The concentration of surface VO species on oxidized vanadium oxide catalysts

The hollandite-type phase K_1.33Mg_3.11Sb_4.89O₁₆ has been studied by X-ray and electron diffraction as well as high resolution electron microscopy at 500 kV. This material was found to adopt the tetragonal hollandite structure, space group $\text{I4}\text{m}$, with a = 10.315 (4)Å; c = 3.080 (4) Å. The formation of a 3c body-centered supercell was observed and this was shown to be due to ordering of potassium cations within the tunnel sites. Computer image simulations established that ordering of the tunnel cations alone rather than the octahedrally coordinated framework cations was responsible for superlattice formation. In some crystals the supercell ordering appeared to occur in domains.     

Vacuum lithography—A completely dry lithography using plasma processing

The purpose of this paper is to describe a thoroughly dry lithography using plasma polymerization and plasma etching. The new lithography is named vacuum lithography because all processes are performed at reduced pressures. Resist films were formed in bell-jar-type and argon-flow-type reactors. The controllability of plasma polymerization is discussed with respect to the type of reactor and gas mixture. A pattern was delineated in the resist using an electron beam, and it was developed by plasma etching with a mixture of argon and oxygen. It was found that the quality of the plasma-polymerized resist depends strongly on the polymer structure and on the plasma etching conditions. In this experiment, the recorded values of sensitivity and value of plasma-polymerized methyl methacrylate were 700 µC/cm² and 1, respectively.     

Synthesis and binding studies of novel thiacalixpodands and bisthiacalixarenes having O,O″-dialkylated thiacalix[4]arene unit(s) of 1,3-alternate conformation

A series of thiacalixpodands and bisthiacalixarenes with imine units have been prepared by condensation of O,O″-bis(2-aminoethyl)-O′,O?-dipropyl-p-tert-butylthiacalix[4]arene of 1,3-alternate conformation with different aromatic (di)aldehydes. The molecules derived from pyridine-2-carbaldehyde and -2,6-dicarbaldehyde quantitatively extract silver ion from aqueous into organic phase with complete selectivity over other metal ions (Na⁺, K⁺ and Cs⁺) under neutral conditions. The former compound forms a 1:2 (L:M) complex with silver ion as proved by NMR spectroscopy, Job’s plot and X-ray crystallography.     

High Photocatalytic Activity of F-Doped TiO2 Film on Glass

The photoreactivity of sol-gel (SG)-TiO₂ films was enhanced significantly with addition of a small amount of trifluoroacetic acid (TFA) into the starting solution. The promoting effect was confirmed in two separate experiments of the methylsiloxane monolayer oxidation and the photocurrent measurements. The results of film characterization indicated that the absorption coefficient for ultraviolet light ( < 360 nm) increases due to film densification and the crystallinity is improved upon F doping. The improvement in the photoreactivity was ultimately attributed to the increase in the rate at which the photogenerated charge carriers reach the surface in the photostationary state.     

Structural Effects of Oligosaccharide-Branched Cyclodextrins on the Dual Recognition toward Lectin and Drug

Bi-galactose-branched cyclodextrins (Bi-Gal-CDs)(1–6) having different spacer arm lengths between two terminal galactoses were foundto have the optimum length for association with PNA lectin. Also, the inclusioninteraction of the drug depended on the length of the spacer arms. The dual association of thesecompounds was quantitatively evaluated by SPR and compared to the other oligosaccharide-branchedCDs (Scheme 1). The number and the length of the spacer arm are important for theassociation both with the lectin and drug for the purpose of targeting drug-delivery systems.The association constants K of bi-Gal-CD (2) with rat liver cells showed a 60 timeshigher association than with PNA. Direct evidence of the association between PNA andbi-Gal-CD (2) was characterized by AFM observations. The results obtained strongly suggested a method to find a new design for the targeting drug carrier. In order toincrease the association with the cell, a sufficient spacer arm length is necessary for the effectivedual recognition of the oligosaccharide-CDs. In order to increase the inclusion of thedrug, the CD structure of a multi-saccharide branch is necessary.     

Determination of surface V=O species of V2O5 catalysts during reaction condition by using in-situ Narp technique

NARP (Nitric oxide-Ammonia Rectangular Pulse) technique was applied for the in-situ measurement of the number of surface V=O species of V₂O₅ catalysts. When V₂O₅ catalyst was exposed to flowing benzene/O₂/N₂ mixture gas at 573–673 K, the surface concentration of V=O species decreased and finally reached a steady state which was dependent on the [O₂]/[Benzene] ratio in the feed gas. It was confirmed by XPS spectra that the decrease in the surface V=O species is attributed to the reduction of the V₂O₅ surface. Although calcination of V₂O₅ at above 873 K reduced the surface concentration of V=O species, it recovered after a cyclic reduction-oxidation treatment at 673 K, which modifies the near-surface layer of V₂O₅. The dependence of the surface V=O species on calcination temperature was correlated with the flatness of the surface and the diffusion of lattice oxygen in near-surface layer.     

Generation, reactions, and kinetics of sterically congested triplet diphenylcarbenes. Effects of bromine groups.

A series of polybrominated diphenylcarbenes (DPCs) are generated by irradiation of the corresponding precursor diazomethanes, and their reactivities are investigated by means of low-temperature spectroscopies as well as laser flash photolysis. Triplet bis(2,4,6-tribromophenyl)carbene was shown to decay by undergoing dimerization and to have a half-life of 1 s in a degassed benzene solution at room temperature, some 6 orders of magnitude longer-lived than the parent DPC. Anomalous effects of para substituents on the stability of the triplet are noted. Thus, while the replacement of a 4-bromine group with a methyl group resulted in a sharp decrease in the lifetime, introduction of a tert-butyl group resulted in a dramatic increase in the lifetime; triplet bis(2,6-dibromo-4-tert-butylphenyl)carbene was shown to have a half-life of 16 s in solution at room temperature. Attempts to increase the stability of these polybrominated DPCs by buttressing effects of a m-bromine group and by the synergetic effect of bromine and methyl groups are also described.     

Constituents of the roots of Cynanchum bungei Decne. Isolation and structures of four new glucosides, bungeiside-A, -B, -C, and -D.

Four new glucosides, bungeiside-A, -B, -C, and -D, were isolated from the roots of Cynanchum bungei Decne. The structures of the new compounds were determined by chemical and spectroscopic methods, including two-dimensional nuclear magnetic resonance (2D NMR) techniques, especially 1H-detected heteronuclear multiple-bond multiple-quantum coherence.