Semiconductors block metal compounds

By covalent linkage of different types of molecules it is possible to obtain materials with novel properties that are different from those of the parent compounds. Examples of such materials are block-copolymers, soaps, or lipids which can self-assemble into periodic geometries with long-range order. Due to their amphiphilic character, these molecules tend to micellize and to phase-separate on the nanometer scale. By this self-assembly process the fabrication of new na-noscopic devices is possible, such as the micellization of diblock-co-polymers for the organization of nanometer-sized particles of metals or semiconductors [72 - 74]. The micelle formation is a dynamic process, which depends on a number of factors like solvent, temperature, and concentration. Synthesis of micelles which are independent of all of these factors via appropriately functionalized dendrimers which form unimolecular micelles is a straightforward strategy. In... 

The molybdenum neopentyUdene complex Mo(CHBu )(NR)(OBu )2 is the active catalyst used in a fascinating development for the synthesis of 11-Vt semiconductor clusters (ZnS, CdS, PbS) and silver and gold nanoclusters of predictable size within microdomains in films of block copolymers prepared by ROMP. Block copolymers of norbomene and a functionalized norbomene that wiU complex with a metal-containing compound were prepared and characterized as monodisperse materials. The functionalized component (amine, alkoxide, or thiolate) then sequestered the metal and the metallated block copolymer was cast into a film which was subsequently treated with H2S to convert the metal into the sulfide. The molybdenum complexes have also featured in the development of the synthesis of side-chain liquid crystal polymers by living ROMP.98 99... 

The important step involves the solubilization of inorganic compounds into the micellar core. As a guideline for optimum precursor materials and micellar core blocks, one can use Pearsons hard / soft acid /base (HSAB) concept [151], which has been generalized to include metals and semiconductors [152]. The general strategy is to start from weakly coordinated metals, e.g. Pd(OAc)2 or Pd(C104)2 which are complexes of a soft acid (the transition metal ions) and a hard base (acetates, perchlorates, etc.). The formation of more stable complex of a soft acid with a softer base, e.g. polyvinylpyridine, to assemble the micellar core, is the driving force for solubilization. The polymer complex should not be too stable since over-stabilization could prevent the formation of the desired colloid in the subsequent chemical reaction. 

---