Arrays of nanoparticles can, on command, turn a window into a mirror and vice versa

A team of researchers at Imperial College London, led by Professors Joshua Edel and Alexei Kornyshev, have developed a filter on which the distance between nanoparticles can be controlled. Thanks to this, its surface can become mirrored or transparent, like ordinary glass.

To do this, scientists have created conditions under which gold nanoparticles are localized at the interface between two immiscible liquids. Applying a small voltage, they demonstrated the features of the layer of nanoparticles, which, changing their density, made the surface mirror-like or transparent.

The distance between the nanoparticles determines whether the layer will transmit or reflect light waves of different lengths. In one mode, all waves are reflected, and the layer acts like a mirror, while in the other, where nanoparticles are dispersed, all waves pass through the filter unhindered, like through a normal window.

Unlike previous nanoscopic systems, where the optical properties of the material are irreversibly changed by chemical action, the electrical systems from London are reversible.