Laser Deposition Method Lays Down Ionic Liquids

Ionic liquids can be deposited on solid surfaces as thin films and nanoscale droplets, according to researchers in Japan who developed a molecular-beam-based vacuum deposition method for that purpose (ACS Nano, DOI: 10.1021/nn101036v). Ionic liquids are increasingly being used in chemical synthesis, catalysis, and a variety of energy-related applications. But until now, little has been done to extend the collection of controlled-deposition methods widely used in the semiconductor and device-physics fields to ionic liquids because of their negligible vapor pressure, which presents difficulties in handling these materials with standard vacuum techniques. In the system designed by Shingo Maruyama and Yuji Matsumoto of the Tokyo Institute of Technology and coworkers, light from a continuous-wave infrared laser drives a molecular beam of one or more imidazolium salts to a surface. By adjusting the laser parameters and preparing the surface in various ways, the team controlled the thicknesses of the films (up to 100 nm) and the sizes and compositions of the one- and two-component droplets, which varied from tens to hundreds of nanometers in diameter.