Ionic water or water containing salts conducts electricity, this is common knowledge but pure water, distilled water, on the other hand behave almost as a good insulator. To make pure water metallic or any material metallic for that matter, a very high pressure needs to be applied. Under these conditions atoms or molecules can be squeezed tight, such that they begin to share their outer electrons, which renders the electrons mobility to roam about, thus making them a conductor just like normal metals. Such a phenomena has been theorised by the geophysicists, who think that it occurs at the centres of massive planets such as Neptune or Uranus that host water in such a metallic state, and also that high-pressure metallic hydrogen can even become a superconductor, able to conduct electricity without any resistance.

However, an international collaboration of 15 scientists from eleven research institutions has now used a completely different approach to produce an aqueous solution with metallic properties (while avoiding explosion) for the first time and documented this phase transition at BESSY II. They achieved this feat by forming a very fine crust of water around electron-sharing alkali metals. Although, water maintained its metallic state for only few seconds, they did not require any high pressure like usual to convert a non-metallic material into electrically conductive metals.

Co-author Pavel Jungwirth, a physical chemist at the Czech Academy of Sciences in Prague, says that seeing the water take on a golden shine was a highlight of his career. The team published its findings on 28 July in Nature [“Spectroscopic evidence for a gold-coloured metallic water solution” by Philip E. Mason, H. Christian Schewe, Tillmann Buttersack, Vojtech Kostal, Marco Vitek, Ryan S. McMullen, Hebatallah Ali, Florian Trinter, Chin Lee, Daniel M. Neumark, Stephan Thürmer, Robert Seidel, Bernd Winter, Stephen E. Bradforth and Pavel Jungwirth].

As we all know alkali metals are not big fans of water, when they come in contact with each other explosion is bound to happen, with sodium and other alkali metals catching fire when they touch water. Kudos, to the team to device a way around this event, thus preventing a violent reaction. Instead of putting a piece of alkali metal into water, they placed a tiny bit of water on a drop of alkali metal, a sodium-potassium (Na-K) alloy, which behaves as a liquid at room temperature.

A time lapse of the metallic water forming, first from a droplet of sodium-potassium alloy, then turning gold colored as electrons and metal cations move into the water on the surface HZB/Nature.

At BESSY II, the experiment was conducted in the SOL³PES high vacuum sample chamber at the U49/2 beamline. The sample chamber contains a fine nozzle which dispatches the liquid Na-K alloy droplets, the silver drops grows for about 10 seconds until it separates from the nozzle. As the droplet grows, some water vapour is released into the sample chamber that forms an extremely thin skin on the surface of the droplet made with only a few layers of water molecules. This rapidly causes the electrons as well as the metal cations to dissolve from the alkali alloy into the water. The released electrons in the water behave like free electrons in a conduction band, therefore acting as an electrical conductor. Using optical reflection spectroscopy and synchrotron X-ray photoelectron spectroscopy the group was able to confirm that, the droplet so produced was metallic indeed, as both the plasmon frequency and the conduction band; the metallic phase quantities were accounted for.

“Our study not only shows that metallic water can indeed be produced on Earth, but also characterizes the spectroscopic properties associated with its beautiful golden metallic luster,” says Seidel.

“You can see the phase transition to metallic water with the naked eye! The silvery sodium-potassium droplet covers itself with a golden glow, which is very impressive,” reports Dr. Robert Seidel, who supervised the experiments at BESSY II. The thin layer of gold-colored metallic water remains visible for a few seconds. This enabled the team led by Prof. Pavel Jungwirth, Czech Academy of Sciences, Prague, to prove with spectroscopic analyses at BESSY II and at the IOCB in Prague that it is indeed water in a metallic state.

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