Superhydrophilicity and XPS study of boron-doped TiO2

This study examines the superhydrophilicity and chemical state of boron-doped TiO₂ prepared by the ion implantation method and explores the effect of annealing on them. XRD measurements show that the implanted sample forms a polycrystalline structure of anatase with no trace of rutile. Their water-contact angles are significantly reduced upon irradiation with ultraviolet light. The Ti 2p XPS spectra of the oxide exhibit a shoulder peak at the lower binding energy side of the main peak, whereas no shoulder is observed in single-crystal and annealed TiO₂. This suggests that the titanium ions with lower valences are produced by boron doping and they disappear on subsequent annealing. The SIMS depth profile of boron in the as-implanted TiO₂ exhibits a peak at a depth of 15-20 nm, whereas this peak disappears upon annealing. The water-contact angles increased on annealing under ultraviolet light illumination. It is concluded that the improvement in the superhydrophilicity by boron doping is due to the reduction of titanium, and the deterioration of superhydrophilicity with the subsequent annealing is due to the oxidation of reduced titanium and the inward diffusion of boron.     

Preparation and luminescence properties of tris(bipyridine) ruthenium(II)-containing vinyl polymers: Ru(bpy)2 (poly-6-vinyl-2,2′-bipyridine)Cl2 and Ru(bpy)2(poly-4-methyl-4′-vinyl-,2,2′-bipyridine)Cl2

Ruthenium (II) complex-containing polymers were prepared and characterized by absorption and luminescence spectra, luminescence quantum yield, and luminescence lifetime. The polymers are Ru(bpy)₂(poly-6-vinyl-2,′2-bipyridine)CI₂ ( 1 ) and Ru(bpy)₂(poly-4-methyl-4′-methyl-4′ -vinyl-2,2′-bipyridine)CI₂ ( 2 ). The absorption spectra and luminescence spectra of polymers 1 and 2 were substantially the same as that of Ru(bpy)₃CI₂. The lifetime of polymers 1 and 2 was similar to that of the respective monomer model compounds. The lifetime of polymer 1 was very short (ca. 13 ns) in comparison to Ru(bpy)₃CI₂ (660 ns), whereas the lifetime of polymer 2 (660 ns) was similar to that of Ru(bpy)₃CI₂. The temperature-dependency of the lifetime was discussed in terms of Watts' model.     

Application of esca to semi-quantitative surface and state analysis of iron oxides

In order to study oxidation states in the surface analysis of solids, a semi-quantitative ESCA (X-ray photoelectron spectroscopy-XPS and X-ray-excited Auger-electron spectroscopy-XAES) method was proposed. Taking iron-oxygen compounds as examples, the summation or subtraction technique was utilized in the analysis of ESCA spectra to identify the co-ordination type and crystal structure. The "XAES intensity factors" for the lines Cr L(3)M(2,3)M(4,5), Ti L(3)M(2,3)M(4,5) and from Fe L(3)M(4,5)M(4,5) to Zn L(3)M(4,5)M(4,5) were estimated and their occurrence discussed.     

Stereochemistry of protected ornithine side chains of gramicidin S derivatives: X-ray crystal structure of the bis-Boc-tetra-N-methyl derivative of gramicidin S

An X-ray crystallographic analysis of the bis-Ndelta-Boc-tetra-Nalpha-methyl derivative of gramicidin S, cyclo(-Val-MeOrn(Boc)-Leu-d-MePhe-Pro-)2, was undertaken successfully (R-factor = 0.088). As expected, the main chain adopts an antiparallel pleated beta-sheet conformation, but the pleated sheet is slightly twisted, and the sense of twisting is opposite to that found in the reported crystal structures of the gramicidin S-urea complex and the bis-Ndelta-(trichloroacetyl) and bis-Ndelta-(m-bromobenzoyl) derivatives of gramicidin S. In agreement with the observed resistance toward N-methylation, the urethane NH groups of the protected Orn side chains are hydrogen bonded to the carbonyl groups of the d-Phe residues. However, the side-chain-main-chain hydrogen bonding is in the i --> i - 3 mode, although hydrogen bonding in the i --> i + 2 mode was deduced from a 1H NMR study of protected gramicidin S derivatives and was actually found in the crystal structures of the diacylated gramicidin S.     

3 + 2] Cycloreversion of bicyclo[m.3.0]alkan-3-on-2-yl-1-oxonium ylides to alkenyloxyketenes. Stereospecific aspect

Rhodium(II)-catalyzed intramolecular reaction of diazoketones 1 bearing a cyclic ethereal moiety transiently formed bicyclo[m.3.0]octan-3-one-1-oxonium-2-ylides (2), which underwent sigmatropic and stereospecific [3 + 2] cycloreversion reaction to form alkenyloxyketenes 3. The ketenes were efficiently trapped by methanol to form the corresponding esters 4. Mechanistic studies revealed that the size of ethereal ring can be variable at least from THF to the THP, oxepane, and oxocane moiety, i.e., m = 3-6. On the other hand, the size of the ylide ring containing the carbonyl unit is limited to a five-membered ring. The cycloreversion was found to be stereospecific as was proven by the reactions of diastereoisomeric pairs bearing a methyl group at the bond-cleaving position. From threo isomers 7, (E)-alkenyloxyacetates 15 were exclusively formed (77-84%), whereas from erythro isomers 8, (Z)-isomers 16 were formed (80-88%). Mechanism of the cleavage from diazoacetonyl-substituted cyclic ethers to alkenyloxyketenes via bicyclic oxonium ylides was analyzed on the basis of calculations employing the hybrid density functional B3LYP and the highly correlated quadratic configuration interaction QCISD method to reveal that the concerted [3 + 2] cycloreversion is the key step of this reaction.     

Application of an Al-Ti alloy target in surface analysis by X-ray photoelectron spectroscopy

An X-ray target of an Al-Ti alloy was used in the determination of the composition of the surface layer (0-200 A thick) of a Cu-Zn alloy.     

Rotaxane-stabilized thiophosphonium salt from disulfide and phosphine

The reaction of a rotaxanated disulfide with hexamethylphosphorustriamide afforded a stable thiophosphonium salt in rotaxanated form. The structure of the thioposphonium salt was confirmed by spectroscopic and X-ray crystal structure analyses. The successful isolation of this salt was attributed to the special stabilization capability of the rotaxane structure. [reaction: see text]     

Three- to six-carbon ring-enlargement reaction of cyclic ortho esters bearing a diazocarbonyl side chain. Use of the intramolecular formation of tricyclooxonium ylides

Two types of bicyclic ortho esters 14 and 18, which are tethered to a diazocarbonyl group by polymethylene linkages--(CH2)n--of different lengths (n = 1-3 for 14 and 1-4 for 18), were prepared and catalytically decomposed by treatment with Rh2(OAc)4 either in the presence or absence of a protic nucleophile (MeOH, PhOH, AcOH) to give ring-enlargement product lactones 25 and 30 of different sizes. With 14, the enlargement took place when n = 1 or 2, but not when n = 3. With 18, in which the diazo carbon is substituted with a methoxycarbonyl group, the length of the chain can be extended further to n = 4 to obtain ring-enlargement products or their derivatives. All of these reactions could be explained in terms of the intermediacy of tricyclooxonium ylides 22 and 28. The ylides form an equilibrium with the corresponding ring-opened zwitterions 22' and 28', respectively, which, after protonation by a protic nucleophile, undergo mainly ring-enlargement to form medium-sized or large oxalactones rather than 1,2-rearrangement.