Control over Internal Structure of Liquid Crystal Polymer Nanofibers by Electrospinning

Liquid crystal polymer nanofibers with a diameter ranging from 0.13 to 4.71 µm were prepared by electrospinning from a main‐chain liquid crystalline polyester, BB‐5(3‐Me). WAXD measurements showed that the formation and orientation of the ordered structure in the electrospun fibers were controlled by the fiber diameter formed during electrospinning. For BB‐5(3‐Me), the SmA structure with two layer spacings was formed in the fiber during the electrospinning. Under optimal spinning conditions, the SmA structure is highly oriented in the fiber. In addition, annealing transformed the metastable SmA structure in the BB‐5(3‐Me) fiber into stable SmCA one.

     

Flow waves of hierarchical pattern formation induced by chemical waves: The birth, growth and death of hydrodynamic structures

We introduce a short review of chemically driven convection together with a series of our experiments on hydrodynamic instabilities induced by chemical waves excited in the batch reactor of a Belousov-Zhabotinsky reaction. Several unresolved phenomena are picked out and possible mechanisms are discussed extensively. Interesting features of these phenomena can be summarized as being caused by the ‘global and dynamic hydrodynamic pattern induced by chemical waves’. These chemically induced global pattern of hydrodynamic phenomena may not be simply explained by the reaction-diffusion-convection model based on Marangoni instability (surface tension-driven convection), which produces only a localized structure of the convection pattern. Observed flow waves show global and dynamic patterns of convection that generate a functional structure associated with hierarchical patterns appearing in the reaction-diffusion-convection system. In particular, we clarify the existence of a continuous stream of hydrodynamic flow with growing amplitude and its rotating direction. We find that the flow does not stabilize to a motionless state until the system has self-collapsed. This new picture of the flow waves requires a revision of the reaction-diffusion-convection model. The established flow structure can be regarded as a mixing and/or transport process to supply the substrate from the peripheral region to the centre of the chemical waves to sustain the reaction. This characteristic may be a function of the hierarchical structure. A new mechanism for the viscous-elastic feature of the gas-liquid interface is discussed in order to understand these curious phenomena of interest.     

Space-selective phase separation inside a glass by controlling compositional distribution with femtosecond-laser irradiation

Space-selective phase separation was induced inside Na₂O–SiO₂ glasses by changing the glass composition locally from a miscible composition to an immiscible one via femtosecond-laser irradiation at a high repetition rate. The formation of a nanoscale co-continuous structure due to phase separation was confirmed by scanning electron microscopy after heat treatment, polishing until the laser-modified area was exposed, and subsequent etching. The configuration of the structure could be controlled by changing the heat-treatment time.     

Effect of ion-exchange nanofiber fabrics on water splitting in bipolar membrane

In the present study, the effect of ion-exchange fiber fabric made by electrospray deposition (ESD) on water splitting in a composite bipolar membrane (CBM) was investigated. Cation- and anion-exchange fiber (CEF and AEF) fabrics, which were composed of very thin fibers, were prepared by ESD and postdeposition chemical modification and then used as the intermediate layer of a CBM. The current-voltage characteristics under reverse bias conditions showed that the AEF fabrics enhanced water splitting. The water dissociation is accelerated by the AEF fabric, which contains both tertiary pyridyl groups and quaternary pyridinium groups and has a high specific surface area. On the other hand, the CEF fabric, which contains sulfonic acid groups and has an insufficient specific surface area, reduced water splitting. These results indicate that fiber fabric with catalytic activity and a high surface area obtained by ESD can improve the performance of a CBM.     

AlN bulk single crystal growth on 6H-SiC substrates by sublimation method

Large and thick AlN bulk single crystals up to 43 mm in diameter and 10 mm in thickness have been successfully grown on 6H-SiC (0 0 0 1) substrates by the sublimation method using a TaC crucible. Raman spectrum indicates that the polytype of the grown AlN single crystals is a Wurtzite-2H type structure, and the crystals do not include any impurity phases. The quality at the top of the crystal improves as crystal thickness increases along the 〈0 0 0 1〉 direction during growth: a low etch pit density (7×10⁴ cm⁻²) and a small full width at half maximum for a 0002 X-ray rocking curve (58 arcsec) have been achieved at a thickness of ∼8 mm. The possible mechanism behind the improvement in the AlN crystal quality is also discussed.     

The first stable tetraarylacenaphthenequinodimethanes exhibiting electrochromism with ‘write-protect’ option: preparation, highly deformed structure, and reversible interconversion with acenaphthylene-5,6-diyl dicationic dyes

Severely deformed title quinodimethanes [1,2-bis(diarylmethylene)acenaphthenes] 1 have been designed and prepared as novel electrochromic materials, which can be reversibly interconverted with the deeply colored dicationic dyes 1²⁺ with acenaphthylene-1,2-diyl skeleton. The X-ray analysis of 1 revealed that the inner two aryl groups are forced to overlap in proximity, which can account for the facile electrocyclization process to the isomer. By combination of reversible electrochemical transformation with irreversible isomerization process, the present system provides a prototype for novel molecular response systems equipped with the ‘write-protect’ option.     

DNA-binding properties and photocleavage activity of cationic water-soluble chlorophyll derivatives

Three cationic water-soluble chlorin e(6) derivatives, that is, 6a-,gammab-,7c-tris(2-trimethylammonioethyl)chlorin e(6) (1), 6a-,gammab-,7c-tris(3-methylpyridiniummethyl)chlorin e(6) (2), and 6a-,gammab-, 7c-tris(2-trimethylammonioethyl)-2-(3-trimethylammonioprop-1-enyl)chlorin e(6) (3), have been designed and synthesized to allow the study of their DNA-binding and -photocleavage activities. The DNA-unwinding assay, measurements of melting temperatures of double-stranded DNA, and the induced CD and visible absorption spectra have revealed that 1 and 3 are intercalated into the base pairs of the double-helical DNA, while 2 is bound to outside the minor groove of the double-helical DNA. The cationic water-soluble chlorin e(6) derivatives effectively cleave the double-helical DNA under photoirradiation and the DNA-photocleavage activity increases in the order 3>1>2. The DNA-binding and -photocleavage characteristics of the three cationic water-soluble chlorin e(6) derivatives are influenced by aspects of their molecular structure, such as the kind, number, and position of the cationic substituents.     

Exclusive measurement of the nonmesonic weak decay of the lambda(5)He hypernucleus

We performed a coincidence measurement of two nucleons emitted from the nonmesonic weak decay of lambda(5)He formed via the 6Li(pi+, K+) reaction. The energies of the two nucleons and the pair number distributions in the opening angle between them were measured. In both np and nn pairs, we observed a clean back-to-back correlation coming from the two-body weak reactions of lambda p --> np and lambda n --> nn, respectively. The ratio of the nucleon pair numbers was N(nn)/N(np) = 0.45 +/- 0.11(stat) +/- 0.03(syst) in the kinematic region of cos theta(NN) < -0.8. Since each decay mode was exclusively detected, the measured ratio should be close to the ratio of gamma(lambda p --> np)/gamma(lambda n --> nn). The ratio is consistent with recent theoretical calculations based on the heavy meson and/or direct-quark exchange picture.     

Evaluation of the molecular recognition of monoclonal and polyclonal antibodies for sensitive detection of 2,4,6-trinitrotoluene (TNT) by indirect competitive surface plasmon resonance immunoassay

Detection of TNT is an important environmental and security concern all over the world. We herein report the performance and comparison of four immunoassays for rapid and label-free detection of 2,4,6-trinitrotoluene (TNT) based on surface plasmon resonance (SPR). The immunosensor surface was constructed by immobilization of a home-made 2,4,6-trinitrophenyl–keyhole limpet hemocyanin (TNPh–KLH) conjugate onto an SPR gold surface by simple physical adsorption within 10 min. The immunoreaction of the TNPh–KLH conjugate with four different antibodies, namely, monoclonal anti-TNT antibody (M-TNT Ab), monoclonal anti-trinitrophenol antibody (M-TNP Ab), polyclonal anti-trinitrophenyl antibody (P-TNPh Ab), and polyclonal anti-TNP antibody (P-TNP Ab), was studied by SPR. The principle of indirect competitive immunoreaction was employed for quantification of TNT. Among the four antibodies, the P-TNPh Ab prepared by our group showed highest sensitivity with a detection limit of 0.002 ng/mL (2 ppt) TNT. The lowest detection limits observed with other commercial antibodies were 0.008 ng/mL (8 ppt), 0.25 ng/mL (250 ppt), and 40 ng/mL (ppb) for M-TNT Ab, P-TNP Ab, and M-TNP Ab, respectively, in the similar assay format. The concentration of the conjugate and the antibodies were optimized for use in the immunoassay. The response time for an immunoreaction was 36 s and a single immunocycle could be done within 2 min, including the sensor surface regeneration using pepsin solution. In addition to the quantification of TNT, all immunoassays were evaluated for robustness and cross-reactivity towards several TNT analogs.