Ionic liquids shoot for the moon

A smooth, shiny liquid that resists perturbation of its surface is just the thing astronomers are looking for to use in a NASA-proposed infrared Lunar Liquid Mirror Telescope. Such a telescope with an aperture up to 100 meters in diameter located on the moon would be capable of observing objects in space that are 100 to 1,000 times fainter than those visible to the proposed next generation of space-based telescopes that use glass mirrors. An international team led by Ermanno F. Borra of Laval University, Quebec, now has shown that a metal film deposited on the surface of an ionic liquid could be the ideal shiny material (Nature 2007, 447, 979). To serve as a liquid mirror, the material must have low vapor pressure under vacuum, low melting temperature, and high viscosity, and it must remain stable indefinitely-a good description of ionic liquid properties. As a proof of concept, the team used 1-ethyl-3-methylimidazolium ethylsulfate, a commercially available ionic liquid, to test mirror designs in lab dishes. The most promising candidate is a pool of the ionic liquid coated with a nanolayer of chromium and then a nanolayer of silver.