A new way to prepare nanostructured materials: Flame spraying of microemulsions

In this report we describe a new method to obtain nanostructured coatings or powders based on the flame decomposition of microcompartmentalized solutions. Metal nanoclusters of well-defined size are obtained by reduction of a metal salt inside the water compartment of water in oil (w/o) microemulsions, formed by water in hexane and stabilized by an appropriate surfactant. Metal nanoclusters can be separated from the mother solution by spraying the microemulsion solution into an air/acetylene flame. In this way, nanostructured coating or powder, almost preserving the original structure of the nanoparticles synthesized in the microemulsion system, can be obtained in quantities sufficient for industrial applications. As an example we report the flame spraying of gold microemulsions to produce gold coating onto silicon wafers. To the best of our knowledge, this study reports a new method allowing the use of a microemulsion synthetic pathway for the production of consistent amount of nanoparticles. This method could be of great utility in many applications involving nanoparticles in the fields of physics, chemistry, biotechnology, and biology.