X-ray photoelectron and X-ray absorption spectroscopic study on β-FeSi2 thin films fabricated by ion beam sputter deposition

A combination of X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) using synchrotron radiation is applied to clarify surface chemical states of β-FeSi₂ films fabricated by an ion-beam sputtering deposition method. The differences in the chemical states of the films fabricated at substrate temperatures of 873, 973 and 1173 K are investigated. For the film fabricated at 873 K, Si 2p XPS spectra indicate the formation of a relatively thicker SiO₂ layer. In addition, Fe L-edge XAS spectra exhibit the formation of FeSi_2−X by preferential oxidation of Si or the presence of unreacted Fe. The results for the film fabricated at 1173 K imply the existence of FeSi₂ with α and ? phases. In contrast, the results for the film fabricated at 973 K indicate the formation of relatively homogeneous β-FeSi₂. These imply that the relatively excellent crystal property of the film fabricated at 973 K is due to the formation of homogeneous β-FeSi₂. As a conclusion, the combination of XPS and XAS using synchrotron radiation is a powerful tool to elucidate the surface chemical states of thin films.     

Asymmetric Suzuki–Miyaura Coupling in Water with a Chiral Palladium Catalyst Supported on an Amphiphilic Resin

You oughta use water : Broad functional‐group (FG) tolerance was observed for the title coupling of aryl halides (X=Cl, Br, I) and aryl boronic acids to give biaryl compounds with up to 94 % ee. The chiral imidazoindole phosphine–palladium catalyst supported on an amphiphilic polystyrene–poly(ethylene glycol) (PS–PEG) resin could be recycled readily.

     

Karatungiols A and B, two novel antimicrobial polyol compounds, from the symbiotic marine dinoflagellate Amphidinium sp.

Karatungiols A (1) and B (2), two novel antimicrobial polyol compounds, were isolated from the cultivated symbiotic marine dinoflagellate Amphidinium sp. Their structures were elucidated based on spectroscopic analysis and degradation reactions. Karatungiols A (1) and B (2) consisted of a C69-linear chain with a ketone moiety, 24 or 25 hydroxyl groups, and two tetrahydropyran rings. Karatungiol A (1) exhibited antifungal activity against Aspergillus niger at 12 μg/disc and antiprotozoan activity against Trichomonas foetus at 1 μg/ml.     

Topographic, electrochemical, and optical images captured using standing approach mode scanning electrochemical/optical microscopy

We developed a high-resolution scanning electrochemical microscope (SECM) for the characterization of various biological materials. Electrode probes were fabricated by Ti/Pt sputtering followed by parylene C-vapor deposition polymerization on the pulled optical fiber or glass capillary. The effective electrode radius estimated from the cyclic voltammogram of ferrocyanide was found to be 35 nm. The optical aperture size was less than 170 nm, which was confirmed from the cross section of the near-field scanning optical microscope (NSOM) image of the quantum dot (QD) particles with diameters in the range of 10-15 nm. The feedback mechanism controlling the probe-sample distance was improved by vertically moving the probe by 0.1-3 microm to reduce the damage to the samples. This feedback mode, defined as "standing approach (STA) mode" (Yamada, H.; Fukumoto, H.; Yokoyama, T.; Koike, T. Anal. Chem. 2005, 77, 1785-1790), has allowed the simultaneous electrochemical and topographic imaging of the axons and cell body of a single PC12 cell under physiological conditions for the first time. STA-mode feedback imaging functions better than tip-sample regulation by the conventionally available AFM. For example, polystyrene beads (diameter approximately 6 microm) was imaged using the STA-mode SECM, whereas imaging was not possible using a conventional AFM instrument.     

Kinetics of OH radical reaction with anthracene and anthracene-d10

Using a refined pulsed laser photolysis/pulsed laser-induced fluorescence (PLP/PLIF) technique, the kinetics of the reaction of a surrogate three-ring polynuclear aromatic hydrocarbons (PAH), anthracene (and its deuterated form), with hydroxyl (OH) radicals was investigated over the temperature range of 373 to 1200 K. This study represents the first examination of the OH kinetics for this class of reactions at elevated temperatures (>470 K). The results indicate a complex temperature dependence similar to that observed for simpler aromatic compounds, e.g., benzene. At low temperatures (373-498 K), the rate measurements exhibited Arrhenius behavior (k = 1.82 x 10(-11) exp(542.35/T) in units of cm3 molecule(-1) s(-1)), and the kinetic isotope effect (KIE) measurements were consistent with an OH-addition mechanism. The low-temperature results are extrapolated to atmospheric temperatures and compared with previous measurements. Rate measurements between 673 and 923 K exhibited a sharp decrease in the magnitude of the rate coefficients (a factor of 9). KIE measurements under these conditions were still consistent with an OH-addition mechanism. The following modified Arrhenius equation is the best fit to our anthracene measurements between 373 and 923 K (in units of cm3 molecule(-1) s(-1)): k(1) (373-923 K) = 8.17 x 10(14) T(-8.3) exp(-3171.71/T). For a limited temperature range between 1000 and 1200 K, the rate measurements exhibited an apparent positive temperature dependence with the following Arrhenius equation, the best fit to the data (in units of cm3 molecule(-1) s(-1)): k1 (999-1200 K) = 2.18 x 10(-11) exp(-1734.11/T). KIE measurements above 999 K were slightly larger than unity but inclusive regarding the mechanism of the reaction. Theoretical calculations of the KIE indicate the mechanism of reaction at these elevated temperatures is dominated by OH addition with H abstraction being a minor contributor.     

Fluorometric determination of fluoride ion by reagent tablets containing 3-hydroxy-2'-sulfoflavone and zirconium(IV) ethylenediamine tetraacetate

A reagent tablet for determination of fluoride ion has been prepared using ethylenediamine-N,N,N′,N′-tetraacetate complex of zirconium (Zr-EDTA), 3-hydroxy-2′-flavone (FS) and an appropriate pH buffer. Dissolving of the tablet into water exhibits an intense blue fluorescence (λ_max = 460 nm) upon excitation at 377 nm and the fluorescence intensity decreases with the presence of fluoride ion. Hence, a simple fluorescent detection procedure for fluoride ion in aqueous media was successfully constructed with this tablet. The principle of this detection system is the ligand exchange reaction of FS bound to Zr-EDTA with fluoride ion. The present system provides an easy, rapid and selective determination method of fluoride ion ranging from 5 × 10⁻⁶ to 1 × 10⁻³ mol dm⁻³. The measurement of real samples with this tablet showed the similar results as those by the common method with the Alfusone reagent.     

Synthesis of bridged nicotinates having [n](2,5)pyridinophane skeletons (n=8-14)

Synthesis of various bridged nicotinates 6 having [n](2,5)pyridinophane skeletons (n=8-14) was accomplished by the unique pyridine-formation reaction of methyl propiolate with a series of formyl-substituted (vinylimino)phosphoranes 5, which were prepared from the corresponding cycloalkanones 1 via Vilsmeier-Haack formylation giving chloro-substituted cycloalkenals 2, their thermal and photochemical transformation to formyl azirines 4, and the following ring-opening reactions with triphenylphosphine. The HPLC analysis of [11](2,5)pyridinophane derivatives, (S_p,S)-14 and (R_p,S)-14, showed that these diastereomers rapidly epimerize themselves at room temperature and that their planar-chirality was thermodynamically less stable as compared to the corresponding [11](2,5)cyclophane systems.     

Conduction electron spin resonance of small silver particles

Electron spin resonance (ESR) spectroscopy has been used to study the conduction electron spin resonance (CESR) of small silver particles stabilized in dehydrated Ag-rho zeolite. Silver particles were produced by hydrogen reduction at elevated temperatures and diameter of the stabilized particles was calculated based on the linewidth of CESR signal using Kawabata theory.     

A new synthesis of 2-sulfanyl allylic alcohols and alpha-sulfanyl ketones from carbonyl compounds and 1-chloroalkyl p-tolyl sulfoxides with carbon-carbon bond-formation

Reaction of lithium alpha-sulfinyl carbanions of 1-chloroalkyl p-tolyl sulfoxides with ketones or aldehydes at low temperature gave adducts in almost quantitative yields. Treatment of the adducts derived from ketones with trifluoroacetic anhydride (TFAA) in the presence of NaI in acetone gave alpha-sulfanyl allylic alcohols in good to quantitative yields. On the other hand, treatment of the adducts derived from aldehydes with TFAA and NaI resulted in the formation of alpha-sulfanyl ketones and/or alpha-sulfanyl allylic alcohols. These reactions offer a good method for the synthesis of the above-mentioned compounds from ketones and aldehydes with carbon-carbon bond-formation in two steps and in good yields.