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排序方式: 共有140条查询结果,搜索用时 15 毫秒
1.
Room temperature, high-yield synthesis of multiple shapes of gold nanoparticles in aqueous solution 总被引:10,自引:0,他引:10
A seed-mediated growth method was used to control the morphology and dimensions of Au nanocrystals by the manipulation of the experimental parameters in aqueous solution at room temperature. This chemical route produces various structural architectures with rod-, rectangle-, hexagon-, cube-, triangle-, and starlike profiles and branched (such as bi-, tri-, tetra-, and multipod) Au nanocrystals of various dimensions in high yield in the presence of a single surfactant, cetyltrimethylammonium bromide. 相似文献
2.
A computational study of hydration, solution structure, and dynamics in dilute carbohydrate solutions 总被引:1,自引:0,他引:1
We report results from a molecular simulation study of the structure and dynamics of water near single carbohydrate molecules (glucose, trehalose, and sucrose) at 0 and 30 degrees C. The presence of a carbohydrate molecule has a number of significant effects on the microscopic water structure and dynamics. All three carbohydrates disrupt the tetrahedral arrangement of proximal water molecules and restrict their translational and rotational mobility. These destructuring effects and slow dynamics are the result of steric constraints imposed by the carbohydrate molecule and of the ability of a carbohydrate to form stable H bonds with water, respectively. The carbohydrates induce a pronounced decoupling between translational and rotational motions of proximal water molecules. 相似文献
3.
R. Anjibabu Samaresh Sau B. Jagan Mohan Reddy Rajkumar Banerjee B.V. Subba Reddy 《Tetrahedron letters》2013
A variety of aldehydes undergo a smooth coupling with (4-methylcyclohex-3-en-1-yl)methanol in the presence of 2 mol % of phosphomolybdic acid in dichloromethane to afford 3-oxabicyclo[3.3.1]non-7-ene in good yields through 3,5-oxonium-ene cyclization under mild conditions. The use of inexpensive, nontoxic, and readily available heteropoly acid catalyst makes this method simple, convenient, and environmental-friendly. 相似文献
4.
Self-injection length in La0.7Ca0.3MnO3-YBa2Cu3O7-δ ferromagnet-superconductor multilayer thin films
We have carried out extensive studies on the self-injection problem in barrierless heterojunctions between La0.7Ca0.3MnO3 (LCMO) and YBa2Cu3O7-δ (YBCO) thin films. The heterojunctions were formed in situ by sequentially growing LCMO and YBCO films on 〈100〉 LaAlO3 (LAO) substrate using a pulsed laser deposition (PLD) system. YBCO micro-bridges with 64 μm width were patterned both on
the LAO (control) and LCMO side of the substrate. Critical current, I
c, was measured at 77 K on both the control side as well as the LCMO side for different YBCO film thickness. It was observed
that while the control side showed a J
c of ∼ 2 × 106 A/cm2, the LCMO side showed about half the value for the same thickness (1800 ?). The difference in J
c indicates that a certain thickness of YBCO has become ‘effectively’ normal due to self-injection. From the measurement of
J
c at two different thicknesses (1800 ? and 1500 ?) of YBCO films both on the LAO as well as the LCMO side, the value of self-injection
length (at 77 K) was estimated to be ∼ 900 ?. To the authors’ best knowledge, this is the first time that self-injection length
has been quantified. A control experiment carried out with LaNiO3 deposited by PLD on YBCO did not show any evidence of self-injection. 相似文献
5.
Bias dependent scanning tunneling microscopy and scanning tunneling spectroscopy have been used to characterize the influence of transverse electric fields on the electronic properties of boron-nitride nanotubes (BNNTs). We find experimental evidence for the theoretically predicted giant Stark effect. The observed giant Stark effect significantly reduces the band gap of BNNTs and thus greatly enhances the utility of BNNTs for nanoscale electronic, electromechanical, and optoelectronic applications. 相似文献
6.
An orthonormalization method suitable to deal with an overcomplete and non-orthogonal set of vectors is derived. It is then used to obtain the orthonormal set of states connected with the angular momentum coupling of N fermions in a single j-shell. 相似文献
7.
Murphy CJ Sau TK Gole AM Orendorff CJ Gao J Gou L Hunyadi SE Li T 《The journal of physical chemistry. B》2005,109(29):13857-13870
This feature article highlights work from the authors' laboratories on the synthesis, assembly, reactivity, and optical applications of metallic nanoparticles of nonspherical shape, especially nanorods. The synthesis is a seed-mediated growth procedure, in which metal salts are reduced initially with a strong reducing agent, in water, to produce approximately 4 nm seed particles. Subsequent reduction of more metal salt with a weak reducing agent, in the presence of structure-directing additives, leads to the controlled formation of nanorods of specified aspect ratio and can also yield other shapes of nanoparticles (stars, tetrapods, blocks, cubes, etc.). Variations in reaction conditions and crystallographic analysis of gold nanorods have led to insight into the growth mechanism of these materials. Assembly of nanorods can be driven by simple evaporation from solution or by rational design with molecular-scale connectors. Short nanorods appear to be more chemically reactive than long nanorods. Finally, optical applications in sensing and imaging, which take advantage of the visible light absorption and scattering properties of the nanorods, are discussed. 相似文献
8.
Nour-Mohhamadi F Nguyen SD Boschloo G Hagfeldt A Lund T 《The journal of physical chemistry. B》2005,109(47):22413-22419
The oxidative degradation rate, kdeg, of the solar cell dye (Bu4N+)2[Ru(dcbpyH)2(NCS)2]2-, referred to as N719 or [RuL2(NCS)2], was obtained by applying a simple model system. Colloidal solutions of N719-dyed TiO2 particles in acetonitrile were irradiated with 532-nm monochromatic light, and the sum of the quantum yields for the oxidative degradation products [RuL2(CN)2], [RuL2(NCS)(CN)], and [RuL2(NCS)(ACN)], Phideg, was obtained at eight different light intensities in the range of 0.1-16.30 mW/cm2 by LC-UV-MS. The Phideg values decreased from 3.3 x 10-3 to 2.0 x 10-4 in the applied intensity range. By using the relation kdeg = Phidegkback and back electron-transfer reaction rates, kback, obtained with photoinduced absorption spectroscopy, it was possible to calculate an average value for the oxidative degradation rate of N719 dye attached to TiO2 particles, kdeg = 4.0 x 10-2 s-1. The stability of N719 dye during solar cell operation was discussed based on this number, and on values of the electron-transfer rate between [Ru(III)L2(NCS)2] and iodide ion that are available in the literature. 相似文献
9.
Angelie E Sappey-Marinier D Mallet J Bonmartin A Sau J 《Magnetic resonance imaging》2000,18(5):625-633
Magnetic resonance spectroscopic imaging is limited by a low signal-to-noise ratio, so a compromise between spatial resolution and examination time is needed in clinical application. The reconstruction of truncated signal introduces a Point Spread Function that considerably affects the spatial resolution. In order to reduce spatial contamination, three methods, applied after Fourier transform image reconstruction, based on deconvolution or iterative techniques are tested to decrease Point Spread Function contamination. A Gauss-Seidel (GS) algorithm is used for iterative techniques with and without a non-negative constraint (GS+). Convergence and noise dependence studies of the GS algorithm have been done. The linear property of contamination was validated on a point sample phantom. A significant decrease of contamination without broadening the spatial resolution was obtained with GS+ method compared to a conventional apodization. This post-processing method can provide a contrast enhancement of clinical spectroscopic images without changes in acquisition time. 相似文献
10.