Aromatic Ring‐Fused Carborane‐Based Luminescent π‐Conjugated Polymers

A series of π‐conjugated polymers linked by benzocarborane (1,2‐(buta‐1′,3′‐diene‐1′,4′‐diyl)‐1,2‐dicarbadodecaborane) were synthesized via Sonogashira–Hagihara polycondensation reaction. The opened molecular structure of diiodo monomer containing benzocarborane resulted in fast polymerization and high molecular weights. The obtained polymers were fully characterized by ¹H, ¹³C, and ¹¹B NMR spectroscopies. UV‐vis absorption and photoluminescence studies revealed the acceptor‐profile of benzocarborane. Unlike the polymers linked by o‐carborane, these polymers exhibited strong luminescence in the solution state, presumably because the inductive effect of carborane is dominant, rather than cage‐π interactions.

     

Target structure induced suppression of the ionization cross section for very low energy antiproton-hydrogen collisions

Low energy antiprotons have been used previously to give benchmark data for theories of atomic collisions. Here we present measurements of the cross section for single, nondissociative ionization of molecular hydrogen for impact of antiprotons with kinetic energies in the range 2-11 keV, i.e., in the velocity interval of 0.3-0.65 a.u. We find a cross section which is proportional to the projectile velocity, which is quite unlike the behavior of corresponding atomic cross sections, and which has never previously been observed experimentally.     

Synthesis of cold antihydrogen in a cusp trap

We report here the first successful synthesis of cold antihydrogen atoms employing a cusp trap, which consists of a superconducting anti-Helmholtz coil and a stack of multiple ring electrodes. This success opens a new path to make a stringent test of the CPT symmetry via high precision microwave spectroscopy of ground-state hyperfine transitions of antihydrogen atoms.     

An alternative to inflation? Critical role of neutrino anisotropic stress in CMB

We study the role of anisotropic stress in the evolution of curvature perturbations and the cosmic microwave background (CMB) power spectrum. We found that if the extra anisotropic stress preexisted before the neutrino decoupling, the cancellation of the anisotropic stress of neutrinos and extra anisotropic stress could lead to a spectrum that could reproduce the observed CMB power spectrum.     

Regiospecific synthesis of 2‐substituted furanonaphthoquinones

The naturally‐occurring furanonaphthoquinones 1a‐d have been synthesized from 3‐furancarboxylic acid and 2,3‐dimethoxybenzaldehyde via the Birch reduction‐elimination.     

Structural- and chemical-phase-separation on single crystalline sapphire (0001) surfaces

Atomic force microscopy (AFM) was used to characterize morphology and chemistry on step-controlled single crystalline sapphire (0001) surfaces. Hydrophilicity on the surface can be evaluated using frictional force imaging. A sapphire surface that is covered with bunched steps accompanied with crossing steps clearly exhibits the phase-separation into two domains with different hydrophilicity, where an almost hydrophobic domain forms inside a hydrophilic area. By analyzing the histogram of the step height, we concluded that the difference in the hydrophilicity is associated with the surface reconstruction. We found that the phase-separation characterized by the hydrophilicity and charge potential self-organizes on the sapphire surface with specific step arrangements. We demonstrated selective adsorption of biomolecules on step-controlled surfaces as an example of the application.     

Synthesis of ZnO nanoparticles using nanosecond pulsed laser ablation in aqueous media and their self-assembly towards spindle-like ZnO aggregates

ZnO nanoparticles were fabricated by pulsed laser ablation (PLA) of a Zn metal in aqueous media, and aging effects on the morphology and photoluminescence properties of ZnO nanoparticles were investigated. The crystalline phase and particle morphology were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It was found that small, well-defined ZnO nanoparticles were obtained by PLA of a Zn plate in aqueous media, and subsequent aging of the obtained ZnO nanoparticle suspension produced in cetyltrimethylammonium bromide (CTAB) solution led to the formation of spindle-like ZnO aggregates. However, in deionized water not the spindle-like ZnO aggregates but fluffy round aggregates were obtained. High-resolution transmission electron microscopic (HRTEM) observation indicated that the spindle-like ZnO aggregates were composed of many well-defined nanoparticles. Spindle-like aggregates exhibited strong exciton emission, while green emission could be suppressed via an aging process in the presence of CTAB. Moreover, thin films prepared by electrophoretic deposition (EPD) of ZnO nanoparticles after PLA in the presence of CTAB also possessed highly elongated aggregate structures that were possibly formed by surrounding the ZnO nanoparticles with double layers of CTAB molecules.     

Synthesis and properties of poly(carbonate‐urethane) consisting of alternating carbonate and urethane moieties

Poly(carbonate‐urethane) consisting of alternating carbonate and urethane moieties (poly(HC‐MDI)) was prepared by polyaddition of 4,4′‐diphenylmethane diisocyanate (MDI) and a monocarbonate diol bis(3‐hydroxypropyl)carbonate (HC), prepared by hydrolysis of a six‐membered spiroorthocarbonate 1,5,7,11‐tetraoxa‐spiro[5.5]undecane. The polyaddition proceeds without concomitant side reactions including carbonate exchange reaction and affords the desired poly(carbonate‐urethane). The hydrolysis and thermal behaviors of poly(HC‐MDI) were compared with those of the analogous polyurethane carrying no carbonate structure (poly(ND‐MDI)) prepared from MDI and 1,9‐nonanediol (ND). Although the glass transition behaviors are almost identical, poly(HC‐MDI) is less crystalline than poly(ND‐MDI). Poly(HC‐MDI) is more susceptible to hydrolysis than poly(ND‐MDI) probably due to the higher polarity and the lower crystallinity. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2802–2808, 2006     

Effect of oxidation dynamics on the film characteristics of Ce:YIG thin films deposited by pulsed-laser deposition

Thin films with different compositions of Ce-substituted yttrium iron garnet (Ce:YIG (Y₂CeFe₅O₁₂)), Ga-doped Ce:YIG (Ce:Ga:YIG (Y₂CeFe_4.25Ga_0.75O₁₂)), and Gd-doped Ce:YIG (Ce:Gd:YIG (Y_1.6CeGd_0.4Fe₅O₁₂)) were deposited on gadolinium gallium garnet (GGG (Gd₃Ga₅O₁₂)) substrates in O₂ or Ar background gas by pulsed-laser deposition (PLD) technique. Crystalline films were obtained at a lower O₂ gas pressure of 20 mTorr or at higher Ar gas pressures of more than 100 mTorr. In addition, the behavior of YO molecules was visualized by two-dimensional laser-induced fluorescence (2D-LIF), in order to investigate the oxidation dynamics in the ablation plume. The oxidation dynamics and the crystallinity had close correlation.     

Multi-reflection time-of-flight mass spectrograph for short-lived radioactive ions

RIKEN’s new RI-Beam Factory (RIBF) will provide unprecedented access to neutron-rich nuclei of importance to r-process nucleosynthesis. We are constructing an advanced multi-reflection time-of-flight mass spectrograph to perform precision mass measurements of these nuclei. We discuss the device and compare its performance to that of the well-known Penning trap mass spectrometer.