Synthesis and properties of ZnO nano-ribbon and comb structures

ZnO is of great interest for photonic applications due to its wide band gap (3.37 eV) and large exciton binding energy (60 meV). A large variety of fabrication methods and nanostructure morphologies was reported up to date for this material. Obtained morphologies include nanobelts or nanoribbons, nanowires, nanorods, tetrapod nanostructures, etc. Novel nanostructures like hierarchical nanostructures, nanobridges and nanonails have also been fabricated. In this work, we report a simple method for fabrication of nanoribbon and nanocomb structures. The structures are fabricated by evaporation of a mixture of ZnO and carbon nanotubes (CNT) at 1050°C, and the deposition products have been collected on Si substrates in the temperature range 750-800°C. The growth mechanism of obtained structures is discussed. © 2005 American Institute of Physics.published_or_final_versio

Time-dependent density functional theory quantum transport simulation in non-orthogonal basis

Basing on the earlier works on the hierarchical equations of motion for quantum transport, we present in this paper a first principles scheme for time-dependent quantum transport by combining time-dependent density functional theory (TDDFT) and Keldysh's non-equilibrium Green's function formalism. This scheme is beyond the wide band limit approximation and is directly applicable to the case of non-orthogonal basis without the need of basis transformation. The overlap between the basis in the lead and the device region is treated properly by including it in the self-energy and it can be shown that this approach is equivalent to a lead-device orthogonalization. This scheme has been implemented at both TDDFT and density functional tight-binding level. Simulation results are presented to demonstrate our method and comparison with wide band limit approximation is made. Finally, the sparsity of the matrices and computational complexity of this method are analyzed.published_or_final_versio

Growth of N, N′-di(naphthalene-1-yl)-N, N′-diphenyl-benzidine dome structures

N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine samples exhibiting interesting nano/microstructure were fabricated by thermal evaporation in a tube furnace under Ar gas flow. We investigated the influence of the substrate type, substrate temperature, source temperature, and the gas flow rate on the obtained morphology. The deposited material was investigated using scanning electron microscopy, x-ray diffraction, and photoluminescence. We found that the substrate temperature was the factor which significantly affected the obtained morphology, while other factors such as substrate type, source temperature, and gas flow mainly affected the size distribution of the features but not the type of morphology observed. © 2005 American Institute of Physics.published_or_final_versio

Reaction pathways and mechanisms of the electrochemical degradation of phenol on different electrodes

Laboratory experiments were carried out on the kinetics and pathways of the electrochemical (EC) degradation of phenol at three different types of anodes, Ti/SnO2-Sb, Ti/RuO2, and Pt. Although phenol was oxidised by all of the anodes at a current density of 20 mA/cm2 or a cell voltage of 4.6 V, there was a considerable difference between the three anode types in the effectiveness and performance of EC organic degradation. Phenol was readily mineralized at the Ti/SnO2-Sb anode, but its degradation was much slower at the Ti/RuO2 and Pt anodes. The analytical results of high-performance liquid chromatography (HPLC) and gas chromatography coupled with mass spectrometry (GC/MS) indicated that the intermediate products of EC phenol degradation, including benzoquinone and organic acids, were subsequently oxidised rapidly by the Ti/SnO2-Sb anode, but accumulated in the cells of Ti/RuO2 and Pt. There was also a formation of dark-coloured polymeric compounds and precipitates in the solutions electrolyzed by the Ti/RuO2 and Pt anodes, which was not observed for the Ti/SnO 2-Sb cells. It is argued that anodic property not only affects the reaction kinetics of various steps of EC organic oxidation, but also alters the pathway of phenol electrolysis. Favourable surface treatment, such as the SnO2-Sb coating, provides the anode with an apparent catalytic function for rapid organic oxidation that is probably brought about by hydroxyl radicals generated from anodic water electrolysis. © 2005 Elsevier Ltd. All rights reserved.postprin

ZnO nanostructures prepared from ZnO:CNT mixtures

Due to its wide band gap (3.37 eV) and large exciton binding energy (60 meV), ZnO is of great interest for photonic applications. A number of different morphologies, such as nanobelts, nanowires, tetrapod nanostructures, tubular nanostructures, hierarchical nanostructures, nanobridges, nanonails, oriented nanorod arrays, nanoneedles, nanowalls, and nanosheets, were reported. A range of synthesis methods for fabrication of ZnO nanostructures was reported as well. A common method is evaporation from mixture of ZnO and carbon, which is usually in the form of graphite. In this work, we studied the morphology of the ZnO nanostructures fabricated from the mixture of ZnO (micron-sized and nanoparticles) and carbon (graphite, single-wall carbon nanotubes). When graphite and ZnO powders were used, tetrapod structures were obtained. If one of the reactants was nanosized, the diameter of the tetrapod arms was no longer constant. Finally, when both reactants were nanosized, novel morphologies were obtained. We studied the dependence of the morphology on the amount of starting material and the type of carbon used. The ZnO nanostructures were studied using field emission scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and X-ray diffraction. Growth mechanism and factors affecting the morphologies are discussed.published_or_final_versio

High expression of biglycan is associated with poor prognosis in patients with esophageal squamous cell carcinoma

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Time-dependent density functional theory for open systems with a positivity-preserving decomposition scheme for environment spectral functions

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Allelopathy of root exudates from different resistant eggplants to Verticillium dahliae and the identification of allelochemicals

Three eggplant cultivars were inoculated with Verticillium dahliae Kleb. to assess their resistance to Verticillium wilt. Solanum tor was resistant, “Liyuanziqie” was tolerant, and “Xi’anlvqie” susceptible. The disease incidence and disease index of Verticillium wilt and the amount of V. dahliae in rhizospheric soil, variation of microbial composition, the allelopathy of root exudates to mycelium growth of V. dahliae and the chemical substances of root exudates from eggplant cultivars with different resistance to Verticillium wilt were investigated in this experiment. The results showed that the root exudates of resistant type could not only affect the growth and development of V. dahliae, but also influence V. dahliae indirectly through regulating soil microbial community composition. This may be one of the reasons for the increase of disease resistance. However, the susceptible type exhibited an opposite trend. It was inferred that the resistant type contained some particular components, such as  acohd, amide, pyranoid, fluorene, while the susceptible one comprised more types of components, that is, ketone, phenol, ester and phenolic acid.Key words: Allelopathy, allelochemical, root exudates, eggplant, Verticillium dahliae, Verticillium wilt, microbial composition

Design and Testing of Cesium Atomic Concentration Detection System Based on TDLAS

In order to better build the Neutral Beam Injector with Negative Ion Source (NNBI), the pre-research on key technologies has been carried out for the Comprehensive Research Facility for Fusion Technology (CRAFT). Cesium seeding into negative-ion sources is a prerequisite to obtain the required negative hydrogen ion. The performance of ion source largely depends on the cesium conditions in the source. It is very necessary to quantitatively measure the amount of cesium in the source during the plasma on and off periods (vacuum stage). This article uses the absorption peak of cesium atoms near 852.1nm to build a cesium atom concentration detection system based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) technology. The test experiment based on the cesium cell is carried out, obtained the variation curve of cesium concentration at different temperatures. The experimental results indicate that: the system detection range is within 5*10E6-2.5*10E7 pieces/cm3 and the system resolution better than 1*10E6 pieces/cm3.Comment: 8 pages,7 figures, the 20th International Symposium on Laser-Aided Plasma Diagnostic

Green photoluminescence in ZnO nanostructures

In photoluminescence (PL) spectrum of ZnO, typically one or more peaks in the visible spectral range due to defect emission can be observed in addition to one UV peak due to band edge emission. The origin of the defect emission is controversial and several mechanisms have been proposed. In this work, we fabricated ZnO nanostructures with different methods (evaporation and chemical synthesis). We found that the preparation method influences the peak position of the defect emission. Different hypotheses for the origin of the green emission in our nanostructured samples are discussed. © 2005 American Institute of Physics.published_or_final_versio