Lignin-Silica-Titania Hybrids as Precursors for Si–Ti–C–O Fibers

Lignin-silica-titania and lignin-titania hybrid fibers have been prepared by sol-gel processing from lignin, tetraethoxysilane, and titanium tetrakis(2,4-pentanedionate) using a mixture of 2,4-pentanedione and tetrahydrofuran as solvent and H2SO4 as catalyst. Amounts of H2O and H2SO4, to add to the solutions with the Si-to-Ti atomic ratios of 0–1.0, were determined for achieving favorable spinnability of fibers from the solutions. The FT-IR spectrum of the fibers indicated the formation of hybrid fibers. The hybrid fibers, cured in air to avoid coalescense, could be converted into Si–Ti–C and TiC fibers upon pyrolysis at 1500°C in Ar.     

Holographic recording using visible-light sensitive polymers based on cationic polycondensation

Negative-working photopolymers based on a cationic polycondensation mechanism were developed. The photopolymers are highly sensitive to 488 nm argon ion laser light, because they use a chemically amplified reaction and are not sensitive to ambient oxygen. These photopolymers are composed of a poly(p-hydroxystyrene) matrix, a hexamethoxy methylmelamine crosslinker and a 2,4,6-tris(trichloromethyl)-1,3,5-triazine–coumarin dye combination as a photo-initiator. They exhibit 0.6 mJ/cm² (D^0.7_g) sensitivity to 488 nm light, as well as a high resolution of 0.5 μm. Due to their high sensitivity and high resolution, a relief-type hologram, larger than 50 × 50 cm, can be recorded in a short exposure time using them.     

Novel stable fluorophore, 6-methoxy-4-quinolone, with strong fluorescence in wide pH range of aqueous media, and its application as a fluorescent labeling reagent

6-Methoxy-4-quinolone (6-MOQ, 1), an oxidation product derived from 5-methoxyindole-3-acetic acid, is a novel fluorophore, which has several useful characteristics for biomedical analysis. Compound 1 has strong fluorescence with a large Stokes' shift in aqueous media, and the maximum fluorescence excitation and emission wavelengths are 243 nm and 374 nm, respectively. The molar absorptivity at the maximum excitation wavelength and fluorescence quantum yield in aqueous 10% (v/v) methanol are 32 600 L mol(-1) cm(-1) and 0.38, respectively. The fluorescence intensity of 1 is scarcely affected by changing the medium pH, showing strong fluorescence from pH 2.0 to 11.0. In addition, 1 is highly stable against light and heat, and no degradation was observed at 60 degrees C for 3 days with exposure to daylight. As a fluorescent labeling reagent, [(6-methoxy-4-oxo-1,4-dihydroquinolin-3-yl)methyl]amine (6-MOQ-NH2, 2) was synthesized, and determination of carboxylic acids was demonstrated; 50 pmol of standard propionic acid and isobutyric acid were derivatized, and the obtained S/N ratios for 10 fmol (injection amount) of these two acids were 206 and 164, respectively.     

Acid generation and deprotecting reaction by diphenyliodonium 9,10-dimethoxyanthracene-2-sulfonate in a novolak positive photoresist based on chemical amplification

In a positive photoresist composed of diphenyliodonium 9,10-dimethoxyanthracene-2-sulfonate as a novel photoacid generator, bisphenol A protected with tertbutoxycarbonyl group as a dissolution inhibitor, and a novolak resist matrix, the efficiency of photo-acid generation and deprotective reaction were investigated by means of UV-visible and IR spectroscopies. The quantitative measurement of photogenerated acid by using the acid-sensitive dye exhibited 0.18 as the quantum yield of acid generation in novolak resin film. The lithographic evaluation of this system as a chemically amplified resist was studied. The catalytic chain length for the acid-catalyzed deprotection step was determined as about 100 when 10 min post-exposure bake (PEB) at 80°C was given. The sensitivity and the resolution as a positive resist are 180 mJ/cm² and higher than 1 μm, respectively under the PEB conditions mentioned above.     

Total synthesis of the antitumor antibiotic (+/-)-fredericamycin A by a linear approach

A linear approach to the total synthesis of racemic fredericamycin A (1) through the oxidative intramolecular [4 + 2] cycloaddition of a (phenylthio)acetylene-cobalt complex is described, which is applicable for the asymmetric total synthesis of naturally occuring 1. The highlight of this work is the aromatic Pummerer-type reaction with 1-ethoxyvinyl chloroacetate, which effects the introduction of the oxygen functional group to the internal B-ring of the highly functionalized, congested polyaromatic ABC-ring moiety.     

Determination of trace elements in a silicon single crystal

Instrumental neutron activation analysis was applied to the determination of trace impurity elements in a silicon single crystal. Impurity concentrations in polysilicon melt were compared with those in a single crystal. Impurity concentrations in artificial quartz were also compared with those in natural quartz. Segregation coefficients in Au, Ir and Sb were determined at different concentrations. The segregation coefficient of an element in a silicon single crystal is constant over a critical concentration, it becomes larger gradually under the critical one, and at last it becomes larger than 1.     

Second harmonic generation-based coherent vibrational spectroscopy for a liquid interface under the nonresonant pump condition

The molecular dynamics in the low-frequency region (0-500 cm(-1)) sensitively reflects the intermolecular interactions in a liquid. The second harmonic generation-based coherent vibrational spectroscopy (SHG-CVS) was developed to monitor the low-frequency dynamics of molecules at a liquid interface, which was difficult to access by using the present spectroscopic techniques such as sum frequency generation or attenuated total reflection (ATR)-IR. Background-free detection with the transient grating (TG) optical configuration was adopted to obtain the weak signal under the electronically nonresonant pump condition. It was demonstrated that the S/N ratio of the SHG-CVS with the TG configuration was remarkably superior to that with the conventional time-resolved SHG configuration, and the improved detection limit enabled us to detect the low-frequency dynamics of coumarin 314 molecules at the air/water interface under the electronically nonresonant pump condition.     

Spontaneous copolymerization of 4-methylene-1,3-dioxolanes with maleic anhydride

The copolymerization of methylenedioxolanes, such as 4-methylene-1,3-dioxolane (I) and 2,2-dimethyl-4-methylene-1,3-dioxolane (II), with maleic anhydride (Manh) gives rise spontaneously to the alternating copolymers by the participation of charge-transfer (CT) complexes. The formation of CT complexes I-Manh and II-Manh was ascertained by UV and NMR spectroscopies. The equilibrium constants (K) could not be determined but were assumed to be small (K ? 1). For comparison with these systems an investigation of I-dimethyl maleate (DMM) and II-DMM systems was carried out to estimate K values 0.115 and 0.157 L/mol, respectively. To clarify the copolymerization mechanism I-Manh-acryronitrile was terpolymerized. Consequently it was concluded that the spontaneous copolymerization of I-Manh and II-Manh systems is effected by the CT complex monomer mechanism.