Degradation of Methylene Blue by RF Plasma in Water

Radio frequency (RF) plasma in water was used for the degradation of methylene blue. The fraction of decomposition of methylene blue and the intensity of the spectral line from OH radical increased with RF power. RF plasma in water also produced hydrogen peroxide. The density of hydrogen peroxide increased with RF power and exposure time. When pure water (300 mL) is exposed to plasma at 310 W for 15 min, density of hydrogen peroxide reaches to 120 mg/L. Methylene blue after exposed to plasma degraded gradually for three weeks. This degradation may be due to chemical processes via hydrogen peroxide and tungsten. The comparison between the experimental and calculated spectral lines of OH radical (A–X) shows that the temperature of the radical is around 3,500 K. Electron density is evaluated to be ?3.5 × 10²⁰ m^?3 from the stark broadening of the H_β line.     

Synthesis of all-conjugated diblock copolymers by quasi-living polymerization and observation of their microphase separation

We designed and synthesized the all-conjugated diblock copolymers poly(3-hexylthiophene-block-3-(2-ethylhexyl)thiophene)s (P(3HT-b-3EHT)s) via a modified Grignard metathesis (GRIM), a type of quasi-living polymerization, and studied their microphase-separated structures. The P(3HT-b-3EHT)s synthesized had well-controlled molecular weights and very narrow polydispersity indices (PDIs), which demonstrates the usefulness of GRIM polymerization for the synthesis of semiconducting block copolymers. P(3HT-b-3EHT)s self-organized to form clear microphase-separated patterns upon thermal treatment, as observed by AFM. Interestingly, the enhancement of the interchain interaction of the P3HT segments compared with the P3HT homopolymer was clearly observed from the UV-vis spectra, despite the fact that the amount of crystalline P3HT fraction was reduced to 83% of the total polymer amount in P(3HT-b-3EHT). It is suggested that the relatively unconstrained, amorphous segments of P3EHT can enhance the crystallization of P3HT segments to form an ordered self-organized nanostructure.     

Site-specific synthesis of oxo-bridged mixed-valence binuclear complexes on mesoporous silica

We report the site-specific synthesis of mixed valence TiIV-O-FeII complexes within the pores of ordered mesoporous silica (SBA-15). By using 6-di- tert-butylpyridine as the selective activator of tripodally linked TiIV-OH groups of Ti-grafted SBA-15, the FeCl2.4H2O complexes reacted selectively with the nucleophilic TiIV-O(-) groups. The formation of Si-O-FeII byproducts, due to the reaction with the abundant Si-OH groups, was successfully restricted and the selectivity for forming the TiIV-O-FeII complexes exceeded 80%. The metal-metal interaction of TiIV-O-FeII complexes was confirmed by the appearance of TiIV/FeII --> TiIII/Fe III metal-to-metal charge transfer band, and their coordination, valency, and spin state were characterized by diffuse transmission UV-vis, Fourier transform IR, and Fe K-edge X-ray absorption fine structure measurements. It was also confirmed that the present methods can be extended to other metal combinations of TiIV-O-NiII and TiIV-O-MnII. The electron transfer processes occurring under photoinduced metal-to-metal charge transfer of oxo-bridged mixed valence complexes on silica supports have recently been proven as a new class of visible-light-sensitive redox centers. Thus, the present synthetic procedure allows the fabrication of a variety of photochemical reaction centers according to the molecular-level design.     

Lateral phase separation in cholesterol/diheptadecanoylphosphatidylcholine binary bilayer membrane

We investigated the phase behavior of cholesterol/diheptadecanoylphosphatidylcholine (C17:0-PC) binary bilayer membrane as a function of the cholesterol composition (X(ch)) by fluorescence spectroscopy using 6-propionyl-2-(dimethylamino)naphthalene (Prodan) and differential scanning calorimetry (DSC). The fluorescence spectra showed that the wavelength at the maximum intensity (lambda(max)) changed depending on the bilayer state: ca. 440 nm for the lamellar gel ( [Formula: see text] or L(beta)) and the liquid ordered (L(o)) phases and ca. 490 nm for the liquid-crystalline (L(alpha)) phase. The transition temperatures were determined from the temperature dependence of lambda(max) and endothermic peaks of the DSC thermograms. Both measurements showed that the pre- and main transition disappear around X(ch)=0.05 and 0.30, respectively. The constructed temperature-X(ch) phase diagram resembled a typical phase diagram for a eutectic binary mixture containing a peritectic point. The presence of a peritectic point at X(ch)=0.15 suggested that a complex of cholesterol and C17:0-PC is stoichiometrically formed in the gel phase. Consideration based on the hexagonal lattice model revealed that the compositions of 0.05 and 0.15 correspond to the bilayer states where cholesterol molecules are regularly distributed in different ways. The former is nearly equal to the composition for the membrane occupied entirely with Units (1:18), composed of a cholesterol and 18 surrounding C17:0-PC molecules within the next-next nearest neighbor sites. The latter is represented by a Unit (1:6), including a cholesterol and 6 surrounding C17:0-PC molecules. Further, the disappearance of the main transition at X(ch)=0.30 indicates that the pure L(o) phase can exist in X(ch)>0.30. The eutectic behavior observed in the phase diagram was explainable in terms of phase separation between two different types of regions with different types of regular distributions of cholesterol.     

Adsorption properties and photocatalytic activity of TiO2 and La-doped TiO2

Photocatalysts of TiO₂ and La-doped TiO₂ were prepared by calcining the pure TiO₂ sols and the sols mixed with La(NO₃)₃⋅6H₂O at 873 K, respectively. These photocatalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and N₂ adsorption-desorption isotherms measurement. As results, the BET surface area, pore diameter, mesopore volume and micropore volume slightly increased, while the crystallite size and the phase structure were little affected by lanthanum doping. The equilibrium adsorption of methylene blue (MB) on the photocatalysts were measured in a dark room. The adsorption isotherms were confirmed to fit to the Langmuir theory. Photocatalytic activities of the photocatalysts were studied by employing the photocatalytic degradation of MB in water and degradation of acetaldehyde in air under UV-irradiation using a black light. Kinetic analysis revealed that the rate controlling steps could be the surface reaction of the adsorbed MB on the catalyst surface for MB degradation and the reaction of adsorbed acetaldehyde with the gaseous acetaldehyde for degradation of acetaldehyde, respectively.     

Synthesis, properties, and redox behavior of mono-, bis-, and tris[1,1,4,4,-tetracyano-2-(1-azulenyl)-3-butadienyl] chromophores binding with benzene and thiophene cores

Mono-, bis-, tris-, and tetrakis(1-azulenylethynyl)benzene and mono- and bis(1-azulenylethynyl)thiophene derivatives 5-10 have been prepared by Pd-catalyzed alkynylation of ethynyl arenes with 1-iodoazulene derivative or the 1-ethynylazulene derivative with tetraiodobenzene and iodothiophenes under Sonogashira-Hagihara conditions. Compounds 5-10 reacted with tetracyanoethylene in a [2+2] cycloaddition reaction to afford the corresponding 1,1,4,4,-tetracyano-2-(5-isopropyl-3-methoxycarbonyl-1-azulenyl)-3-butadienyl chromophores 12-16 in excellent yields, except for the reaction of the tetrakis(1-azulenylethynyl)benzene derivative. 1,1,4,4,-Tetracyano-2,3-bis(1-azulenyl)butadiene (17) was also prepared by the similar reaction of bis(1-azulenyl)acetylene (11) with tetracyanoethylene (TCNE). The redox behavior of novel azulene derivatives 12-17 was examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed multistep electrochemical reduction properties. Moreover, a significant color change was observed by visible spectroscopy under electrochemical reduction conditions.     

Cell processing on polyimide surface patterned by rubbing

In this study, we prepared a novel rubbed fluorinated polyimide film using a rubbing machine with a rubbing cloth and determined the surface properties of the rubbed film using an atomic force microscope and contact angle measurements. In addition, we evaluated the cell adhesion behavior on the rubbed polyimide film using a phase contrast microscope. Interestingly, a rubbed polyimide surface having a micrometer‐scale grooved pattern was prepared by the rubbing method, and the morphologies of rat primary hepatocytes and human liver cell lines attached to the rubbed surface were three‐dimensional multicellular spheroids, while the cells on an unrubbed surface showed two‐dimensional monolayers. This initial study indicates that the rubbing method without any chemical modification is simple and can easily produce large surface areas, suggesting that the rubbing may become a novel cell culture method. Copyright © 2008 John Wiley & Sons, Ltd.     

Efficient total synthesis of (+)-negamycin, a potential chemotherapeutic agent for genetic diseases

Herein, we describe an efficient strategy for the total synthesis of (+)-negamycin using commercially available achiral N-Boc-2-aminoacetaldehyde as starting material with 42% overall yield for a limited number of steps.     

Total Synthesis of Siomycin A: Construction of Synthetic Segments

The five practical segments for the total synthesis of siomycin A, that is, the dehydropiperidine segment A ( 5 ), the pentapeptide segment B ( 3 ), the dihydroquinoline segment C ( 6 ), and the β‐phenylselenoalanine dipeptide segments D ( 7 ) and E ( 4 ), were synthesized. Segment A ( 5 ) was constructed by the coupling of the azomethine ylide and the chiral sulfinimine, followed by the stereoselective reduction of the six‐membered imine function. Segment B ( 3 ) was synthesized by the phenylselenylation of the β‐lactone, stereoselective vinylzinc addition to the chiral sulfinimine, and oxazoline–thioamide conversion. Segment C ( 6 ) was prepared by the one‐pot olefination of the tetrahydroquinoline N‐oxide using triflic anhydride and triethylamine, stereoselective reduction of the methyl ketone function, and regioselective Yb(OTf)₃‐catalyzed epoxide opening by the amino group. Segments D ( 7 ) and E ( 4 ) were synthesized by coupling of the properly protected β‐phenylselenoalanines.     

Total Synthesis of Siomycin A: Completion of the Total Synthesis

The total synthesis of siomycin A ( 1 ), a representative compound of the thiostrepton family of peptide antibiotics, was achieved by incorporating the five synthetic segments A ( 2 ), B ( 3 ), C ( 4 ), D ( 5 ), and E ( 6 ). The dehydropiperidine segment A ( 2 ) was esterified with the dihydroquinoline segment C ( 4 ), and the subsequent coupling with the β‐phenylselenoalanine dipeptide segment D ( 5 ) at the segment C portion followed by lactamization between the segments A and D gave segment A‐C‐D ( 27 ). This was amidated with the pentapeptide segment B ( 3 ) at the segment A portion followed by one‐pot cyclization (between segments A and B) and elongation (with the β‐phenylselenoalanine dipeptide segment E ( 6 ) at the segment A portion), thus furnishing siomycin A ( 1 ).