NER: Nanostructures from Magnetic Centers and Liquid Crystal Linkers

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This project seeks to synthesize nanoscale structures based on inorganic and organic components likely to combine to give interesting magnetic properties, and to identify assembly methods that confer nanostructural control. The inorganic centers, nanoparticles of magnetic semiconductors, will be explored for unusual magnetic properties, size dependent magnetic ordering and quantum control. Lyotropic liquid crystals will be tested as organic linkers for their utility in fabricating nanoscale frameworks. Adapting procedures developed for nanoparticles of semiconductors such as CdS or CdSe, europium chalcogenide EuQ (Q = O, S, Se, Te) nanoparticles will be synthesized. The europium chalcogenides are of interest because they exhibit magnetic properties strongly dependent on the electronic band gap. Given what is known about the effect of particle size on the band gap of semiconductors, size selection of these nanoparticles should determine the magnetic properties. The organic linkers, self-assembled momnolayers ( SAMs), polyanions and lyotropic liquid crystals, are chosen for their ability to self organize, and provide sites of attachment for inorganic clusters. In particular, the lyotropic liquid crystals form a variety of structures, lamellar films, hexagonally packed microtubules and micelles which can be locked into place using polymerizable monomers . The test case cluster is the manganese oxo cluster, known as Mn-12 ([Mn12O12HAc162HAc2H2O] where Ac = acetate). This cluster has a core of metal-oxygen atoms surrounded by a coating of acetate groups. By ligand exchanging acetate groups from the cluster with carboxylates bound to a surface, the Mn-12 can be patterned onto substrates. The advantage of the lyotropic liquid crystals is they contain a surface of carboxylic acids, where Mn-12 may be attached. %%%The study of magnetic semiconductor nanoparticles represents an original and fundamentally new direction. In addition to expanding the knowledge of molecular magnetic materials, the study of these nanoparticles will provide a unique example of how magnetic phenomena evolves from molecules to bulk solid materials. The use of novel organic linkers using lyotropic liquid crystals, may provide an ideal framework for organizing magnetic clusters. Method for organizing material on the nanometer length scale is crucial to the development of nanoscale science that will directly impact technologically "hot" areas such as magnetic information. Students trained in the areas of synthesis, characterization, and applications of nanoscience and engineering, which are prioroity areas of high interest to industry, are very competitive in the industrial and academic job market. This project is co-funded by the Chemistry Division and the Division of Materials Research.***