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Sekar P Greyson EC Barton JE Odom TW 《Journal of the American Chemical Society》2005,127(7):2054-2055
This communication describes a new synthetic approach to one- (1D) and two-dimensional (2D) NbSe2 nanoscale materials using soft chemical methods. Our one-pot synthesis provides a direct route to control the morphology of nanostructures that can exhibit complex electronic properties, and can produce layered, nanocrystalline materials in high yield. 相似文献
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da Costa EC Figueiredo W 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》2000,61(2):1134-1138
We studied in this work a three-monomer reaction model on one- and two-dimensional lattices. We have taken different reactivity rates among pairs of monomers and the reaction between two selected monomers was forbidden. We have employed the mean field and the pair approximation to decouple the equations of motion for the densities of single and pairs of monomers. We found the stationary states and the phase diagram of the model. We have shown that, in two dimensions and within the pair approximation, there is a first-order transition line between active and poisoned steady states. 相似文献
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da Rocha ZN Ferreira KQ Silva M de Oliveira EC Chiericato G Tfouni E 《Inorganic chemistry》2001,40(21):5385-5392
The synthesis, UV-vis spectra, and electrochemical behavior of the nitrile-bonded trans-[Ru(II)Cl(cyclam)(4-NCpyH(+))](BF(4))(2) (4-Ncpy = 4-cyanopyridine; cyclam = 1,4,8,11-tetraazacyclotetradecane) and of trans-[Ru(III)Cl(cyclam)(NHC(O)-4-pyH(+))](2+) are described. The UV-vis spectrum of the Ru(II) nitrile complex shows a MLCT band at 548 nm at pH 1, which is shifted to 440 nm at pH approximately 6, for the unprotonated species. trans-[Ru(II)Cl(cyclam)(4-NCpyH(+))](2+) was electrolytically oxidized (+600 mV vs Ag/AgCl) at pH 1 to Ru(III), followed by hydrolysis (k = 0.25 s(-1)) of the coordinated nitrile to give trans-[Ru(III)Cl(cyclam)(NHC(O)-4-pyH(+))](2+), in which the amide is deprotonated and coordinated through nitrogen. The identity of the species is pH dependent, the nitrogen-bonded amide prevailing at low pH (< 7), but the oxygen-bonded amide is formed through linkage isomerization at higher pH (>8). Reduction of trans-[Ru(III)Cl(cyclam)(NHC(O)-4-pyH)](2+) in acidic media does not result in fast aquation (k = approximately 2.4 x 10(-5) s(-1)) as for other amides on ruthenium(II) pentaammine, but instead linkage isomerization occurs, resulting in the oxygen-bonded species, with an estimated rate constant of approximately 2 x 10(-2) s(-1), smaller than in the pentaammine analogues. 相似文献
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This concepts article describes our developments in nanopatterning related to photonics. We have a nanopatterning toolkit that can generate functional, nanostructured surfaces at nm-length scales and over cm2-areas in a single (or small number of) step(s). This paper will focus on three examples of surface-patterned nanostructures and their optical properties: (i) one-dimensional arrays of metallic nanoparticles; (ii) arrays of small-diameter ZnO nanowires; (iii) mesoscale structures of CdSe/ZnS nanocrystals. The potential for advances in nanopatterning to contribute to a broad range of light-based applications will be discussed. 相似文献
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Giessing AM Scott LG Kirpekar F 《Journal of the American Society for Mass Spectrometry》2011,22(7):1242-1251
LC/MS analysis of ribonucleosides is traditionally performed by reverse phase chromatography on silica based C18 type stationary
phases using MS compatible buffers and methanol or acetonitrile gradients. Due to the hydrophilic and polar nature of nucleosides,
down-scaling C18 analytical methods to a two-column nano-flow setup is inherently difficult. We present a nano-chip LC/MS
ion-trap strategy for routine characterization of RNA nucleosides in the fmol range. Nucleosides were analyzed in positive
ion mode by reverse phase chromatography using a 75 μ × 150 mm, 5 μ particle porous graphitic carbon (PGC) chip with an integrated
9 mm, 160 nL trapping column. Nucleosides were separated using a formic acid/acetonitrile gradient. The method was able to
separate isobaric nucleosides as well as nucleosides with isotopic overlap to allow unambiguous MS
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identification on a low resolution ion-trap. Synthesis of 5-hydroxycytidine (oh5C) was achieved from 5-hydroxyuracil in a novel three-step enzymatic process. When operated in its native state using formic
acid/acetonitrile, PGC oxidized oh5C to its corresponding glycols and formic acid conjugates. Reduction of the PGC stationary phase was achieved by flushing
the chip with 2.5 mM oxalic acid and adding 1 mM oxalic acid to the online solvents. Analyzed under reduced chromatographic
conditions oh5C was readily identified by its MH+
m/z 260 and MSn fragmentation pattern. This investigation is, to our knowledge, the first instance where oxalic acid has been used as an
online reducing agent for LC/MS. The method was subsequently used for complete characterization of nucleosides found in tRNAs
using both PGC and C18 chips. 相似文献
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