2H NMR study of phase transition and hydrogen dynamics in hydrogen bonded organic antiferroelectric 55DMBP-H2ca

Hydrogen dynamics in one-dimensional hydrogen bonded organic antiferroelectric, co-crystal of 5,5’-dimethyl-2,2’-bipyridine (55DMBP) and chloranilic acid (H₂ca), was investigated by use of ²H high resolution solid-state NMR. The two types of hydrogen bonds O-H …N and N⁺-H …O^? in the antiferroelectric phase were clearly observed as the splitting of the side band of the ²H MAS NMR spectra of the acid-proton deuterated compound 55DMBP-D ₂ca. The temperature dependence of the spin-lattice relaxation time was measured of the N⁺-H and O-H deuterons, respectively. It was suggested that the motion of the O-H deuteron is already in the antiferroelectric phase in the fast-motion regime in the NMR time scale, while that of the N⁺-H deuteron is a slow motion. In the high-temperature paraelectric phase, the both deuterons become equivalent and the fast motion of the deuterons in the NMR time scale is taking place with the activation energy of 7.9 kJ mol^?1.     

Magnetic anisotropy of amorphous (Fe1−x Co x )78Si10B12 alloys

In order to better understand the problem of magnetic anisotropy in amorphous alloys produced by a rapidly quenching technique, in-plane magnetic anisotropy of amorphous (Fe_1−x Co _x (₇₈Si₁₀B₁₂ alloys was measured by means of a torque magnetometer using a disk specimen made from the amorphous alloy ribbon. The amorphous ribbons were prepared by a single roller type quenching apparatus. It was found that the anisotropy had mostly twofold symmetry in all the alloy cases, and that the concentrationx dependence of the anisotropy constant behaved differently from that of the magnetostriction. Moreover, the anisotropy did not disappear by subsequent annealing at high temperatures where the internal stress relief and the crystallization were completed.     

Direct observation of the mass renormalization in SrVO3 by angle resolved photoemission spectroscopy

Band dispersions and Fermi surfaces of the three-dimensional Mott-Hubbard system SrVO3 are directly observed by angle-resolved photoemission spectroscopy. An observed spectral weight distribution near the Fermi level (E(F)) shows cylindrical Fermi surfaces as predicted by band-structure calculations. By comparing the experimental results with calculated surface electronic structures, we conclude that the obtained band dispersion reflects the bulk electronic structure. The enhanced effective electron mass obtained from the energy band near E(F) is consistent with the bulk thermodynamic properties and hence with the normal Fermi-liquid behavior of SrVO3.     

Tropolone as a High‐Performance Robust Anchoring Group for Dye‐Sensitized Solar Cells

A tropolone group has been employed for the first time as an anchoring group for dye‐sensitized solar cells (DSSCs). The DSSC based on a porphyrin, YD2‐o‐C8T, with a tropolone moiety exhibited a power‐conversion efficiency of 7.7 %, which is only slightly lower than that observed for a reference porphyrin, YD2‐o‐C8 , with a conventional carboxylic group. More importantly, YD2‐o‐C8T was found to be superior to YD2‐o‐C8 with respect to DSSC durability and binding ability to TiO₂. These results unambiguously demonstrate that tropolone is a highly promising dye‐anchoring group for DSSCs in terms of device durability as well as photovoltaic performance.     

Time-resolved Fourier transform infrared emission spectroscopy of laser ablation products

Time-resolved Fourier transform infrared spectroscopy was applied for observations of emission spectra from ablation products induced by a Nd:YLF laser with a 2.5 kHz repletion rate. The infrared emission spectra from Fe, Cu, Zn, and Al atoms were observed in the 2.5–5 μm region. The observed emission spectrum from iron ablation in the 2500 cm⁻¹ region agrees very well with solar absorption spectrum, where new lines have been detected in the present experiment in addition to the lines observed from a hollow cathode discharge. When O₂ was added to the carbon ablation, emissions from vibrationally excited CO were observed with non-equilibrium vibrational distribution.     

Factors affecting the loading efficiency of water-soluble drugs in PLGA microspheres

Poly(lactide-co-glycolide), PLGA, microspheres containing blue dextran as a hydrophilic model drug were prepared by a solvent evaporation method from w/o/w emulsions using a micro homogenizer. Effects of surfactant concentration in oil phase, stirring time period and stirring rate in the preparation procedure of primary emulsion (w/o) upon drug-loading efficiency were evaluated. Stirring rate during preparation of primary emulsion and surfactant concentration in oil phase affected drug-loading efficiency and the particle size of primary emulsion. Microspheres having the higher drug-loading efficiency were obtained when size differences between the primary emulsions and the secondary ones were large. That is, when the diameter of the primary emulsion is much smaller than that of the secondary emulsion, PLGA microspheres with high-loading efficiency of blue dextran were obtained.     

Effect of polyethylene glycol on preparation of rifampicin-loaded PLGA microspheres with membrane emulsification technique

Monodisperse poly(lactide-co-glycolide) (PLGA) microspheres containing rifampicin (RFP), anti-tubercle drug, as hydrophobic model drug were prepared by solvent evaporation method with a membrane emulsification technique using Shirasu Porous Glass (SPG) membranes. Five kinds of rifampicin-loaded PLGA (RFP/PLGA) microspheres with different sizes were prepared by changing pore size of the membranes. Effect of polyethylene glycol (PEG) added to polyvinyl alcohol (PVA) solution (continuous phase) upon the monodispersity of microspheres was studied. PEG was used as a stabilizer for microspheres dispersing in PVA solution. The most suitable molecular weight of PEG as a stabilizer was 20,000. RFP/PLGA microspheres prepared with PEG20000 were apparently more uniform than those prepared without PEG. The yield of RFP/PLGA microspheres was 100%. The initial burst observed in the release of RFP from RFP/PLGA microspheres was suppressed by the addition of PEG.     

Anomaly of CH4 molecular assembly confined in single-wall carbon nanohorn spaces

Vibrational-rotational properties of CH(4) adsorbed on the nanopores of single-wall carbon nanohorns (SWCNHs) at 105-140 K were investigated using IR spectroscopy. The difference vibrational-rotational bands of the ν(3) and ν(4) modes below 130 K show suppression of the P and R branches, while the Q branches remain. The widths of the Q branches are much narrower than in the bulk gas phase due to suppression of the Doppler effect. These results indicate that the rotation of CH(4) confined in the nanospaces of SWCNHs is highly restricted, resulting in a rigid assembly structure, which is an anomaly in contrast to that in the bulk liquid phase.     

Structure and mechanical properties in drawn poly(l‐lactide)/clay hybrid films

Films composed of poly(l ‐lactide) (PLLA)/organophilic montmorillonite hybrids (PLACHs) have been prepared via a melt‐compounding process, which is followed by uniaxial drawing at 90°C in air. In addition, an enhancement of the mechanical properties of these drawn PLACH films, which is expected to differ depending on the drawn ratios, is also estimated by dynamic viscoelastic measurements. Three different organoclay concentrations in the hybrid of 3, 5, and 9 wt% were investigated. The structural parameters for the PLLA crystallites in the drawn films, such as the c‐axis orientation function (f_PLLA) and crystallite size, were measured by X‐ray diffraction, and their drawn ratio (λ) and clay concentration dependence were examined from a textural viewpoint. Another orientation function (f_clay) of the organoclay particles was obtained by transmission electron microscopy (TEM). The values of f_PLLA and crystallinity for PLLA sharply increased with λ for λ < 3, although f_clay was unchanged during the initial stage of elongation. In the high‐λ region (>5), the organoclay particles in the PLACHs started orienting themselves parallel to the draw direction. Copyright © 2008 John Wiley & Sons, Ltd.