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Ion-exchangeable titanium-oxide nanotubes have commanded considerable interest from the materials science community in the past five years. Synthesized under hydrothermal conditions from TiO2, typical nanotubes are 150–200 nm long and 8–20 nm wide. High resolution TEM images revealed that unlike multiwall carbon nanotubes which are made of coaxial single-wall nanotubes, the titania tubes possess a spiral cross-section. An interesting feature of the titania tubes is their considerable ion-exchange capacity which could be utilized e.g. for enhancing their photocatalytic activity by doping the titania tubes with CdS nanoparticles. In this contribution we present a comprehensive TEM, FT-Raman and FT-farIR characterization study of the formation process. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Networks built from carbon nanostructures and in particular from nanotubes promise exciting nanoelectronic applications. It is thus important to fully understand the quantum mechanical rules of charge propagation through these nanostructures. Some features of the electronic properties of the nanosystems are of purely geometrical origin. These can be investigated in the framework of the jellium model. Wave packet dynamical calculations showed that, when the current is tunneling in a transversal direction through a carbon nanotube “sandwiched” between two electrodes, the energy dependence of tunneling probability shows a plateau in a well defined range. In this work, by solving analytically the stationary Schrödinger equation of a model system, we demonstrate that this plateau is due to electrons being trapped in stationary states of the nanotube. Geometrical features, like diameter dependence of the wave functions and binding energies are studied. Comparison of the results of the widely used zone folding technique with exact jellium wave functions shows a discrepancy at small diameters and an excellent agreement for d > 1 nm. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

Due to their geometry and asymmetric transport properties, carbon nanotube Y-junctions make it possible to create three-terminal nanoelectronic devices and fully nanoscale device networks. To understand the propagation of electron waves in these nanoscopic "wave guides", we have simulated the STM images of such systems by calculating the transversal propagation of electronic wave packets through an STM model. The STM tip acts as a local injection source, the variation of the probability density along the branches of the Y-junction gives information about the wave packet reflections and localized states. [ABSTRACT FROM AUTHOR]