British physicists created the first turning off the «liquid mirror»

© Illustration RIA Novosti . Alina Polyanina So the artist presented his work mirror of nanoparticlesBritish physicists created the first turning off the «liquid mirror»© Illustration RIA Novosti . Alina Polyanina

Scientists from the UK has created an unusual nanoparticles that can simultaneously be transparent to the light and turn into a perfect mirror, and published the «recipe» for their production of the article in the journal Nature Materials.

«Nanoparticles are in a very delicate balance. We spent a long time trying to get them to behave properly, but they are constantly glued to each other, and not evenly distributed in the solution. We had to create dozens of models and spend an equally large number of experiments in order to create a truly managed layer of nanoparticles,» says Joshua Edel (Edel Joshua) from Imperial College London (UK).

Nanoparticles and thin strips of some metals, for example gold or silver, capable of absorbing visible light and pass it on to other forms of electromagnetic radiation. At this time, the surface of metal there are the so-called plasmons — collective oscillations of electrons that can absorb and emit energy in the form of light waves.

One of the most striking examples of plasmons is considered to be the Roman Lycurgus Cup — a vessel made of glass that change transparency depending on the lighting. Other examples of their work — microwave «invisibility cloak», created in 2014, and a futuristic transparent display on plasmons created at MIT.

Edel and his colleagues, including Russian physicist Alexei Kornyshev, very long time tried to eliminate one of the main disadvantages of plasmons — an almost complete inability to manage their properties after they were made.

As the scientists explain, then, as the plasmons interact with light and what light they absorb or pass through him, depends on two characteristics — size and distance between the individual nanoparticles. Physics long enough have learned to control the position of individual nanoparticles, but «conducting» the millions and billions of plasmons remains a challenge.

The Kornyshev, Edel and their supporters were able to solve this problem using two ingenious ideas: they placed the nanoparticles is not on the surface of another metal or silicon, as is usually done by scientists in experiments with surface plasmons, in the aqueous solution, and created a very special chemical environment, allowing you to control the position of all particles in solution using pulses of electricity.

The creation of this «liquid mirror» began with the fact that scientists noticed that the average gold nanoparticles coated with a polymer film, can repel each other or to approach each other, not sleepas if their charge and placed in a special electrolyte consisting of two immiscible liquids with different electrical properties.

At rest, this liquid causes the gold flakes to be removed from each other at a sufficiently large distance, with the result that it becomes transparent to visible wavelengths. If you skip through it an electric current, the position of ions in the electrolyte will change, and part of charged particles are carried with the particles of gold and will build into a kind of flat sheet.

Metal particles in it will be close enough in order to enable them to absorb photons of visible light and re-emit them in the opposite direction, which will make the surface of the solution mirror. If they are not glued to each other that allows to make a mirror transparent by turning off the current or changing the order of the pole at its source.

Such structures, as physicists say, allow not only to create electric mirrors, and many other ekzoticheskih optical devices with controllable optics, which today are considered fantasy. Such plasmonic devices, according to Edel and Kornysheva, can significantly accelerate the speed of the global network, to create new telescopes and provide the basis for light computers of the future.


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