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排序方式: 共有838条查询结果,搜索用时 274 毫秒
61.
本文介绍在分子束外延系统中,沿[311]面原位生长GaAs/AIAs量子线结构的一种简单方法及其拉曼和发光特性。这一方法能克服目前纳米尺度光刻技术的困难,因此,是一种制备低维样品的有希望的方法。 相似文献
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A novel cedar-like Au nanoparticles (AuNPs) coating was fabricated on an etched stainless steel (SS) wire by direct chemical deposition and used as an efficient and unbreakable solid phase microextraction (SPME) fiber. The etched SS wire offers a rough surface structure for subsequent growth of AuNPs in chloroauric acid solution. As a result, the uniform cedar-like AuNPs coating with larger surface area was tightly attached to the etched SS wire substrate. The AuNPs coated etched SS fiber (AuNPs/SS) was examined for SPME of ultraviolet (UV) filters, phthalate esters and aromatic hydrocarbons coupled to high-performance liquid chromatography with UV detection. The fabricated fiber exclusively exhibited excellent extraction efficiency and selectivity for some aromatic hydrocarbons. Influential parameters of extraction and desorption time, temperature, stirring rate and ionic strength were investigated and optimized. The limits of detection ranged from 0.008 μg L−1 to 0.037 μg L−1. The single fiber repeatability varied from 3.90% to 4.50% and the fiber-to-fiber reproducibility ranged from 5.15% to 6.87%. The recovery of aromatic hydrocarbons in real water samples spiked at 2.0 μg L−1 and 20 μg L−1 ranged from 94.38% to 106.2% with the relative standard deviations below 6.44%. Furthermore the growth of the cedar-like AuNPs coating can be performed in a highly reproducible manner. This fabricated fiber exhibits good stability and withstands at least 200 extraction and desorption replicates. 相似文献
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采用激光剥蚀电感耦合等离子体质谱法测定纯铝及铝丝中铁、硅、铜、锰、镁、钛、锌、铬和镍的含量。采用低功率等离子体,以27Al为内标。样品直径为0.5~3 mm时,直径粗细与元素的信号不相关。所有元素的分馏因子在0.94~1.13之间时,可以认为没有分馏效应;纯铝和铝合金的基体效应不明显,铸铝会影响基体效应。测定了块状和丝状标准物质,测定值与认定值基本吻合,纯铝板的测定值与直读光谱法测定结果相一致。受背景干扰的影响,测定值的相对标准偏差(n=5)在2.9%~32%之间。 相似文献
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《Electroanalysis》2017,29(2):497-505
An electrochemical sensor for the simultaneous and sensitive detection of Cd(II) and Pb(II) is proposed on the basis of square‐wave anodic stripping voltammetry (SWASV) experiments using a novel bismuth film/ordered mesoporous carbon‐molecular wire modified graphite carbon paste electrode (Bi/OMC‐MW/GCPE). Ordered mesoporous carbon (OMC) and molecular wire (MW) (diphenylacetylene) were used as the modifier and binder, respectively. The Bi/OMC‐MW/GCPE was prepared with the addition of graphite powder, OMC and DPA at the ratio of 2 : 1 : 1. The electrochemical properties and morphology of the electrode were characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), SWASV and scanning electron microscopy (SEM). The parameters affecting the stripping current response were investigated and optimized. The experimental results show that the prepared electrode exhibited excellent electrochemical performance, good electrical conductivity and a high stripping voltammetric response. Under optimized conditions, a linear range was achieved over a concentration range from 1.0 to 70.0 μg/L for both Cd(II) and Pb(II) metal ions, with detection limits of 0.07 μg/L for Cd(II) and 0.08 μg/L for Pb(II) (S/N=3) with the deposition time 150 s. Moreover, the sensor exhibited improved sensitivity and reproducibility compared to traditional CPEs. The fabricated electrode was then successfully used to satisfactorily detect Cd(II) and Pb(II) in real soil samples. 相似文献
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A. P. Brylyakov G. M. Zharkova B. Yu. Zanin V. N. Kovrizhina D. S. Sboev 《Journal of Applied Mechanics and Technical Physics》2004,45(4):510-516
The flow structure behind wire grids is studied for flows with a low subsonic velocity, and the effect of grids on the boundarylayer flow structure is considered. It is shown that the meanvelocity inhomogeneity induced by the grid does not disappear until a distance of 925 calibers downstream of the grid is reached. Liquidcrystal thermography combined with hotwire measurements made it possible to find the source of steady largescale streamwise vortex structures in the boundary layer on a wedge and on an airfoil and to determine the parameters of these structures. 相似文献
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考虑铁基超导中能带间的相互作用和界面对每一个能带的散射作用, 利用推广的Blonder-Tinkham-Klapwijk模型, 并通过求解Bogoliubov-de Gennes 方程研究了具有不同类型双能隙系统的量子线/铁基超导隧道结中准粒子的输运系数和隧道谱. 研究表明: 1)在弹道极限时, 随着带间相互作用的增大, s± 波隧道谱中零偏压附近的平台演变成电导峰; s++ 波的平台演变成凹陷; p波的零偏压电导峰被压低. 2)界面对两个能带的散射作用不为零时, 随着带间相互作用的增大, s± 波和s++ 波两能隙处的峰值将降低, 而两峰间的凹陷值将变大; p波的零偏压电导峰被压低, 非零偏压电导增大. 3)界面对每个能带的散射, 可使其产生的电导峰变得更加尖锐, 但可压低和抹平另一个带产生的电导峰值. 这些结果对于澄清铁基超导体的能隙结构和区别不同类型铁基超导体有所帮助. 相似文献
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Molecular photonics is a rapidly developing and multi-disciplinary field of research involving the construction of molecular assemblies comprising photoactive building blocks that are responsive to a light stimulus. A salient challenge in this field is the controlled assembly of these building blocks with nanoscale precision. DNA exhibits considerable promise as an architecture for the templated assembly of photoactive materials. In this Concept Article we describe the progress that has been made in the area of DNA photonics, in which DNA acts as a platform for the construction of optoelectronic assemblies, thin films and devices. 相似文献
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