Cost-saving synthesis of vanadium oxide nanotubes

The synthesis of vanadium oxide nanotubes has been achieved by using V₂O₅ as vanadium oxide precursor. Due to its low cost, high yield and ease of handling, the synthesis starting from V₂O₅ provides an advantageous access to large quantity of the tubular vanadium oxide nanotubes.     

Laser-induced sign reversal of the nonlinear refractive index of Ag nanoclusters in soda-lime glass

Received: 16 February 1998     

Catalytic synthesis and photoluminescence of needle-shaped 3C-SiC nanowires

Needle-shaped 3C-SiC nanowires were grown from commercially available SiC powders in a thermal evaporation process with iron as catalyst. A strong broad photoluminescence peak located around 450 nm was observed at room temperature, which may be ascribed to quantum size effects of nanomaterials. Needle-shaped 3C-SiC nanowires may have great potential applications such as blue-green light-emitting diodes and display devices.     

Effect of deposition parameters on morphology and size of FeCo nanoparticles synthesized by pulsed laser ablation deposition

The experimental parameters that control the surface morphology and size of iron cobalt nanoparticles synthesized at room temperature by pulsed laser ablation deposition (PLAD) technique have been systematically investigated. The nanoparticle synthesis has been achieved at higher operating gas pressures of argon. It was found that nanoparticles upon deposition formed small clusters, the size of which increases with decreasing pressure, increasing laser-energy density, and decreasing target-to-substrate distance. This trend could be attributed to change in the kinetic energy of deposited nanoparticles with varying argon pressure, laser-energy, and target-to-substrate distance. The nanoparticles size and size distribution showed strong dependence on argon pressure and weak dependence on laser-energy density and target-to-substrate distance.     

Relaxed GexSi1−x layer formation with reduced dislocation density grown by ultrahigh vacuum chemical vapor deposition

A mixture of as-grown single-wall carbon nanotubes (SWNTs) and a monochlorobenzene (MCB) solution of polymethylmethacrylate (PMMA) was sonicated and homogenized. As a result, SWNTs were separated from carbonaceous impurities and metal particles, which enabled us to purify the SWNTs by filtration. We also found that the number of short (about 1-μm) SWNTs and thin bundles of SWNTs increased. The thin bundles contained one to three SWNTs. These short, thin SWNTs suspended in the MCB solution of PMMA were spin-coated onto a Si wafer, and could be dispersed on it. Received: 18 July 2000 / Accepted: 20 July 2000 / Published online: 6 September 2000     

Synthesis of crystalline SrMoO4 nanowires from polyoxometalates

Crystalline SrMoO₄ nanowires were synthesized via a facile hydrothermal process at 180 °C for 10 h. α-(NH₄)₆-P₂Mo₁₈O₆₂·nH₂O, one of polyoxometalates with Dawson structure, was employed as the source of molybdates. The diameter and length of the obtained SrMoO₄ nanowires are about 20 nm and 5-10 μm, respectively. HRTEM results show that the SrMoO₄ nanowires are of high crystallinity with rough surface. However, when Na₂MoO₄·2H₂O was used, there are only SrMoO₄ nanorods with smaller aspect ratio (200/70 nm) in the similar hydrothermal process. The probable growth mechanism was discussed.     

Synthesis of nanocrystalline material by sputtering and laser ablation at low temperatures

Physical vapor deposition techniques such as sputtering and laser ablation – which are very commonly used in thin film technology – appear to hold much promise for the synthesis of nanocrystalline thin films as well as loosely aggregated nanoparticles. We present a systematic study of the process parameters that facilitate the growth of nanocrystalline metals and oxides. The systems studied include TiO₂, ZnO, γ-Al₂O₃, Cu₂O, Ag and Cu. The mean particle size and crystallographic orientation are influenced mainly by the sputtering power, the substrate temperature and the nature, pressure and flow rate of the sputtering gas. In general, nanocrystalline thin films were formed at or close to 300 K, while loosely adhering nanoparticles were deposited at lower temperatures. Received: 31 October 2000 / Accepted: 9 January 2001 / Published online: 26 April 2001     

Structure and magnetic properties of the oxide layers on iron ultrafine particles

5 . The γ-Fe particles, because of their paramagnetic nature, are very convenient for investigation on the attributes of iron oxide layers formed on the particle surfaces. Structures, morphologies and magnetic properties of the oxide layers covering the iron ultrafine particles have been studied using transmission electron microscopy observation, magnetic property measurement, X-ray diffraction and annealing treatment. Convincing evidences established that the iron oxide layers are not continuous and consist of very fine crystallites, and that these layers are non-ferromagnetic and have no contribution to the saturation magnetization of the iron particles. The iron oxide layers formed at room temperature was determined to be Fe₃O₄. Additionally, a brief annealing of the iron particles in air were performed to examine magnetic properties of the formed iron oxide layers and ultrafine oxide particles. Received: 30 April 1996/Accepted: 5 November 1996     

Third-Order Nonlinear Optical Susceptibility of Indium Phosphide Nanocrystals

InP nanocrystals synthesized by refluxing and annealing of organic solvent are determined from XRD measurements to have an averse granularity of 25 nm. The nonlinear optical properties of the InP nanocrystals studied by using laser Z-scan technique with 50 ps pulses at 532nm are found to reveal strong nonlinear optical properties and two-photon absorption phenomenon. Also, the nonlinear absorption coeffcient, the nonlinear refractive index and the third-order nonlinear optical susceptibility are determined by experiments, in which the nonlinear refractive index is three orders of magnitude larger than that of bulk InP.