Fluorescence study of a thermotropic liquid crystal: Bis (p-hexyloxyphenyl) terephthalate

The microstructure of the low molecular weight thermotropic liquid crystal, bis(p-hexyloxyphenyl)terephthalate (PP6), was analysed by fluorescence. The material has an emission around 400 nm in its various liquid crystalline phases, but this emission disappears in the isotropic phase. The emission was attributed to fluorescence from an intermolecular ground state complex between two different chromophores of PP6 based on fluorescence experiments of model compounds and dilute PP6 solutions. No peak shifts were observed on changing temperature, while the fluorescence intensity decreased as the temperature was increased. The fluorescence intensity changed dramatically at the phase transitions. An abrupt change in the fluorescence intensity was observed on changing depending on the temperature especially at the smectic-nematic transition temperature. Thus, the intermolecular fluorescence of the liquid crystal is greatly affected by the phase structure and the order of liquid crystalline phase.     

Highly oriented aragonite nanocrystal-biopolymer composites in an aragonite brick of the nacreous layer of Pinctada fucata

13C CP/MAS NMR and FE/TEM measurements of the aragonite brick of the nacreous layer of Pinctada fucata indicate that it assembles with highly oriented aragonite nanocrystals, which are regulated by biopolymers.     

(IMo(7)O(26))(2)](6)(-): A missing link between molecular and solid oxides

A new molecular oxide, [(IMo(7)O(26))(2)](6)(-), that has a self-contained structure has been synthesized. Its structural relevance both to the rutile structure and several molecular oxides that had been classified as "strange ones with odd structures" has given some insights as to why those species assume such structures. The novel yet self-contained nature of the structure suggests the existence of a new class of molecular oxides of related structures.     

Fabrication of photonic crystals in ZnS-doped glass

Three-dimensional photonic crystals were fabricated in a ZnS-doped silicate glass by use of a femtosecond pulsed laser. Woodpile structures consisting of 36 layers were produced by focusing with a 100x (1.35-numerical-aperture) objective. Attenuations of approximately 3-8 dB arising from a photonic bandgap were observed in the visible and the near-infrared regions.     

Enhancement of efficiency in photo-excitation to the triplet state by laser-pulse reshaping

An optical system is proposed to enhance efficiency in photo-excitation to the triplet state by reshaping an original laser pulse into a train of pulses. This optical system can be used to improve the attainable nuclear spin polarization in dynamic nuclear polarization experiments using photo-excited triplet electron spins.     

The interaction of an anionic gemini surfactant with conventional anionic surfactants

The interaction in two mixtures of an anionic gemini surfactant having N ,N -dialkylamide and carboxylate groups in a molecule, (CH2)2[N(COC11H23)CH(CO2H)CH2(CO2H)]2. 2NaOH (GA), and conventional anionic surfactants have been investigated in 0.1 M NaCl at pH 5.0. The two mixtures are GA/sodium dodecylsulfate (SDS) and GA/sodium N -dodecanoylglutamate (AGS) at a molar fraction of GA, alphaGA = 0.25 . Mixtures of both GA/SDS and GA/AGS exhibit synergism in surface tension reduction effectiveness. The GA/SDS mixture also exhibits synergism in surface tension reduction efficiency and mixed micelle formation, whereas the GA/AGS mixture does not. The interaction in mixed adsorption film formation is stronger than that in mixed micelle formation for the two mixtures. The interaction in the formation of the mixed adsorption film and the mixed micelle for the GA/SDS mixture is stronger in both formations than that for the GA/AGS mixture. The stronger interaction for the GA/SDS mixture may be caused by the combination of the smaller minimum area per molecule at the air/water interface (Amin) of the head groups in the GA molecule and the larger Amin in the SDS molecule.     

Reductive cleavage of the C-O bond of acetals and orthoesters: reduction by silane in the presence of a Rh-PPh3 complex

Reductions of acetals to ethers and of orthoester to acetal by hydrosilane using rhodium catalyst are described.