Gold and silver alloy particles have been made using a simple technique involving ionic liquids.

The team, led by Tsukasa Torimoto at Nagoya University and Susumu Kuwabata at Osaka University in Japan, have used a process called sputter deposition to form bimetallic particles. The particles, which have applications in biosensors and as catalysts, are formed in an ionic liquid from atoms sputtered from a metal foil.

Torimoto explained that the team investigated ionic liquids because of their very low vapour pressures. This means they can be used under the high vacuum conditions required for sputter deposition used here, without their physical and chemical properties changing.

The technique involves bombarding a gold and silver metal foil with high energy gaseous ions. Metal atoms are ejected from the surface of the foil into an ionic liquid, where they coalesce to form the bimetallic nanoparticles.

Up to now, explained Torimoto, it has been difficult to obtain homogeneous alloy nanoparticles using conventional solution methods because of the differing chemical redox potentials of the metals. Using the sputtering technique the composition of the particles and their properties can be tuned by varying the composition ratios of the metal foil.

Frank Endres at Clausthal University of Technology in Germany said the team 'present a simple and therefore elegant process for the large-scale production of metal and alloy nanoparticles'. He suggested a further step could be to combine the sputter technique used by Torimoto with a plasmaelectrochemical deposition method developed by himself and colleagues in Germany. 'This might be a route to making ternary compound nanoparticles,' he explained.

Katherine Davies