Anomalous dielectric behavior and thermal motion of water molecules confined in channels of porous coordination polymer crystals

Guest water molecules confined in channels of porous coordination polymer crystals [Ln(2)Cu(3)(IDA)(6)]·nH(2)O (Ln = La, Nd, Sm, Gd, Ho, Er; IDA = [NH(CH(2)COO)(2)](2-); n ≈ 9) exhibited large dielectric constants (ε) and antiferroelectric behaviors at high temperatures (e.g., ε(Sm) ≈ 1300 at 400 K). In addition, plots of the temperature dependence of ε showed broad peaks at ～170 K, below which ε became very small. These puzzling temperature dependences of ε are consistent with the results of molecular dynamics simulations, suggesting the "freezing of thermal motion" of water molecules at ～170 K.     

Confinement in carbon nanospace-induced production of KI nanocrystals of high-pressure phase

An outstanding compression function for materials preparation exhibited by nanospaces of single-walled carbon nanohorns (SWCNHs) was studied using the B1-to-B2 solid phase transition of KI crystals at 1.9 GPa. High-resolution transmission electron microscopy and synchrotron X-ray diffraction examinations provided evidence that KI nanocrystals doped in the nanotube spaces of SWCNHs at pressures below 0.1 MPa had the super-high-pressure B2 phase structure, which is induced at pressures above 1.9 GPa in bulk KI crystals. This finding of the supercompression function of the carbon nanotubular spaces can lead to the development of a new compression-free route to precious materials whose syntheses require the application of high pressure.     

Oxidation of Au by surface OH: nucleation and electronic structure of gold on hydroxylated MgO(001)

The nucleation and electronic structure of vapor-deposited Au on hydroxylated MgO(001) surfaces has been investigated under ultrahigh vacuum conditions. Hydroxylated MgO(001) surfaces with two different hydroxyl coverages, 0.4 and 1 monolayer, respectively, were prepared by exposure to water (D(2)O) at room temperature. Scanning tunneling microscopy experiments show significantly higher gold particle densities and smaller particle sizes on the hydroxylated MgO surface as compared to gold deposited on clean MgO(001). Infrared spectroscopy and X-ray photoelectron spectroscopy experiments were performed to reveal details about the initial nucleation of gold. Gold atoms are found to chemically interact with a specific type of hydroxyl groups on the MgO surface, leading to the formation of oxidized gold particles. The enhanced adhesion of Au particles, which is due to the formation of strong Au-O interfacial bonds, is responsible for the observed higher stability of small Au clusters toward thermal sintering on hydroxylated MgO surfaces. The results are compared to similar studies on Au/TiO(2)(110) model systems and powder samples prepared by the deposition-precipitation route.     

Field annealing effect on amorphous (FexCo1-x)85Nb15 alloys

The magnetic anisotropy induced by magnetic field annealing was examined for amorphous (Fe_xCo_1-x)₈₅Nb₁₅ alloys produced by a sputtering technique. An appreciably large uniaxial anisotropy was observed even at x = 0. The anisotropy constant (K_u) obtained was 2.3x10³ erg/cm³ at x=0, and it increased with x, showing a maximum of about 5.4x10³ erg/cm³ near x = 0.2. This compositional change in K_u was explained in terms of the directional ordering of magnetic Fe-Co atom pairs under the negative nonmagnetic interaction energy leading to a precipitation.     

Complexation and rate of polymerization of acrylic acid and methacrylic acid in the presence of poly(4-vinylpyridine) in dilute methanol solution

A 1:1 hydrogen-bonded complex was formed between acrylic acid (AA) or methacrylic acid (MA) and the pyridine group of poly(4-vinylpyridine) (P4VP) in dilute solutions. A shift of infrared absorption of the hydrogen-bonded acid O? H to a lower energy direction and an upfield shift of acid proton in the NMR were observed when the monomers were added with pyridine. The equilibrium constants of the 1:1 complexation with P4VP measured by using a semipermeable membrane were 0.58 and 0.26 for AA and MA, respectively, at 25°C in methanol. The bromometrically measured initial rate of radical polymerization showed only a slight enhancement in the presence of P4VP, the rate being maximum at the 4VP unit:monomer mole ratio of 0.25 and 0.5 for AA and MA, respectively, in dilute methanol solution at 60°C.     

Virtual miscibility gap and interdiffusion coefficient in iron-nickel invar alloys

Fe-Ni Invar alloys exhibit anomalies in thermodynamic and physical properties at high temperatures. This is considered to result from the tendency to two-phase separation in the fcc phase. This idea is supported also by interdiffusion experiments in the Fe-Ni system, where the interdiffusion coefficient is anomalously small in the Invar region at lower temperatures. A simple theory of regular solutions based on a pair interaction model is applied to the Fe-Ni system; with the assumption of two gamma states this gives a miscibility gap in the Invar region.     

Micro-emulsion synthesis of monodisperse surface stabilized silicon nanocrystals

Silicon nanocrystals with a uniform size distribution were synthesized in inverse micelles using powerful hydride reducing agents. The silicon nanocrystals surfaces were then stabilized with 1-heptene to produce particles with strong blue photoluminescence.     

Electronic structure of TiH2

The electronic structure of TiH₂ has been studied using the augmented-plane-wave method and the LCAO interpolation. The density of states and its orbital components show that the conduction band is Ti d-like and that the valence band is largely derived from the hydrogen orbitals with small Ti 3d hybridization. The electronic charges on the hydrogen atom are ～ 1.5 as compared to 1.6–1.7 of the rare-earth metal hydrides.     

Iodine catalyzed reduction of arenesulfonic acid to the arenethiol with triphenylphosphine

Arenesulfonic acids, its sodium salts, and alkyl arenesulfonates were reduced readily to the corresponding arenethiols quantitatively with triphenylphosphine in the presence of iodine.