The video above shows the system in action. The layer first acts as a window onto a £10 note below, and then reflects the £1 coin above when a voltage is applied.
The distance between the nanoparticles determines whether the layer permits or reflects different wavelengths of light. At one extreme, all the wavelengths are reflected, and the layer acts as a mirror. At the other extreme, where the nanoparticles are dispersed, all wavelengths are permitted through the interface and it acts as a window.
It was remarkable how closely the theory matched experimental results.
– Professor Alexei Kornyshev
In contrast to previous nanoscopic systems that used chemical means to change the optical properties, the team’s electrical system is reversible.
Study co-author Professor Alexei Kornyshev, from the Department of Chemistry at Imperial, said: “Finding the correct conditions to achieve reversibility required fine theory; otherwise it would have been like searching for a needle in a haystack. It was remarkable how closely the theory matched experimental results.”
Co-author Professor Anthony Kucernak, also from the Department of Chemistry, commented: “Putting theory into practice can be difficult, as one always has to be aware of material stability limits, so finding the correct electrochemical conditions under which the effect could occur was challenging.”
Professor Kornyshev added: “The whole project was only made possible by the unique knowhow and abilities and enthusiasm of the young team members, including Dr Yunuen Montelongo and Dr Debarata Sikdar, amongst others who all have diverse expertise and backgrounds.”
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‘Electrotuneable Nanoplasmonic Liquid Mirror’ by Yunuen Montelongo, Debabrata Sikdar, Ye Ma, Alastair J. S. McIntosh, Leonora Velleman, Anthony R. Kucernak, Joshua B. Edel, and Alexei A. Kornyshev is published in Nature Materials.