Search

The authors report the preparation of silica nanotubes by a simple two-stage thermal evaporation of ZnSe and SiO powders. Firstly, nanocables with single crystalline ZnSe nanowire cores and amorphous SiO2 shells were formed by a combined vapor-liquid-solid and SiO-assisted growth process. The ZnSe cores were then evaporated at high temperatures leaving behind SiO2 nanotubes. As-fabricated SiO2 nanotubes were studied with scanning electron microscopy, transmission electron microscopy, energy-dispersive x-ray spectroscopic analysis, and photoluminescence measurement. The SiO2 nanotubes were found to be amorphous, diameter uniform, smooth, and rigid. This method can be used to prepare other materials and morphology-controlled nanotubes. [ABSTRACT FROM AUTHOR]

Nanometer-sized coaxial cables with a single-crystal ZnS core and a thin amorphous SiO2 shell were synthesized by simple thermal evaporation in vacuum. As-fabricated ZnS/SiO2 nanocables were studied using scanning electron microscopy, x-ray diffraction and transmission electron microscopy. The ZnS/SiO2 nanocables have diameters of ∼50 nm, lengths of several tens of micrometers, and shell thickness of ∼4 nm. The core of the nanocable has a wurtzite structure with a growth direction along [001]. The nanocables show strong photoluminescence with two peaks related to band gap and defect-related emission. [ABSTRACT FROM AUTHOR]

Large-scale uniform silicon nanowires (SiNWs) array was fabricated by chemical etching on n-Si(111) wafer. Silver nanoparticles (AgNPs) were loaded on their surfaces. The AgNPs on SiNWs (AgNPs@SiNWs) array exhibit strong surface-enhanced Raman effect. On the substrate surfaces, characteristic Raman signals are generated with trace amount of mouse immunoglobulin G (mIgG), goat-anti-mouse immunoglobulin G (gamIgG), and immune complexes formed from 4 ng each of mIgG and gamIgG. The shifted positions and changed intensities in Raman bands indicate the occurrence of immunoreactions. This AgNPs@SiNWs array is a unique substrate for surface-enhanced Raman spectroscopy to show the immune reagents and immunoreactions at higher sensitivity. [ABSTRACT FROM AUTHOR]

The stability and performance of tokamak plasmas are routinely limited by various magnetohydrodynamic instabilities, such as neoclassical tearing modes (NTMs). This paper presents a rather simple method to control the NTMs in real time (RT) on a tokamak, including the control principle of a feedback approach for RT suppression and stabilization for the NTMs. The control system combines Mirnov, electron cyclotron emission, and soft X-ray diagnostics used for determining the NTM positions. A methodology for fast detection of 2/1 or 3/2 NTM positions with 129 x 129 grid reconstruction is elucidated. The forty poloidal angles for steering the electron cyclotron resonance heating (ECRH)/electron cyclotron current drive launcher are used to establish the alignment of antenna mirrors with the center of the NTM and to ensure launcher emission intersecting with the rational surface of a magnetic island. Pilot experiments demonstrate the RT control capability to trace the conventional tearing modes (CTMs) in the HL-2A tokamak. The 2/1 CTMs have been suppressed or stabilized by the ECRH power deposition on site or with the steerable launcher. [ABSTRACT FROM AUTHOR]

Large-scale arrays of highly oriented single-crystal ZnO nanotubes (ZNTs) are successfully fabricated on transparent conductive substrates by a simple method from an aqueous solution at a low temperature (typically 85 °C). The tubular morphology of the ZnO nanostructures is formed by a defect-selective chemical etching of the electrodeposited ZnO nanorods. The size of the ZNT arrays is determined by that of ZnO nanorod arrays which can be readily controlled by tuning several electrodeposition parameters. The present method can be employed to prepare ZNT arrays on flexible, conductive substrates, as well as on patterned conductive substrates. [ABSTRACT FROM AUTHOR]