Microemulsions from silicone oil with an anionic/nonionic surfactant mixture

Microemulsion phases have been prepared for the first time from the silicone oil "M(2)" (hexamethyldisiloxane) and a surfactant mixture of a nonionic surfactant "IT 3" (isotridecyltriethyleneglycolether) and an ionic surfactant Ca(DS)(2) (calciumdodecylsulfate). For such a surfactant mixture the hydrophilicity of the system can be tuned by the mixing ratio of the two components. With increasing IT 3 content, the surfactant mixtures show a L(1)-phase, a wide L(α)-region and a narrow L(3) sponge phase. For constant temperature, two single phase channels exist in the microemulsion system. The lower channel (low IT 3 content) ends in the middle of the phase diagram with equal amounts of water and oil, the upper channel begins with the L(3)-phase and passes all the way to the oil phase. Conductivity data show that the upper channel has a bi-continuous morphology up to 40% oil while the lower channel consists of oil droplets in water. In contrast to previous studies on nonionic systems, the two single phase channels are not connected and microemulsions with equal amount of oil and water do not have a bicontinuous structure.     

Electrochemical quartz crystal microbalance analysis of the oxygen reduction reaction on Pt-based electrodes. Part 1: Effect of adsorbed anions on the oxygen reduction activities of Pt in HF, HClO4, and H2SO4 solutions

The effects of anion adsorption on the activities for the oxygen reduction reaction (ORR) at a Pt film electrode in electrolyte solutions (HClO(4) and HF at various concentrations) were analyzed using an electrochemical quartz crystal microbalance (EQCM) and a rotating disk electrode (RDE). With an increasing HClO(4) concentration [HClO(4)], the onset potential for the Pt oxide formation in the voltammogram shifted in the positive direction, accompanied by a compression of the hydrogen adsorption/oxidation wave to less positive potentials. This is ascribed to a specific adsorption of the ClO(4)(-) anion, because the [HClO(4)] dependence of the mass change Δm detected by EQCM in the double-layer region was found to be fitted well by a Frumkin-Temkin adsorption isotherm. The potential dependencies of Δm in both 0.1 and 0.5 M HClO(4) solutions accord well with those of the ν(Cl-O) intensities observed by in situ Fourier transform infrared (FTIR) spectroscopy in the potential range from 0.3 to 0.6 V. The kinetically controlled current densities j(k) for the ORR at the Pt-RDE were found to decrease with increasing [HClO(4)], because of the blocking of the active sites by specifically adsorbed ClO(4)(-). The values of j(k) in the non-adsorbing 0.1 M HF electrolyte solution, however, were smaller than those in 0.1 M HClO(4). It was found that the low ORR activity could be ascribed to the low H(+) activity in the weak acid solution of HF. We, for the first time, detected a reversible mass change for one or more adsorbed oxygen species on the Pt-EQCM in O(2)-saturated and He-purged HF and HClO(4) solutions. The coverages of oxygen species θ(O) on Pt were found to increase in the O(2)-saturated solution. High values of θ(O) in O(2)-saturated 7 mM HF suggest that the ORR rate was limited by the very low H(+) activity in the solution, and the adsorbed oxygen species remained on the surface because of a slow consumption rate.     

Stelleralides A-C, novel potent anti-HIV daphnane-type diterpenoids from Stellera chamaejasme L

Three novel 1-alkyldaphnane-type diterpenes, stelleralides A-C (4-6), and five known compounds were isolated from the roots of Stellera chamaejasme L. The structures of 4-6 were elucidated by extensive spectroscopic analyses. Several isolated compounds showed potent anti-HIV activity. Compound 4 showed extremely potent anti-HIV activity (EC(90) 0.40 nM) with the lowest cytotoxicity (IC(50) 4.3 μM) and appears to be a promising compound for development into anti-AIDS clinical trial candidates.     

Palladium-catalyzed borylation of sterically demanding aryl halides with a silica-supported compact phosphane ligand

Immobile but active: A silica-supported "compact" phosphane, Silica-SMAP, can be used in the Pd-catalyzed borylation of aryl chlorides or bromides with bis(pinacolato)diboron. The Silica-SMAP/Pd system significantly expands the substrate scope of the borylation toward sterically and electronically challenging aryl halides.     

Catalytic conversion of cellulose into 5-hydroxymethylfurfural in high yields via a two-step process

As a key renewable chemical for plastics and fine chemicals, the preparation of 5-hydroxymethylfurfural (5-HMF) from biomass is an important research topic. Cellulose, although abundant in nature, is difficult to convert to 5-HMF in good yields due to its recalcitrant and heterogeneous nature. In this work, we show an efficient two-step process for converting microcrystalline cellulose into 5-HMF with ionic liquids under mild conditions. In the first step, high glucose yields of above 80% could be obtained from the cellulose hydrolysis by a strong acidic cation exchange resin in 1-ethyl-3-methyl imidazolium chloride ([EMIM][Cl]) with gradual addition of water. In the second step, the resin was separated from the reaction mixture and CrCl₃ was added which lead to a 5-HMF yield of 73% based on cellulose substrate. The strategy can allow practical conversion of biomass into bio-derived products.     

Lewis Acid-Induced Reaction of γ,δ-Epoxy Tin Compounds

γ,δ-Epoxy tin compounds underwent divergent reactions depending upon the substitution pattern of the substrates as well as upon Lewis acids used as the indueer.     

Preparation of the visible light responsive TiO2 thin film photocatalysts by the RF magnetron sputtering deposition method

TiO₂ thin film photocatalysts which could induce photoreactions under visible light irradiation were successfully developed in a single process by applying an ion engineering technique, i.e., the radio frequency (RF) magnetron sputtering deposition method. The TiO₂ thin films prepared at temperatures greater than 773 K showed the efficient absorption of visible light; on the other hand, the TiO₂ thin films prepared at around 573 K were highly transparent. This clearly means that the optical properties of TiO₂ thin films, which absorb not only UV but also visible light, can be controlled by the preparation temperatures of the RF magnetron sputtering deposition method. These visible light responsive TiO₂ thin films were found to exhibit effective photocatalytic reactivity under visible light irradiation (λ > 450 nm) at 275 K for the reductive decomposition of NO into N₂ and N₂O. From various characterizations, the orderly aligned columnar TiO₂ crystals could be observed only for the visible light responsive TiO₂ thin films. This unique structural factor is expected to modify the electronic properties of a TiO₂ semiconductor, enabling the efficient absorption of visible light.     

Separate evolution of H2 and O2 from H2O on visible light-responsive TiO2 thin film photocatalysts prepared by an RF magnetron sputtering method

Visible light-responsive TiO₂ thin film photocatalysts (Vis-TiO₂) have been prepared on Ti metal foil (Vis-TiO₂/Ti) or ITO glass (Vis-TiO₂/ITO) substrates by a radio-frequency magnetron sputtering (RF-MS) method. The UV–Vis spectra as well as photoelectrochemical performance of Vis-TiO₂ were affected by various calcination treatments such as calcination in air or NH₃. Calcination treatment in NH₃ (1.0 × 10⁴ Pa, 673 K) was particularly effective in increasing the visible light absorption of Vis-TiO₂ as well as in enhancing its photoelectrochemical performance and photocatalytic activity. A novel Vis-TiO₂ thin film photocatalyst (Vis-TiO₂/Ti/Pt) was prepared by an RF-MS method where Vis-TiO₂ was deposited on one side of a Ti metal foil substrate and nanoparticles of Pt were deposited on the other side. The separate evolution of H₂ and O₂ from H₂O could be successfully achieved by using an H-type glass cell consisting of two aqueous phases separated by Vis-TiO₂/Ti/Pt and a proton-exchange membrane. It was found that the rate of the separate evolution of H₂ and O₂ was also dramatically enhanced by calcination treatment of Vis-TiO₂ in NH₃.     

Centrifugal precipitation chromatography,a powerful technique for the isolation of active enzymes from tea leaves (Camellia sinensis)

Centrifugal precipitation chromatography was developed approximately 10 years ago. In contrast to other counter-current chromatographic techniques, the centrifugal precipitation chromatography system is operated with two mutually miscible solutions separated by a cut-off membrane. Centrifugal precipitation chromatography was firstly introduced for the separation of proteins using an ammonium sulfate gradient. In this study we describe a novel approach using solvent-based protein precipitation for the isolation of active plant enzymes from tea leaves (Camellia sinensis) by centrifugal precipitation chromatography. We developed a gradient based on acetone and Tris-buffer, because the biological activity of carotenases in tea leaves cannot be preserved in the presence of ammonium sulfate. Parameters such as the critical solvent concentration, flow rate, buffer concentration, and sample load were determined and/or optimized. Subsequently, the newly developed separation protocol was successfully used for the isolation of active carotenoid cleavage enzymes from tea leaves. The isolated enzymes showed high enzymatic activities and purities and could be directly used for enzymatic assays and structure elucidation.