on the occasion of his 75th birthday
The chemical construction of organized inorganic matter by using inorganic nanoparticles as building blocks offers a new and promising approach to functional materials with complex architectures and properties. [1] The multiscale ordering, interlinking, and interfacing of preformed nanoparticles may be directed by using artificially structured synthetic templates or through a programmed assembly based on selfencoding elements such as streptavidin-biotin [2] and antibody-antigen complexes, [3] complementary DNA strands, [4] or electrostatic self-assembly. [5] Alternatively, artificial structuring can be achieved by using (meso)porous templates such as silica, synthetic opals, [6] foams, [7] emulsions, [8] or polymers. [9] The exploitation of these strategies remains a significant challenge as the properties and functions of materials are controlled not only by the nature of their building blocks, that is, atoms, molecules, and nanoparticles, but also through their organization into complex assemblies on various length scales.
Recently there has been much interest in the fabrication of ordered two-and three-dimensional devices by using nanotubes/wires as building blocks. [10] Nanotubes/wires with various electronic and mechanical properties can be synthesized by a variety of methods, depending on the nature of the constituent material. Nanotube/wire-nanoparticle hybrid materials, in which nanoparticles are attached to the walls of nanotubes/wires, may combine the unique structural and electronic properties of nanotubes/wires and the outstanding properties of nanoparticles which can tune their electronic structures through their size and morphology. In the past, most efforts towards such hybrid materials focused on carbon nanotubes, with prototype guest particles being Au [11] or Pt [11a,c] as well as semiconductors such as CdSe. [12] This observation is surprising, as carbon nanotubes are very inert and therefore difficult to functionalize. Nanotubes/wires from compounds other than carbon (e.g. TiO 2 , [13] V 2 O 5 , [14] or WS