Nanostructure templating in inorganic solids with organic lyotropic liquidcrystals

Various nanoscale semiconducting superlattices have been generated by direc t templating in a lyotropic organic liquid crystal. These include superlatt ices of CdS, CdSe, and ZnS, templated in a liquid crystal formed by oligoet hylene oxide oleyl ether amphiphiles and water. The semiconductor growth pr ocess copied the symmetry and characteristic dimensions of the original mes ophase by avoiding growth of mineral within regularly spaced hydrophobic re gions. The final product was a superlattice structure in which a mineral co ntinuum was featured with hexagonally arranged cylindrical pores 2-3 nm in diameter and 5 nm apart. Most importantly, the superlattice morphology of t he nanostructured systems in contact with the mesophase was found to be the rmodynamically stable with respect to the solid lacking nanoscale features. We also found that both the morphology of features in the nanostructured s olids and their dimension can be controlled through the amphiphile's molecu lar structure and water content in the liquid crystal. The semiconducting s olids CdS, CdSe, and ZnS were all directly templated, while Ag2S, CuS, HgS, and PbS were produced only as nonfeatured solids using identical synthetic methodologies. We propose that interactions of polar segments in template molecules with the precipitated mineral and with its precursor ions are nec essary conditions for direct templating. This is based on the absence of te mplating in the more covalent minerals and also in the presence of salts kn own to bind precursor ions.