Coaxial Nanocables Research Articles

Silver Nanowires Can Be Directly Coated with Amorphous Silica To Generate Well-Controlled Coaxial Nanocables of Silver/Silica

This paper describes a simple and convenient approach that allowed for the facial synthesis of silver/silica coaxial nanocables with well-controlled sheath thicknesses in the range of 2−100 nm. The lengths of these nanocables could be up to ∼50 μm. Such nanocables were prepared by directly coating bicrystalline silver nanowires with conformal sheaths of silica through a sol−gel process. The silver nanowires were, in turn, synthesized using a polyol method that involved the reduction of silver nitrate with ethylene glycol in the presence of poly(vinyl pyrrolidone). The thickness of silica coating could be controlled by changing the concentration of the precursor solution and/or the reaction time. Selective removal of the silver cores led to the formation of silica nanotubes having well-controlled dimensions and wall structures.

Coaxial nanocables: Fe nanowires encapsulated in BN nanotubes with intermediate C layers

Fe-filled BN nanocables with intermediate C layers were fabricated. Complete phase separation between C and BN was distinguished using electron energy loss spectroscopy (EELS) measurements and high-resolution transmission electron microscopy (HRTEM) images by the characteristics of well-ordered BN layers and turbostratic C ones. A two-step growth model is proposed for the formation of this remarkable structure. The idea of introducing intermediate C layer, overcoming the wetting restriction of BN surface, may be employed for fabrication of BN nanocables filled with other metal cores.

Fabrication of a novel polypyrrole/poly(methyl methacrylate) coaxial nanocable using mesoporous silica as a nanoreactor

We report on the fabrication of a polypyrrole/poly(methyl methacrylate) coaxial nanocable through the sequential polymerization of methyl methacrylate and pyrrole monomers inside the channels of mesoporous SBA-15 silica, followed by the removal of the silica template.

Coaxial Three-Layer Nanocables Synthesized by Combining Laser Ablation and Thermal Evaporation

Coaxial three-layer nanocables consisting of a crystalline silicon core, a silicon oxide interlayer, and a carbon outer sheath (see Figure) have been obtained using a combination of laser ablation and thermal evaporation. These novel multilayer nanostructures, which are interesting candidates for nanoelectronic devices, are characterized using a variety of techniques. A growth mechanism is proposed.

Coaxial Three-Layer Nanocables Synthesized by Combining Laser Ablation and Thermal Evaporation

Coaxial Three-Layer Nanocables Synthesized by Combining Laser Ablation and Thermal Evaporation

Synthesis of coaxial nanowires of silicon nitride sheathed with silicon and silicon oxide

Coaxial nanowires, with about 45 nm in diameter and about 15 μm in length, have been synthesized by reaction of silicon dioxide nanoparticles with active carbon at 1450°C in flowing nitrogen atmosphere. Their structures consist of an α-phase silicon nitride core, an amorphous silicon and a silicon dioxide outer shell, similar to those of coaxial nanocables. The formation mechanism of the coaxial nanowires is discussed.

Coiled structure of eccentric coaxial nanocable made of amorphous boron and silicon oxide

Exotic nanocable with coiled structure has been found in soot obtained by a reactive laser ablation as a byproduct of the formerly reported coaxial nanocables [Y. Zhang, K. Suenaga, C. Colliex, and S. Iijima, Science 281, 973 (1998)]. Electron energy-loss spectroscopic imaging has revealed the coaxial structure made of amorphous boron and silicon dioxide with amorphous carbon sheath. We infer that the coiled structure is attributed to a difference in the growth rate between amorphous boron and silicon dioxide that are found to comprise eccentric coaxial nanocable.

Coaxial Nanocable: Silicon Carbide and Silicon Oxide Sheathed with Boron Nitride and Carbon

Multielement nanotubes comprising multiple phases, with diameters of a few tens of nanometers and lengths up to 50 micrometers, were successfully synthesized by means of reactive laser ablation. The experimentally determined structure consists of a beta-phase silicon carbide core, an amorphous silicon oxide intermediate layer, and graphitic outer shells made of boron nitride and carbon layers separated in the radial direction. The structure resembles a coaxial nanocable with a semiconductor-insulator-metal (or semiconductor-insulator-semiconductor) geometry and suggests applications in nanoscale electronic devices that take advantage of this self-organization mechanism for multielement nanotube formation.