The two alternative configurations of the gold nanoclusters containing 561 atoms. Image: Swansea University.
The two alternative configurations of the gold nanoclusters containing 561 atoms. Image: Swansea University.

A nanomaterials expert at Swansea University in the UK has been looking at how gold nanoparticles survive when subjected to very high temperatures. This research has potential applications in industrial sectors such as catalysis and aerospace, where particles of nanometer dimensions are subjected to similarly high temperatures.

The results of the study, a three-way collaboration between the universities of Birmingham and Swansea in the UK and Genoa University in Italy, are reported in a paper in Nature Communications. The study showed that gold nanoparticles of a precisely selected size (561 atoms ±14) are remarkably robust against diffusion and aggregation, but their internal atomic arrangements do change when exposed to very high temperatures.

The researchers used an ultrastable, variable-temperature stage in an aberration-corrected scanning transmission electron microscope to subject an array of size-selected gold nanoparticles (or clusters) to temperatures as high as 500°C while imaging them with atomic resolution. The particles were deposited from a nanoparticle source onto thin films of silicon nitride or carbon.

The experiments showed that binding of the gold nanoparticles to point defects on the surface of the films proved sufficiently strong to fix them in place, even at the top of the temperature range. But the atomic structures of the clusters fluctuated under the heat treatment, switching back and forth between two main atomic configurations (‘isomers’). These configurations were a face-centred cubic structure, similar to a small piece of bulk gold, and a decahedral arrangement with a symmetry forbidden in an extended crystal. The researchers were even able to measure the tiny difference in energy (only 40meV) between these two different atomic architectures.

"These advanced experiments have allowed us to make a new measurement for nanoparticles deposited on a surface – the difference in energy between two competing atomic arrangements," said Richard Palmer, head of the Nanomaterials Lab in Swansea University's College of Engineering. "It's something that the people who use computers to calculate the properties of nanomaterials are particularly excited about, a kind of reference point if you like. And the images show that our little nanoparticles are really rather tough creatures, which bodes rather well for their applications in future industrial manufacturing."

The Swansea Lab's research is focused on scaling-up the production of such nanoparticles by 10 million times, to the level of grams and beyond. "We need very small things in very large numbers to realise the true potential of nanotechnology," said Palmer.

This story is adapted from material from Swansea University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.