Nanowires

Tight-binding electronic structure calculations for periodic systems are often carried out in non-primitive unit cells, or for imperfect (eg random-alloy) nanostructures, such as nanowires. In the first case bands exist but they are difficult to identify due to the choice of unit cell for the calculation, while in the second case bands only exist in an approximate sense. The Brillouin zone unfolding technique applied to tight-binding calculations provides a powerful tool for extracting the true primitive-cell bands from non-primitive cells. Also, it ...

Self-assembled micro/nanowires of melamine and seveal aromatic acids, including thiocyanuric acid, trimesic acid, terephthalic acid, and 5-sulfoisophthalic acid, are formed through evaporation of water in a solution mixture of acids and melamine. These self assemblies show crystalline structures. Except for microwires of 5-sulfoisophthalic acid and melamine, other microwires are semiconductors. They may be used for sensors, catalyst, optoelectronics, etc. Keywords: Nanowires; Microwires; Self-Assembly; Aromatic Acid; Melamine.

Engineering materials at the nanoscale by combining controlled nanomaterial synthesis and directed assembly methods offers the potential to create new electronic and optical devices with improved performance and functionality. Semiconductor nanowires have been of particular interest as a model system for studying new physical phenomena arising from their scaled geometries as well as for applications in high performance vertical transistors,

We investigate the role of dipolar interactions on the magnetic properties of nanowires aggregates. Micromagnetic simulations show that dipolar interactions between wires are not detrimental to the high coercivity properties of magnetic nanowires composites even in very dense aggregates. This is confirmed by experimental magnetization measurements and Henkel plots which show that the dipolar interactions are small. Indeed, we show

Single-crystals of MnFe2O4 nanorods with an average diameter of 20 nm and length of 250 nm were synthesized by a hydrothermal process at 180 °C after 12 h. High-resolution transmission electron microscopy (HRTEM) and electron diffraction (ED) analysis revealed that the nanorods grow along the [110] axis, which is one of the easy magnetization axes of the material MnFe2O4. It was found that the nanorods exhibited a saturation magnetization (Ms) of 68.02 emu/g, which is much higher than that of quasi-spherical particles of MnFe2O4, prepared by other approaches such as solid-state reaction methods (Ms = 36.7 emu/g), and coprecipitation processes followed by annealing in vacuo at 400 °C (Ms = 24.4 emu/g). The oriented growth along the easy magnetization axis of MnFe2O4 was suggested to be responsible for the improvement of magnetic properties of MnFe2O4 nanorods. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)