Two thousand years ago, Roman glass blowers used gold nanocrystals to create vases with brilliant colours ranging from red to purple. Today, gold nanocrystals are being used as catalysts in chemical reactions and may even become high-density data storage devices.

Gold nanocrystals aren’t gold in colour. They change colour as their size and shape change.

A team led by Prof. Paul Mulvaney, at the University of Melbourne, is using gold nanocrystals as a colour-coded catalyst.

These catalysts work by speeding up the transfer of electrons between molecules, acting as an electron reservoir. The rate of the chemical reaction depends on the size, crystal structure, shape and composition of each catalyst particle.

Since the number of electrons stored in the catalytic gold nanocrystal affects its colour, the scientists were able to use colour change to trace the steps of the reaction.

“The ability to watch a single nanocrystal as it catalyses a chemical reaction is unprecedented. We can now compare different sizes and shapes of nanocrystals,” says Paul. “Eventually, we may be able to study chemical reactions taking place one molecule at a time.”

Extending the idea, postdoctoral researcher Dr Alison Funston is researching using colour change to store high-density data in binary code—the language of computers.

For more information: The University of Melbourne, Paul Mulvaney, Tel: +61 (3) 8344 2420, mulvaney@unimelb.edu.au, www.nanoparticle.com