Nano knowledge could improve catalysis

Although melting behaviour is known to change at the nanoscale, the way nanoparticles melt has remained an open question.

Now, in a paper published in Nature Communications, researchers at Swansea University describe an experiment in which they imaged gold nanoparticles, with diameters ranging from two-to-five nanometres, as they were heated.

The researchers imaged the nanoparticles using an aberration corrected scanning transmission electron microscope, according to Prof Richard Palmer, who led the research.

They then carried out large-scale quantum mechanical calculations, to simulate their results.

“We established that the nanoparticle melts from the outside in, so you have a liquid skin, which is floating around a solid core,” said Palmer. “The melting point of the nanoparticles depends very strongly upon their size.”

Understanding how nanoparticles melt, and predicting their behaviour at elevated temperatures, could help in a range of applications, Palmer said.

In catalysis, for example, chemical reactions typically take place at elevated temperatures on small particles, which have a much lower melting point than their bulk metals.