots discovery

Guiding you through this year's Nobel Prize for Chemistry, James Tytko:

When it comes to chemistry, size certainly matters, and now one of the world's largest awards for the subject rewards some of the tiniest of entities we can make.

Known as quantum dots, these atomic-scale structures, a millionth of a millimetre across and composed of just a few thousand atoms, are tiny inorganic particles that glow a range of colours from red to blue when exposed to light. The colour they emit depends upon the size of the particle.

They are what make modern LED television screens and monitors possible; they also boost the efficiency of the photovoltaic cells we use to capture the Sun's energy, make highly-sensitive light detectors feasible, work as catalysts to speed up industrially important reactions such as hydrogen production, and work as diagnostic sensor molecules for medical imaging and disease.

All of this hinges on the fact that as particles become smaller, quantum effects kick in that alter their chemistry.

One of the winners, of this year's Nobel Prize, Russia's Alexey Ekimov, made the crucial observation in the early 1980s that stained glass changed colour according to how long and how hard it was heated. He correctly reasoned that tiny particles of copper in the glass were growing or shrinking with the temperature, and this was affecting the way they interacted with light.

Later, working in the US, Louis Brus made a similar observation that light-driven reactions involving solutions of the substance cadmium sulphide changed over time; he realised that the crystals were growing in the solution on his lab bench, and as their size changed, so did their quantum properties.

It was obvious that if the size and structure of the particles could be precisely controlled, there was huge potential to manipulate their chemical properties.

That breakthrough came in the early 1990s, when the third recipient, Moungi Bawendi, pioneered a way to make quantum dots with uniform sizes and prescribed sizes, opening to door to the technological, industrial and medical exploitation of the science that we see today.

So although the discovery hinges on the science of the very small, the implications and applications are huge and have been world-changing; moreover, it proves that size really does matter.