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51.
Seo K Kim C Choi YS Park KA Lee YH Kim B 《Journal of the American Chemical Society》2003,125(46):13946-13947
CO2 molecule chemisorbs selectively on the zigzag tube edge without an activation barrier, whereas it physisorbs on the armchair edge of nanotubes. In addition, carbon nanotubes can be etched by an adsorbed oxygen atom of CO2 molecule. From our results, we suggest a selective etching mechanism for tuning the chirality of the mass-produced carbon nanotubes. 相似文献
52.
Noveron JC Lah MS Del Sesto RE Arif AM Miller JS Stang PJ 《Journal of the American Chemical Society》2002,124(23):6613-6625
We report the supramolecular chemistry of several metal complexes of N-(4-pyridyl)benzamide (NPBA) with the general formula [Ma(NPBA)2AbSc], where M = Co2+, Ni2+, Zn2+, Mn2+, Cu2+, Ag+; A = NO3-, OAc-; S = MeOH, H2O; a = 0, 1, 2; b = 0, 1, 2, 4; and c = 0, 2. NPBA contains structural features that can engage in three modes of intermolecular interactions: (1) metal-ligand coordination, (2) hydrogen bonding, and (3) pi-pi stacking. NPBA forms one-dimensional (1-D) chains governed by hydrogen bonding, but when reacted with metal ions, it generates a wide variety of supramolecular scaffolds that control the arrangement of periodic nanostructures and form 1- (2-4), 2- (5), or 3-D (6-10) solid-state networks of hydrogen bonding and pi-pi stacking interactions in the crystal. Isostructural 7-9 exhibit a 2-D hydrogen bonding network that promotes topotaxial growth of single crystals of their isostructural family and generates crystal composites with two (11) and three (12) different components. Furthermore, 7-9 can also form crystalline solid solutions (M,M')(NPBA)2(NO3)2(MeOH)2 (M, M' = Co2+, Ni2+, or Zn2+, 13-16), where mixtures of Co2+, Ni2+, and Zn2+ share the same crystal lattice in different proportions to allow the formation of materials with modulated magnetic moments. Finally, we report the effects that multidimensional noncovalent networks exert on the magnetic moments between 2 and 300 K of 1-D (4), 2-D (5), and 3-D (7, 8, 10, and 13-16) paramagnetic networks. 相似文献
53.
1-(p-Substituted phenyl)-2-vinylcyclopropanes such as 1-phenyl-2-vinylcyclopropane (Ia), 1-(p-chlorophenyl)-2-vinylcyclopropane (Ib), 1-(p-anisyl)-2-vinylcyclopropane (Ic), and 1-(p-tolyl)-2-vinylcyclopropane (Id) were prepared and polymerized radically, cationically and with Ziegler–Natta catalysts. Ia and Ib polymerized exclusively in 1,5-fashion with radical initiators. However, Ic and Id polymerized in 1,5-fashion only with Ziegler–Natta catalysts. All polymers were soluble in ordinary organic solvent and solution-cast films were clear and flexible, showing Tg values in the range of 39–71°C. Spectral data indicated that the double bonds of the polymer chains were in trans form in all cases. The difference between the polymerizabilities of different monomers are interpreted in terms of electronic properties of substituents. 相似文献
54.
The effect of terminal groups of oligomer electrolytes on the photovoltaic performance of dye-sensitized solar cells (DSSCs) have been systematically investigated to show that the terminal group plays a critical role in determining the concentration of I(3)(-), ionic conductivity, flatband potential and consequently the energy conversion efficiency. 相似文献
55.
Molecular reorientation in the presence of internal rotation is investigated and an analytical expression for the spin—rotational rate of a nucleus attached to the internal rotor is obtained in terms of the internal angular-momentum correlation time. A model of a symmetric-top molecule undergoing anisotropic rotational diffusion is extended to include a modified extended diffusion of internal rotation. The result is applied to liquid toluene and the internal angular-momentum correlation time is evaluated from the 13C nuclear spin—rotational relaxation rate of the methyl carbon. A comparison with the previous result on the dipole—dipole relaxation data is made and the consistency of the present theory is discussed. 相似文献
56.
Anantha Iyengar Gopalan Kwang-Pill Lee Kalayil Manian Manesh Jun Heon Kim Jae Soo Kang 《Talanta》2007,71(4):1774-1781
A modified electrode is fabricated by embedding gold nanoparticles into a layer of electroactive polymer, poly(4-aminothiophenol) (PAT) on the surface of glassy carbon (GC) electrode. Cyclic voltammetry (CV) is performed to deposit PAT and concomitantly deposit Au nanoparticles. Field emission transmission electron microscopic image of the modified electrode, PAT-Aunano-ME, indicates the presence of uniformly distributed Au nanoparticles having the sizes of 8-10 nm. Electrochemical behavior of the PAT-Aunano-ME towards detection of ascorbic acid (AA) and dopamine (DA) is studied using CV. Electrocatalytic determination of DA in the presence of fixed concentration of AA and vice versa, are studied using differential pulse voltammetry (DPV). PAT-Aunano-ME exhibits two well defined anodic peaks at the potential of 75 and 400 mV for the oxidation of AA and DA, respectively with a potential difference of 325 mV. Further, the simultaneous determination of AA and DA is studied by varying the concentration of AA and DA. PAT-Aunano-ME exhibits selectivity and sensitivity for the simultaneous determination of AA and DA without fouling by the oxidation products of AA or DA. PAT and Au nanoparticles provide synergic influence on the accurate electrochemical determination of AA or DA from a mixture having any one of the component (AA or DA) in excess. The practical analytical utilities of the PAT-Aunano-ME are demonstrated by the determination of DA and AA in dopamine hydrochloride injection and human blood serum samples. 相似文献
57.
Park S Kwon OH Kim S Park S Choi MG Cha M Park SY Jang DJ 《Journal of the American Chemical Society》2005,127(28):10070-10074
We have synthesized a novel class of imidazole-based excited-state intramolecular proton-transfer (ESIPT) materials, i.e., hydroxy-substituted tetraphenylimidazole (HPI) and its derivative HPI-Ac, which formed large single crystals exhibiting intense blue fluorescence and amplified spontaneous emission (ASE). Transparent, clear, and well-defined fluorescent single crystals of HPI-Ac as large as 20 mm x 25 mm x 5 mm were easily grown from its dilute solution. From the X-ray crystallographic analysis and semiempirical molecular orbital calculation, it was deduced that the four phenyl groups substituted into the imidazole ring of HPI and HPI-Ac allowed the crystals free from concentration quenching of fluorescence by limiting the excessive tight-stacking responsible for intermolecular vibrational coupling and relevant nonradiative relaxation. Fluorescence spectral narrowing and efficient ASE were observed in the HPI-Ac single crystal even at low excitation levels attributed to the intrinsic four-level ESIPT photocycle. 相似文献
58.
Won Young Jung Byung Ho Noh Seung Hee Baek Gun-Dae Lee Seong Soo Park Seong-Soo Hong 《Reaction Kinetics and Catalysis Letters》2007,91(2):223-231
SBA-15 mesoporous material was prepared by microwave-hydrothermal method and was used as support in TiO2-loaded SBA-15 photocatalysts. The physical properties of these particles were investigated. We also examined the activity
of these samples as photocatalysts for the decomposition of orange II. Titania loaded on a silica matrix decreases the surface
area of the support as expected for TiO2 incorporation. For TiO2-loaded SBA-15 photocatalysts, the IR absorption at ∼960 cm−1 commonly accepted as the characteristic vibration of the Ti-O-Si bond. The photocatalytic activity increases with an increase
of the TiO2 loading. 相似文献
59.
Remarkable separation performance of olefin/paraffin mixtures was previously reported by facilitated olefin transport through silver-based polymer electrolyte membranes. The mechanism of facilitated olefin transport in solid membranes of AgCF3SO3 dissolved in poly(N-vinyl pyrrolidone) (PVP) is investigated. In silver polymer electrolyte membranes, only free anions are present up to the 2:1 mole ratio of [C=O]:[Ag], and ion pairs start to form at a ratio of 1:1, followed by higher-order ionic aggregates above a ratio of 1:2. At silver concentrations above 3:1, the propylene permeance increases almost linearly with the total silver concentration, unexpectedly, regardless of the silver ionic constituents. It was also found that all the silver constituents, including ion pairs and higher order ionic aggregates, were completely redissolved into free anions under the propylene environment; this suggests that propylene can be a good ligand for the silver cation. From these experimental findings, a new mechanism for the complexation reaction between propylenes and silver salts in silver-polymer electrolytes was proposed. The new mechanism is consistent with the linearity between the propylene permeance and the total silver concentration regardless of the kind of the silver constituents. Therefore, the facilitated propylene transport through silver-polymer electrolytes may be associated mainly with the silver cation weakly coordinated with both carbonyl oxygen atoms and propylene. 相似文献
60.