Synthesis of anatase-type TiO2 films by reactive laser ablation of a metallic Ti target in ambient O2 gas

TiO₂ films having anatase-type crystal structures were synthesized by reactive laser ablation of a metallic Ti target in ambient O₂ gas. The anatase-type TiO₂ was obtained at O₂ pressures below 0.2 Torr and at substrate temperatures above 150 °C. The films had the (101) orientation at substrate temperatures of 200–250 °C while, at substrate temperatures of 400–450 °C, the orientation of the films was (004). Rutile-type crystal was mixed in at substrate temperatures higher than 450 °C. The synthesis characteristics were compared with the fluxes of Ti, Ti⁺, and TiO toward the substrate, which were evaluated by laser-induced fluorescence imaging spectroscopy. PACS 81.15.Fg; 61.10.-i; 52.70.Kz     

Use of thiosemicarbazide as masking agent for the direct determination of bismuth in copper by atomic-absorption spectrometry with hydride generation

A simple atomic-absorption method for determining trace bismuth in copper metal is described. Interference from the matrix is eliminated by masking copper with thiosemicarbazide in acidic solution.     

Comparative study of IBMK and DIBK as extraction solvents in strongly acidic media: extraction behaviour and kinetic stability of Cu(PCD)(2) in these solvents

The use of di-isobutyl ketone (DIBK) and isobutyl methyl ketone (IBMK) as the solvent for extraction of copper(II) from strongly acidic media (0.01-8M hydrochloric acid) with ammonium l-pyrrolidinecarbodithioate has been studied. In contrast to IBMK, the volume of the DIBK extract remains the same, irrespective of the acidity of the aqueous phase. A certain amount of free acid is transferred into both solvents, and affects the kinetic stability of the chelate extracted; the free acid can be completely removed by washing the extract with water, and partly by filtering it through a dry filter paper. However, the chelate extracted into DIBK exhibits excellent stability without such treatment, since the amount of free acid in DIBK is much smaller than that in IBMK. When DIBK is used, the copper chelate can be quantitatively extracted as long as the extraction is done from acidic media.     

Formation of cavitation-induced pits on target surface in liquid-phase laser ablation

It is well known that a crater is formed on the target surface by the irradiation of intense laser pulses in laser ablation. In this work, we report that additional pits are formed on the bottom surface of the ablation crater due to the collapse of a cavitation bubble in liquid-phase laser ablation. We observed the formation of several cavitation-induced pits when the fluence of the laser pulse used for ablation was approximately 5 J/cm². The number of cavitation-induced pits decreased with the laser fluence, and we observed one or two cavitation-induced pits when the laser fluence was higher than 10 J/cm². In addition, we examined the influence of the liquid temperature on the formation of cavitation-induced pits. The collapse of the cavitation bubble was not observed when the liquid temperature was close to the boiling temperature, and in this case, we found no cavitation-induced pits on the bottom surface of the ablation crater. This experimental result was discussed by considering the cavitation parameter.     

Infrared multiphoton dissociation spectroscopic analysis of peptides and oligosaccharides by using fourier transform ion cyclotron resonance mass spectrometry with a midinfrared free-electron laser

The fragmentation of peptides and oligosaccharides in the gas phase was investigated by means of electrospray ionization Fourier transform ion cyclotron resonance (FTICR) mass spectrometry coupled with dissociation by a laser-cleavage infrared multiphoton dissociation (IRMPD) technique. In this technique, an IR free-electron laser is used as a tunable source of IR radiation to cause cleavage of the ionized samples introduced into the FTICR cell. The gas-phase IRMPD spectra of protonated peptides (substance P and angiotensin II) and two sodiated oligosaccharides (sialyl Lewis X and lacto-N-fucopentaose III) were obtained over the IR scan range of 5.7-9.5 microm. In the IRMPD spectra for the peptide, fragment ions are observed as y/b-type fragment ions in the range 5.7-7.5 microm, corresponding to cleavage of the backbone of the parent amino acid sequence, whereas the spectra of the oligosaccharides have major peaks in the range 8.4-9.5 microm, corresponding to photoproducts of the B/Y type.     

Characterization of [ZnO]m[ZnMgO]n multiple quantum wells grown by molecular beam epitaxy

Thermal stability of single-crystalline [ZnO]_m[Zn_0.7Mg_0.3O]_n multiple quantum wells (MQWs) grown on a-plane sapphire substrates by plasma-assisted molecular beam epitaxy is reported. X-ray diffraction analysis revealed that these MQWs were grown as designed with a fixed Zn_0.7Mg_0.3O barrier width of and a series of ZnO well widths of . Cathodoluminescence spectra from these MQWs consisted of two major peaks; one was the emission from the bound excitons in Zn_0.7Mg_0.3O barrier layers, and the other was that from the confined excitons in ZnO well layers. These structural and optical properties were found to be dramatically changed by the ex situ annealing treatments over 700 °C. These changes were presumably due to the onset of phase separation of the Zn_0.7Mg_0.3O barrier layers with pronounced Mg diffusion toward the ZnO wells.     

Structural and magnetic ordering in the VxNb1+yS2 system

The influence of composition on the structural ordering and magnetism in the V_xNb_1+yS₂ system has been investigated by X-ray diffraction and magnetic measurements. Stoichiometric V_1/3NbS₂ did not exhibit the structural ordering of vanadium between the NbS₂ layers. In the ordered structure, the vanadium composition deviated from the ideal value of to both higher and lower values, while the niobium composition was in the range of 0.05?y?0.18. Excess niobium, y>0, is thought to play an essential role in the structural ordering in this system. For samples with excess niobium and ordered structures, a magnetic transition was observed at 20-50 K, depending on the composition. The spontaneous magnetization of 3-5×10⁻³ μ_B/V atom is thought to be intrinsic to this system. The magnetization curves consisted of a constant and a proportional parts of the magnetic field, which correspond to the spontaneous magnetization and high-field susceptibility, respectively. The magnetization curves and the temperature dependencies of the high-field susceptibility were quite similar to those of the canted antiferromagnetic NiS₂. A correlation between the structural and magnetic ordering is suggested.