Hot nanoparticles produce giant and explosive bubbles

phys.org | 7/12/2018 | Staff
Nighty (Posted by) Level 3
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When gold nano particles in water are illuminated by a laser, they get very hot: well above the boiling point of water. The formation of vapour bubbles caused by this, is well-known. New experiments, however, using a very high speed camera, now show that before this, a bubble is formed that is much larger and, subsequently, explodes violently. For energy conversion of the particles to the liquid they are in, this discovery of early phase dynamics is very important. Researchers of the University of Twente and the University of Utrecht in The Netherlands now publish these new results in the Proceedings of the National Academy of Sciences (PNAS).

Nanoparticles locally speed up the boiling of water when laser light illuminates them. At the surface of the particles, electrons collectively oscillate. Vaporization via these so-called 'plasmons' is much stronger than in case you would just locally heat the water using a laser. Until now, the 'early youth' of this bubble formation was not taken into account, while this first phase of nucleation and early dynamics determines the subsequent phases to a high extent.

Behavior - Time - Scales - Milliseconds - Thanks

Until now, the bubble behavior was studied at time scales of milliseconds. Thanks to the very fast camera "Brandaris128," developed by the University of Twente, it is now possible to look even at the nanosecond timescale. A little while after the nanoparticle heats up, a bubble is formed that is a hundred times bigger in volume than the later bubbles. This bubble explodes, followed by smaller bubbles oscillating. In...
(Excerpt) Read more at: phys.org
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