Fraunhofer Institute for Reliability and Microintegration IZM, Gustav-Meyer-Allee 25, D-13355 Berlin, Germany
Metal atomic clusters are attractive in many industrial applications for their catalytic activity. Palladium clusters are commonly used in microelectronic surface modification techniques for electroless metal layer deposition (Printed circuit board fabrication) but are applied in chemical catalysis as well. As the size of metal clusters correlates with their specific catalytic activity, size selective cluster generation is highly desirable. Different attempts are suitable. According to our new method, metal ions are reduced in aqueous liposome dispersions. The precipitation of solid metal, typical for stabilizer free systems, there does not occur. Instead, the growth process of metal clusters is delayed and thus clusters of intermediate size (and activity) can be isolated.
The only candidates for stabilizing action present are the lipid head groups at the liquid/liquid interface of liposome membrane and aqueous solution. The lipid membrane, regarded as a two dimensional liquid, substantially influences diffusion controlled cluster growth and therefore can be used to generate clusters of desired size and catalytic activity. First results will be presented and further research intentions will be stated.