Versatile p‐Type Chemical Doping to Achieve Ideal Flexible Graphene Electrodes

We report effective solution‐processed chemical p‐type doping of graphene using trifluoromethanesulfonic acid (CF₃SO₃H, TFMS), that can provide essential requirements to approach an ideal flexible graphene anode for practical applications: i) high optical transmittance, ii) low sheet resistance (70 % decrease), iii) high work function (0.83 eV increase), iv) smooth surface, and iv) air‐stability at the same time. The TFMS‐doped graphene formed nearly ohmic contact with a conventional organic hole transporting layer, and a green phosphorescent organic light‐emitting diode with the TFMS‐doped graphene anode showed lower operating voltage, and higher device efficiencies (104.1 cd A^?1, 80.7 lm W^?1) than those with conventional ITO (84.8 cd A^?1, 73.8 lm W^?1).     

BODIPY/Nile‐Red‐Based Efficient FRET Pair: Selective Assay of Endoplasmic Reticulum Membrane Fluidity

We synthesized a boron‐dipyrromethene (BODIPY)/Nile Red hybrid probe capable of selectively recognizing fluidity changes in the endoplasmic reticulum (ER) membrane due to its preferential localization to the ER and strong energy transfer from BODIPY to the Nile Red moiety, emitting only in nonaqueous environments. ER membrane fluidity in HepG2 cells was markedly reduced by a cell model of metabolic syndrome.     

Enantioselective alkylation of beta-keto esters by phase-transfer catalysis using chiral quaternary ammonium salts

Catalytic enantioselective alkylation promoted by a quaternary ammonium salt from cinchonine as a phase transfer catalyst is described. Treatment of cyclo beta-keto esters with alkyl halide under mild reaction conditions afforded the corresponding alpha-alkylated beta-keto esters in moderate to excellent yields with high enantiomeric excesses     

Acceptor-dependent stereoselective glycosylation: 2'-CB glycoside-mediated direct beta-D-arabinofuranosylation and efficient synthesis of the octaarabinofuranoside in mycobacterial cell wall

[reaction: see text]. A reliable and generally applicable direct method for the stereoselective beta-arabinofuranosylation employing a 2'-carboxybenzyl arabinofuranoside as the glycosyl donor has been established. The acyl-protective group on glycosyl acceptors is essential for the beta-stereoselectivity. The power of the present acceptor-dependent glycosylation method was demonstrated by the efficient synthesis of the octaarabinofuranoside in arabinogalactan and lipoarabinomannan found in mycobacterial cell wall.     

Characterization and investigation of substrate specificity of the sugar aminotransferase WecE from E. coli K12

WecE gene, encoding a sugar aminotransferase (SAT), has been cloned from E. coli K12 and expressed in E. coli BL21 (DE3). The enzyme was purified and characterized. WecE used TDP-4-keto-6-deoxy-D-glucose (TDP-D-Glc4O) and L-glutamate as a good amino acceptor and donor, respectively, leading to the production of TDP-4-amino-4,6-dideoxy-D-galactose (TDP-Fuc4N), which was identified by NMR studies. WecE also showed a similar activity for TDP-4-keto 6-deoxy-D-mannose (TDP-D-Man4O), but no activity for GDP-4-keto-6-deoxy-D-mannose (GDP-D-Man4O), suggesting that the nucleotide moiety would become a key determinant to the substrate specificity of amine acceptor for the activity of the SAT. Multiple alignments showed that SATs have four highly conserved motifs located around the active site and could be divided into three subgroups (VIalpha, VIbeta, and VIgamma) that might be closely related with their substrate specificities.     

Solid-state interdiffusion mechanism in strained Si1–xGex/Si heterostructures

The interdiffusion in a low-strained Si_0.93Ge_0.07/Si epilayer was analyzed by double-crystal X-ray diffraction. The interdiffusion was characterized by a low diffusion barrier of 1.81 eV with a diffusion constant of 4.3 × 10⁻⁵ cm²/sec, which indicates correlation with the stacking fault generated by the homoepitaxial growth of the Si layer prior to the growth of the strained SiGe layer. At the very low-strained layer, the driving force causing the interdiffusion is the concentration gradient, and the mechanism is self-diffusion of Si. Furthermore, the interdiffusion mechanisms were classified into three groups, depending on the Ge mole fraction x. For x < 0.2, the diffusion process in the SiGe alloy is similar to a self-diffusion of Si atoms, while, for 0.2 < x < 0.4, Ge atoms prefer to be diffused out from the alloy. Finally, for x > 0.4, Si atoms can be diffused into the alloy. Received: 22 April 1997 / Accepted: 4 June 1997     

Catalytic ozonation of humic acids with Fe/MgO

Summary Degradation of humic acids by ozone was performed at room temperature in a stirred tank reactor with heterogeneous catalysts. Experimental results show that the ozonation with Fe/MgO induced a significant reduction in UV absorbance of humic acids, as compared to ozone alone. Fe/MgO was the most efficient catalyst in degradation humic acids in the presence of ozone. GPC (gel permeation chromatography) showed that humic acids with high molecular weight could be severely decomposed into organic compounds with low molecular weight by the Fe/MgO catalyst, indicating that humic acids could be catalytically decomposed.     

High‐Flux Zeolitic Imidazolate Framework Membranes for Propylene/Propane Separation by Postsynthetic Linker Exchange

While zeolitic imidazolate framework, ZIF‐8, membranes show impressive propylene/propane separation, their throughput needs to be greatly improved for practical applications. A method is described that drastically reduces the effective thickness of ZIF‐8 membranes, thereby substantially improving their propylene permeance (that is, flux). The new strategy is based on a controlled single‐crystal to single‐crystal linker exchange of 2‐methylimidazole in ZIF‐8 membrane grains with 2‐imidazolecarboxaldehyde (ZIF‐90 linker), thereby enlarging the effective aperture size of ZIF‐8. The linker‐exchanged ZIF‐8 membranes showed a drastic increase in propylene permeance by about four times, with a negligible loss in propylene/propane separation factor when compared to as‐prepared membranes. The linker‐exchange effect depends on the membrane synthesis method.     

An Organic Mixed‐Valence Ligand for Multistate Redox‐Active Coordination Networks

The multistate redox‐active/multi‐interactive ligand 5,5′,8,8′‐tetra(4‐pyridyl)‐2,2′‐(1,4‐phenylene)bis‐1H‐perimidine (H₂TPP) was designed and synthesized. H₂TPP undergoes four one‐electron oxidation steps, and was used for the preparation of a multistate redox‐active coordination network in a solid–liquid interface reaction using molten Cd²⁺ salts. The multiple redox states of H₂TPP were confirmed spectroscopically by stepwise four‐electron oxidation. Spectroscopic analysis indicated that the mixed‐valence states of the ligand are class II on the UV/Vis/NIR timescale and borderline class II/class III on the ESR timescale.     

Influence of copper precursors in the steam reforming of methanol over Cu/SnO2/SiO2 catalysts

Cu/SnO₂/SiO₂ catalysts, prepared with three different copper precursors (copper nitrate, sulfate and chloride), were characterized and investigated for the steam reforming of methanol. Cu/SnO₂/SiO₂ catalyst, prepared with copper nitrate, showed the highest activity among the tested catalysts. The highest activity of the catalyst prepared with copper nitrate was ascribed to the highly dispersed Cu particles from CO adsorption experiment. The selectivity of methanol to H₂ decreased with an increase in the amount of acid on the surface of Cu/SnO₂/SiO₂ catalysts from FT-IR experiments.This revised version was published online in December 2005 with corrections to the Cover Date.