UTS-led team makes nanoparticle breakthrough for gold Tuesday, 29 March 2016

Gold is known as a noble metal — it does not readily react with most other substances, and thus will not rust, corrode, or tarnish. Now researchers investigating the growth of nanoparticles have found the mechanism behind this, and how they can customise the properties of gold nanoparticles.

The team from the University of Technology Sydney (UTS) School of Mathematical and Physical Sciences, led by Professor Jeffrey Reimers and Association Professor Mike Ford, worked with collaborators from the Technical University of Denmark and the University of Sydney. They found a way to explain the chemical bonding process that occurs during the growth of gold nanoparticles.

This discovery has implications for the application of nanotechnology in biomedical imaging, drug delivery, and electronics.

“What makes gold special – and, for that matter, what makes sulphur special – turned out to be the key in understanding how nanoparticles grow,” explained Professor Reimers.

“The electrons in gold travel so fast they become heavy, an effect more important for gold than other atoms … so gold has the appearance of a metal, but with a strange colour and many more properties like those of non-metals such as sulphur.”

For years, scientists had postulated that sulphur glue sticks to and thus protects gold metal surfaces and nanoparticles due to the fact that the elements can react together to form strong covalent bonds, where electron pairs are shared between atoms, in compounds known as Au(I)-thiolates.

The new research from the UTS finds the bonding mechanism which binds sulphur to gold is in fact due to the van der Walls force — a type of attraction between molecules of quantum mechanical origin.

By identifying the significance of the “glue” that binds the surface of the gold nanoparticles to keep potentially destructive chemicals out of range, the team have found the key that is critical to customising the properties of nanoparticles.

With this breakthrough, other researchers and engineers can now design experiments that really tell how nanoparticles grow, and invent new generations of gold nanotechnologies.

Nanoparticle developments, especially in controlling the size and shapes of nanoparticles, and making them behave in certain ways, will be key for the next generation of non-invasive and targeted treatments for diseases such as cancer.