Make mine a decaf study increases knowledge of nanoparticle growth

A team of researchers from Leicester's Department of Physics and Astronomy and France’s G2ELab-CNRS in Grenoble have for the first time observed the growth of free nanoparticles in helium gas in a process similar to the decaffeination of coffee, providing new insights into the structure of nanoparticles.

Nanoparticles have a very large surface area compared with their volume and are often able to react very quickly. This makes them useful as catalysts in chemical reactions and they are often used in sports equipment, clothing and sunscreens.

In a paper published by the Journal of Physical Chemistry Letters the researchers measured how helium ions cluster with neutral helium atoms and grow into nanoparticles.

Dr Klaus von Haeften (pictured) said: “We concluded that the increased pressure forced more and more helium atoms to bind to the ions gradually, until the clusters grew to nanometre-sized particles. This process continued until the nanoparticles reached the maximum size possible which also depended on the temperature. Further increase of the pressure was found to reduce the size, which we interpreted as compression. These size changes could then be followed in great detail. For low and moderate pressures the size changed rather rapidly whereas in the high pressure region the changes were slow.”

By analysing how quickly the particle volume changed with pressure the researchers were able to investigate the structure of the nanoparticles.

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