(275b) Metal Chalcogenide Nanotubes [Invited]

Research on nanostructure materials has grown exponentially during the last decade due to their interesting properties exhibited by quantum confinement of electrons. In particular, the ability of layered materials to curl up into nested fullerenes or nanotubes have attracted the attention of many scientists. A number of techniques for the synthesis of fullerene-type (F) MQ2 (M = Ti, Nb, Za, Mo, W, Re; Q = S, Se) as well as MQ2 metal chalcogenide nanotubes (NT) have been described. Each of these methods is different from the others and produces products of different characteristics, and - depending on the reaction conditions - microtubes (MT) or onion shell structures (OS) can be obtained as well. This fact indicates that fullerenes and nanotubes represent a genuine part of the phase diagram of many layer-type systems. The most succesful synthetic strategy for the chalcogenide fullerenes and nanotubes starts the oxide nanoparticles which can be converted to the corresponding sulfides in a subsequent by sulfidization step. We present new pathways for the synthesis of metal chalcogenide nanoparticles in bulk quantities, which have been prepared with different morphologies and properties. The preparation methods used vary from solvo- and hydrothermal and thermal decomposition, over a coating technique and H2S-reduction to MOCVD (metal organic chemical vapour deposition). The nanomaterials exhibit tubular, onion- and sheet-like structure respectively in the nanorange as shown by high resolution HRTEM studies. The samples were further characterised by XRD, small area electron diffraction (SAED), EDX, and EELS. Furthermore, the oxide precursors of the chalcogenide nanotubes have a versatile surface chemistry, which has been utilized for functionalization with organic chromophores, polymers and biological markers. Besides the surface functionalization, metal oxides nanoparticles and nanotubes have been doped with alkali and 3d transition metals resulting in metallic or magnetic nanotubes with ferromagnetic ordering at room temperature. Layered transition metal chalcogenides have potential applications as cathode materials for rechargeable high-energy density lithium batteries, as catalysts for hydrosulfurisation or as lubricants. Reversible electrochemical metal intercalation has been achieved for several representatives.