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An understanding of the structure and behavior of electrolyte solutions in nanoenvironements is crucial not only for a wide variety of applications, but also for the development of physical, chemical, and biological processes. We demonstrate the structure and stability of electrolyte in carbon nanotubes using hybrid reverse Monte Carlo simulations of X‐ray diffraction patterns. Hydrogen bonds between water are adequately formed in carbon nanotubes, although some hydrogen bonds are restricted by the interfaces of carbon nanotubes. The hydrogen bonding network of water in electrolyte in the carbon nanotubes is further weakened. On the other hand, formation of the ion hydration shell is significantly enhanced in the electrolyte in the carbon nanotubes in comparison to ion hydration in bulk electrolyte. The significant hydrogen bond and hydration shell formation are a result of gaining stability in the hydrophobic nanoenvironment.  相似文献   

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Water surrounded by hydrophobic interfaces affects a variety of chemical reactions and biological activities. Carbon nanotubes (CNTs) can be used to investigate the behavior of water at hydrophobic interfaces. Here, we determined the fundamental unit of water by evaluating the ice‐like cluster formation of water in the limited hydrophobic nanospaces of CNTs, using X‐ray diffraction and molecular simulation analysis. The water in CNTs with a diameter of 1 nm had fewer hydrogen bonds than bulk water under ambient conditions. In CNTs with diameters of 2 and 3 nm, water formed nanoclusters even under ambient conditions, because of prolific hydrogen bonding; predominant ice‐like cluster formation was induced in the 2–3 nm nanospaces. The results confirming the cluster formation in the CNTs also demonstrated that the critical cluster size was 0.8–3.4 nm. The fundamental cluster size was 0.8 nm; these results indicated that 0.8 nm clusters are the fundamental units of water assemblies.  相似文献   

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Size‐controlled and ordered assemblies of artificial nanotubes are promising for practical applications; however, the supramolecular assembly of such systems remains challenging. A novel strategy is proposed that can be used to reinforce intermolecular noncovalent interactions to construct hierarchical supramolecular structures with fixed sizes and long‐range ordering by introducing ionic terminals and fully rigid arms into benzene‐1,3,5‐tricarboxamide (BTA) molecules. A series of similar BTA molecules with distinct terminal groups and arm lengths are synthesized; all form hexagonal bundles of helical rosette nanotubes spontaneously in water. Despite differences in molecular packing, the dimensions and bundling of the supramolecular nanotubes show almost identical concentration dependence for all molecules. The similarities of the hierarchical assemblies, which tolerate certain molecular irregularities, can extend to properties such as the void ratio of the nanotubular wall. This is a rational strategy that can be used to achieve supramolecular nanotubes in aqueous environments with precise size and ordering at the same time as allowing molecular modifications for functionality.  相似文献   

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A synthetic study to disclose the more appropriate manner by which two calix[6]arene units could be connected for the construction of an extended tubular structure was undertaken. As a result, a head-to-tail double calix[6]arene having the structure of an oriented nanotube that is about 2.6 nm long and 1.6 nm wide was prepared and characterized. This molecule is able to act as a wheel-type host and forms a supramolecular complex with an axle-type molecule, derived from 4,4'-bipyridinium (viologen), through very efficient self-assembly in solution. The properties of such a pseudorotaxane-type complex, which is stabilized by a combination of noncovalent interactions, were investigated in solution by UV/Vis absorption spectroscopy and voltammetric methods. These observations provide a clue about the location of the bipyridinium unit along the nanotube. In the solid state, the complex undergoes a further stage of self-assembly, thereby initiating extended oriented tubular structures. Crystallographic studies revealed that the positioning of the viologen dication in this asymmetric wheel is addressed by a complicated pattern of cooperative noncovalent intermolecular interactions that involve only one half of the host, whereas the remaining (more polar) half of the host is exploited to create long-range structural order that leads to a "secondary" structure of extended supramolecular channels that, in turn, self-assemble in the lattice, thus giving rise to a "tertiary" structure of parallel sandwiches of nanotubes.  相似文献   

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We demonstrate that graphite powder and multiwalled carbon nanotubes (MWCNTs) can be derivatised by 4-nitrobenzylamine (4-NBA) simply by stirring the graphite powder or MWCNTs in a solution of acetonitrile containing 10 mM 4-NBA. We propose that 4-NBA partially intercalates at localised edge-plane or edge-plane-like defect sites and this hypothesis with a range of experimental data provided by electrochemistry in both aqueous and nonaqueous media, electron microscopy and X-ray powder diffraction.  相似文献   

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Motivated by the need for new phosphors of white light emitting diode (WLED) application, Ca0.95Nb2 O6:Eu3+0.05 phosphors were synthesized by high temperature solid‐state reaction. Increasing the content of doped‐Eu3+ and adding the co‐activator Bi3+ to improve the photoluminescence (PL) intensity of Ca1?xNb2 O6Eu3+x phosphors were investigated in detail. The effects of Eu3+ were better than that of Bi3+ on the PL intensity of Ca1?xNb2 O6Eu3+x phosphors. Compared with Y2O2 S:0.05Eu3+ the Ca0.70Nb2 O6:Eu3+0.03 phosphor could be excited efficiently by UV (395 nm) light and emit the red light at 614 nm with line spectra, which were coupled well with the characteristic emission from UV‐Near UV LED. The CIE (International Commission on Illumination) chromaticity coordinates (x?0.654, y?0.348) of Ca0.70Nb2O6:Eu3+0.03 were close to the NTSC (National Television Standard Committee) standard values. Therefore Ca0.70Nb2 O6:Eu3+0.03 might find application to UV‐Near UV InGaN chip‐based white light emitting diodes, which is further proved by the LED fabrication with the Ca0.70Nb2 O6:Eu3+0.03 phosphor.  相似文献   

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Synthesis and Structure of Pentaalkylchlorohexastibane Sb6R5Cl [R = (Me3Si)2CH] The reaction of RSbCl2 [R = (Me3Si)2CH] with Na‐K alloy in tetrahydrofuran gives besides the known rings SbnRn (n = 3, 4), (Me3Si)2CH2 and the pentaalkylchlorohexastibane Sb6R5Cl ( 1 ). 1 was characterized by spectroscopic methods (MS, 1H‐, 13C‐NMR, X‐ray diffraction). The structure of 1 consists of a folded four membered antimony ring in the all‐trans configuration with three alkyl groups and one Sb(R)—Sb(R)Cl fragment as substituents.  相似文献   

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The modification of coatings resins by graft polymerization of vinylidene chloride should produce a coatings binder with improved barrier properties. For superior color stability, vinylidene chloride must be copolymer-ized with other monomers such as alkyl acrylates and methacrylates. Ceric ion initiation was used to graft vinylidene chloride free-radically onto a model alcohol-containing polymer, polyvinyl alcohol. The effects of various reaction parameters on vinylidene chloride grafting were studied. Graft copolymers were characterized using selective solvent extraction, FTIR, SEM, XES, DSC, and x-ray diffraction.  相似文献   

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Supercritical growth: The formation and evolution of ceria nanoparticles during hydrothermal synthesis was investigated by in?situ total scattering and powder diffraction. The nucleation of pristine crystalline ceria nanoparticles originated from previously unknown cerium dimer complexes. The nanoparticle growth was highly accelerated under supercritical conditions.  相似文献   

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Single‐walled carbon nanotubes (SWNTs) synthesized with different methods are investigated by using multiple characterization techniques, including Raman scattering, optical absorption, and X‐ray absorption near edge structure, along with X‐ray photoemission by following the total valence bands and C 1s core‐level spectra. Four different SWNT materials (produced by arc discharge, HiPco, laser ablation, and CoMoCat methods) contain nanotubes with diameters ranging from 0.7 to 2.8 nm. The diameter distribution and the composition of metallic and semiconducting tubes of the SWNT materials are strongly affected by the synthesis method. Similar sp2 hybridization of carbon in the oxygenated SWNT structure can be found, but different surface functionalities are introduced while the tubes are processed. All the SWNTs demonstrate stronger plasmon resonance excitations and lower electron binding energy than graphite and multiwalled carbon nanotubes. These SWNT materials also exhibit different valence‐band X‐ray photoemission features, which are considerably affected by the nanotube diameter distribution and metallic/semiconducting composition.  相似文献   

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The reaction of NiCl2 and 3‐hydrazine‐4‐amino‐1,2,4‐triazole (Hatr) in the mixed solvent of EtOH and H2O yielded a dimer compound ([Ni2(Hatr)2(H2O)2(EtOH)2Cl2]Cl2·EtOH) with water and EtOH molecules coordinated to nickle ions. It crystallized in trigonal space group R‐3, a=b=29.67(1) Å, c=8.95(7) Å, β=120(1)°, as determined by single‐crystal X‐ray diffraction. Then, they were fully characterized by the IR spectroscopy, differential scanning calorimetry (DSC), thermogravimetry (TG), and elemental analysis.  相似文献   

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The six title compounds were prepared by annealing cold‐pressed pellets consisting of stoichiometric mixtures of binary rare earth and rhodium antimonides with additional elemental rhodium in evacuated silica tubes. Their crystal structure was determined from four‐circle X‐ray diffractometer data of a Eu6Rh30Sb19 single crystal, which was isolated from an arc‐melted sample annealed just below the melting temperature in a high‐frequency furnace. It is hexagonal: P63/m, a = 1693.2(2) pm, c = 408.11(4) pm, Z = 1. The least‐squares refinement resulted in a residual of R = 0.034 for 1259 structure factors and 62 variable parameters. The structure shows some disorder around the 63 axis but otherwise is very similar to the structures of Sc6Co30Si19 and Yb6Co30P19, but different from that of U6Co30Si19. The plot of the cell volumes of the new series Ln6Rh30Sb19 indicates the europium atoms in Eu6Rh30Sb19 to be at least partially divalent.  相似文献   

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《Chemphyschem》2002,3(12):1024-1030
N,N,N‐butylethylpentylpropylammonium iodide 4 and related molecules have been selectively synthesised from commercially available aldehydes, amines and alkyl iodides using a reductive alkylation procedure. The crystalline texture of 4 obtained on cooling is optically isotropic between crossed polarisers, indicating a cubic structure. Differential scanning calorimetry (DSC, +10 K min?1) reveals a glass phase transition at ?59 °C and a melting point at 192 °C. The melting entropy (23.9 J mol?1 K?1) indicates a first‐order transition between a highly disordered mesophase and the isotropic liquid. Powder X‐ray diffraction patterns were indexed in the cubic system (a=14.08Å; Pm n space group). In this cell, the molecular packing with Z=6 corresponds to a rather low compactness of 65 %. Iodine and tetraalkylammonium ions occupy positions with a m2 site symmetry. These highly symmetrical states may be generated by stepwise rotation of the ammonium cation. The same structural model for orientationally disordered crystal (ODIC) phases can be applied to a series of tetraalkylammonium bromides and iodides.  相似文献   

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A simple method is proposed for the electrodeposition of multilayers using a modified closed flow injection system. The apparatus incorporates flowing streams of electrolyte through a closed atmosphere flow cell for deposition of multilayers. Computer and software control is used to alternate the flow of electrolyte and control the alternating current or potential of the electrochemical cell. Electrodeposition of metallic multilayers of nickel/iron, iron/copper, cobalt/copper, and nickel/copper were used to test the instrument design. X‐ray diffraction was used to verify the composition and orientation of the films and scanning electron microscopy was used to examine the morphology of the deposited films. Advantages are discussed for using this type of instrumental setup for multilayer fabrication.  相似文献   

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