Bottom-up synthesis and top-down organisation of semiconductor and metal clusters on surfaces

Near-spherical dendrimers can be used as templates for bottom-up syntheses of semiconductor clusters. Starting from methanolic solutions of Cd2+, sulfide, and poly(amidoamine) dendrimers, CdS clusters precipitate at the dendrimers. A preparation inside the dendrimers is only possible when the protonation of the latter is carefully controlled. The clusters have diameters above about 2 nm and show blue photoluminescence. The patterning and orientation of CdS/dendrimer clusters on flat surfaces are attained by microcontact printing. Depending on the ripening of the CdS/dendrimer suspension, a sub-micrometer stripe pattern develops inside the micrometer-scaled patterns; it extends over the complete surface. Rod-like plant virions with a different type of lateral organisation can be oriented on a flat substrate by applying mechanical forces during immobilisation from suspensions. These virions can also be employed as templates, in this case for creating metal structures by electroless deposition (chemical metal deposition). The structures are wire-like with diameters of 3-4 mu and are confined inside the central channel of the virions. The early stage of the metallisation process is analysed, and a model that accounts for the selectivity is presented. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.