Could you explain the significance of your article to the non-specialist?

Most industrial metal catalysts contain very costly metals and must therefore have as large a surface-to-volume ratio as possible. This is the solution provided by nanoparticles. Our research is concerned with the parameters governing interactions between metallic nanoparticles and a reactive surrounding material, and hence with the catalytic properties of such nanoparticles. Chemical reactivity of the metallic active phase can be significantly modified by using materials in the form of nanoparticles. Such modifications are associated with non-standard structure and specific electronic properties. These kinds of effects are usually grouped together under the heading of size effects in catalysis. To implement such nanoparticles, one requires a powdered support with high surface area which can induce electronic and structural effects on the supported nanoparticles : the so-called "support effects". Catalytic properties are also modified by alloying effects when a second metallic partner is introduced due to modifications induced by chemical binding between the two partners. These effects of size, support and alloying on chemical activity can be accurately studied if one is able to deposit on any support nanoparticles with well defined size and composition. This can be achieved with the use of the low energy cluster beam deposition technique (laser vaporisation).

What has motivated you to conduct this work?

One of the aims of surface science studies on extended surfaces is to understand and rationalize some aspects of heterogeneous catalysis. A major drawback of this approach is that the influence of the finite size of nanoparticles and support effects influence on chemical activity cannot be investigated. The use of an efficient method such as the laser vaporisation to synthesise well defined mono or multi-metallic supported nanoparticles should allow to bridge the gap between real world catalysis and the very fundamental surface science approach.

Are there any particular challenges facing future research in this area?

The motivation for creating well-defined nanoparticles comes from several different areas of science and technology such as optics or magnetism. Here we would like to mention possible applications in the area of fundamental studies in catalysis. Most commercial catalysts are small metal clusters supported on oxides and in many reactions the rate depends on the size and structure of the metal cluster. Since significant geometrical and electronic changes occur for cluster sizes ranging from 1 to 10 nm, reaction rates often change as well. Nevertheless, there is only limited fundamental knowledge about the relationship between the structure and the composition of these nanoparticles and their catalytic behaviour. Increasing this knowledge by producing and studying perfectly tailored supported nanoparticles should allow to develop new efficient industrial catalysts.