Direct observation of polymer-stabilized blue phase I structure with confocal laser scanning microscope

The three-dimensional structure of polymer-stabilized blue phase with the order of optical wavelength was nondestructively investigated by a confocal laser scanning microscope. The periodical patterns corresponding to the bcc lattice were observed not only on the surface but also in the internal region. The visualization mechanism was expected to be back scattering caused by liquid crystal order.     

Two‐component molecular crystals from N‐heteroaromatics and nitro­benzoic acids

Five two‐component molecular crystals, benzimidazolium 3‐nitro­benzoate, C₇H₇N₂⁺·C₇H₄NO₄^?, (I), benzimidazolium 4‐nitro­benzoate, C₇H₇N₂⁺·C₇H₄NO₄^?, (II), 1H‐benzotriazole–3‐nitro­benzoic acid (1/1), C₆H₅N₃·C₇H₅NO₄, (III), imidazol­ium 3‐nitro­benzoate, C₃H₅N₂⁺·C₇H₄NO₄^?, (IV), and imid­azolium 4‐nitro­benzoate, C₃H₅N₂⁺·C₇H₄NO₄^?, (V), were prepared with the aim of making chiral crystals. Only (I) crystallizes in a chiral space group. The mol­ecules of (I) and (II) are linked by hydrogen bonds to form 2₁ spiral chains. In (III), (IV) and (V), macrocyclic structures are formed from two acid and two base components, by an alternate arrangement of the acid and base moieties.     

All-solid-state high-peak-power Ti:sapphire laser system above 5-kHz repetition rate

We have developed an all-solid-state Ti:sapphire laser system, which produces 22-fs, 0.2-TW pulses at 5-kHz repetition rate. An average power of 22.2 W is the highest ever obtained in ultrashort laser sources. The serious thermal lensing due to high power pumping in a small area of Ti:sapphire crystal is controlled successfully by a stable quasi-cavity with two concave mirrors. The attempt to increase the repetition rate to 10 kHz is also described.     

Reactivity of a phosphoranyl radical generated by photoreaction of phenyl diphenylphosphinite with 10-methylacridinium iodide. α-Scission vs. single electron transfer

Photoreaction of phenyl diphenylphosphinite ( 1b ) with 10-methylacridinium iodide ( 2 ) in aqueous acetonitrile under an argon atmosphere gives 10-methylacridan, the reduction product from 2 , in a quantitative yield and phenyl diphenylphosphinate, the oxidation product from 1b , in a low yield, as well as a large amount of diphenylphosphinic acid and a moderate amount of phenol. The product distribution observed here is interpreted well in terms of decomposition of a phosphoranyl intermediate through both α-scission and single electron transfer (SET) pathways.     

Diffraction study of Li2O·SiO2 glass with computer simulation

The structure of Li₂O·SiO₂ glass has been determined by the pair-function analysis of the radial distribution function (RDF) obtained by X-ray and neutron diffraction measurements. The structure models were constructed by the molecular dynamics method (MD). The calculated RDFs, the summation of the pair-functions of the model, were compared with the observed RDFs while varying the MD parameters. Taking advantage of the negative scattering length of Li for neutron diffraction, the glass structure was investigated in detail, and it was found that the chains of SiO₄ tetrahedra bend at 20 °, which is a little less than for the crystal (23.48 °). It is known that the larger the size of the alkali ions (Na⁺ → K⁺ → Cs⁺), the smaller the bending angle of the chains. It was found that this rule also applies to Li⁺.     

Palladium-Catalyzed [3+2] and [2+2+2] Annulations of 4-Iodo-2-quinolones with Activated Alkynes through Selective C−H Activation

The palladium-catalyzed reaction of 4-iodo-2-quinolones with activated alkynes was investigated. Cyclopenta[de]quinoline-2(1 H)-ones and/or phenanthridine-6(5 H)-ones were obtained through [3+2] annulation involving aromatic C−H activation or [2+2+2] annulation involving vinylic C−H activation, respectively. Reasonable mechanisms for the formation of these annulation products have been proposed based on density functional theory calculations.     

Relationship between magnetic structure and ferroelectricity of systems with CuO2 ribbon chains

Results of experimental studies carried out by various methods on systems with CuO₂ ribbon chains are presented. For LiVCuO₄, which was found to have helimagnetic and ferroelectric simultaneous transitions (multiferroic transitions), the relationship between the magnetic structure and the ferroelectricity is described in detail by showing their magnetic field dependences. For Li₂ZrCuO₄, NMR studies have revealed that the system has ac-helical magnetic structure. However, we have not observed the ferroelectricity in this ordered phase. This result suggests that there may exist the antiferro-type ordering, for example, of the helical axis vectors, of the CuO₂ chains. Several new findings are also shown on the magnetic and dielectric properties of other ribbon chain systems, LiVCuO₄, Li₂ZrCuO₄, LiCu₂O₂ and NaCu₂O₂ and a related system Na₂Cu₃(GeO₃)₄.     

Kinetics of ion transfer at the ionic liquid/water nanointerface

Ion transfer (IT) processes in ionic liquids (ILs) are essential for their applications in electrochemical systems and chemical separations. In this Article, the first measurements of IT kinetics at the IL/water interface are reported. Steady-state voltammetry was performed at the nanometer-sized polarizable interface between water and ionic liquid, [THTDP(+)][C(4)C(4)N(-)], immiscible with it that was formed at the tip of a nanopipet. Kinetic measurements at such interfaces are extremely challenging because of slow mass-transfer rates in IL, which is ～700 times more viscous than water. The recently developed new mode of nanopipet voltammetry, common ion voltammetry, was used to overcome technical difficulties and ensure the reliability of the extracted kinetic parameters of IT. The results suggest that the rate of interfacial IT depends strongly on solution viscosity. Voltammetric responses of nanopipets of different radii were analyzed to evaluate the effect of the electrical double layer at the liquid/liquid interface on IT kinetics. The possibility of the influence of the charged pipet wall on ion transport was investigated by comparing currents produced by cationic and anionic species. Possible effects of relaxation phenomena at the IL/water interface on IT voltammograms have also been explored.     

Numerical simulations of acoustic cavitation noise with the temporal fluctuation in the number of bubbles

Numerical simulations of cavitation noise have been performed under the experimental conditions reported by Ashokkumar et al. (2007) [26]. The results of numerical simulations have indicated that the temporal fluctuation in the number of bubbles results in the broad-band noise. “Transient” cavitation bubbles, which disintegrate into daughter bubbles mostly in a few acoustic cycles, generate the broad-band noise as their short lifetimes cause the temporal fluctuation in the number of bubbles. Not only active bubbles in light emission (sonoluminescence) and chemical reactions but also inactive bubbles generate the broad-band noise. On the other hand, “stable” cavitation bubbles do not generate the broad-band noise. The weaker broad-band noise from a low-concentration surfactant solution compared to that from pure water observed experimentally by Ashokkumar et al. is caused by the fact that most bubbles are shape stable in a low-concentration surfactant solution due to the smaller ambient radii than those in pure water. For a relatively high number density of bubbles, the bubble–bubble interaction intensifies the broad-band noise. Harmonics in cavitation noise are generated by both “stable” and “transient” cavitation bubbles which pulsate nonlinearly with the period of ultrasound.     

Dependence of sonochemical parameters on the platinization of rutile titania – An observation of a pronounced increase in photocatalytic efficiencies

Using a standing wave sonochemical reactor (SWSR), the influences of parameters of ultrasonic power input, sonication time, sonication temperature and the amount of propanol (which generates the reducing radicals) were systemically investigated to ascertain and optimize the best conditions for the sonochemical reduction of Pt from its precursor hexachloroplatinic acid and then its deposition on rutile TiO₂ (platinization of rutile titania) catalysts. Catalytic activity of the prepared platinized catalysts was tested in the reaction of methyl orange degradation. The results of photocatalytic activity study in the degradation of methyl orange further demonstrate that sonochemically as-prepared Pt/TiO₂ catalysts show a pronounced increase (～2 times) in photodegradation, even with a deposition of small amounts of platinum (1.4 wt.%), as compared to the unsupported or naked rutile titania. Although there are various parameters that influence the sonochemical platinization of rutile titania, the present optimization results clearly indicate that the best photocatalytic degradation of methyl orange can be obtained when the experimental conditions of the preparation were with an input power of 50 W, an initial hexachloroplatinic acid volume of 70 ml (which results into 1.4 wt.% Pt on TiO₂), sonication time of 90 min, 0.18 g of propanol and a temperature of 10 °C were adopted. The method of ultrasound application to prepare metal supported semiconductors has many advantages such as convenience, safety and high efficiency. Furthermore, it is hopeful that this optimization study can also be extended to the generation of similar metal supported semiconductors.