A new model for spectral sensitization of photoconduction in zinc oxide powder

Seven organic dyes were adsorbed on photoconductive zinc oxide powder and their sensitizing efficiencies were examined. The adsorption of dye induced a change in the dark conductivity, the magnitude of which appeared to represent the sensitizing power of the dye. The initial slope of sensitized photocurrent was found to be an exponential function of σ₀, the pre-exponential factor in the conductivity equation. A model is proposed, which is consistent with all the observations. In this model, the sensitized photoinjection of electrons is assumed to occur from surface states to the bulk, depending upon the population of the surface states. A critical surface level for the spectral sensitization is introduced to account for the observed temperature effect. Surface states located below the critical energy are assumed not to contribute for the sensitization.     

Fermi surface of 3d1 perovskite CaVO3 near the Mott transition

We present a detailed de Haas-van Alphen effect study of the perovskite CaVO3, offering an unprecedented test of electronic structure calculations in a 3d transition metal oxide. Our experimental and calculated Fermi surfaces are in good agreement, but only if we ignore large orthorhombic distortions of the cubic perovskite structure. Subtle discrepancies may shed light on an apparent conflict between the low energy properties of CaVO3, which are those of a simple metal, and high energy probes which reveal strong correlations that place CaVO3 on the verge of a metal-insulator transition.     

Reaction mechanism for target-like products from197Au target bombarded with12C ions of energies above 100 MeV/u

Target-like products, that is,^191–200Au,^185–200Pt, and^183–195Ir, from¹⁹⁷Au target bombarded with¹²C ions at the energies of 180, 230, and 400 MeV/u were measured by using off-line gamma-ray spectrometry combined with chemical separation procedures. Spallation systematics by Rudstam reproduces well the measured cross sections for formation of platinum and iridium isotopes. It was found that the cross sections of gold nuclides increase with increase of the incident energy in the range studied and they are enhanced if compared with the reported proton-induced reaction of gold at a similar incident energy. It is suggested that the electromagnetic dissociation process plays a role for production of such gold nuclides.     

Structure and O2-reactivity of copper(I) complexes supported by pyridylalkylamine ligands

The structure and O2-reactivity of a series of copper(I) complexes supported by the pyridylalkylamine ligands are summarized, and the ligand effects such as the chelate ring size effect (five- vs. six-membered ring), the denticity effect (tetradentate vs. tridentate vs. didentate), the steric effect of 6-methylpyridine and the steric and/or electronic effects of N-alkyl substituents are discussed in detail.     

UV absorption and fluorescence properties of fused aromatic hydrocarbons having trimethylsilyl, trimethylgermyl, and trimethylstannyl groups

Effects of trimethylsilyl, trimethylgermyl, and trimethylstannyl substituents attached to fused aromatic hydrocarbons such as pyrene, anthracene, phenanthrene, and naphthalene were studied in terms of UV absorption and fluorescence properties in aerated cyclohexane solutions. Absorption maxima of trimethylsilyl-, trimethylgermyl-, and trimethylstannyl-substituted aromatic hydrocarbons shifted to longer wavelengths than those of unsubstituted ones. Absorption maxima of mono-, bis-, tris-, and tetrakis(trimethylsilyl)pyrenes shifted to longer wavelength consecutively at intervals of 10 nm. Fluorescence intensities and fluorescence lifetimes of trimethylsilyl-substituted aromatic hydrocarbons were larger and longer than those of unsubstituted ones, and they decreased in the order of Me₃SiAr > Me₃GeAr > Me₃SnAr. Fluorescence intensity of 1,3,6,8-tetrakis(trimethylsilyl)pyrene was largest among those of a series of mono-, bis-, tris-, and tetrakis(trimethylsilyl)pyrenes under aerated conditions.     

Electrochemical detection of endotoxin using recombinant factor C zymogen

We have developed a zymogen-based electrochemical sensor. Zymogen is an inactive enzyme precursor (proenzyme) and it is necessary to transform it biochemically (e.g., by hydrolysis and conformational change) to make it an active enzyme. In this study, we demonstrated the detection of endotoxin by using recombinant Factor C (rFC), which is a protease zymogen activated by endotoxin binding. The activated rFC hydrolyzes a synthetic substrate of Boc-Val-Pro-Arg-p-nitroanilnide to generate an electrochemical active compound, p-nitroaniline (pNA). The liberated pNA was detected by differential pulse voltammetry at –0.75 V. By using this electrochemical process, 5000 endotoxin units (EU) L^?1 and 1000 EU L^?1 were detected in a Tris-Ac buffer with a pH of 7.5 at 37 °C for reaction times of 1 h and 3 h, respectively. The concept of zymogen-based electrochemical sensors is expected to lead to the development of new biosensors.     

Reversed-phase partition high-pressure liquid chromatography of trace amounts of inorganic and organic mercury with silver diethyldithiocarbamate

Inorganic and organic mercury diethyldithiocarbamates have been separated by reversedphase partition high-pressure liquid chromatography. The mercury chelates were formed by an exchange reaction with silver diethyldithiocarbamate in chloroform, in the presence of acetate buffer (pH 5.0). The inorganic and organic mercury chelates in the extract were separated within 30 min on a 3.9 x 300 mm mu-Bondapak C(18) column. EDTA (10(-4)M) in methanol-water mixture (78:22 v v ) was used as eluent at a flow-rate of 0.5 ml min .     

Hydrosilylation of alkynes by Ni(CO)3-stabilized silicon(II) hydride

Not copy and paste: Although β-diketiminato ligands have been employed for the stabilization of Ge(II) and Sn(II) hydrides, the corresponding Si(II) hydride is not accessible. However, coordination of silicon(II) to a {Ni(CO)(3)} fragment allowed the isolation of the first Si(II) hydride metal complex 1. This complex was used for the first silicon(II)-based and Ni(0)-mediated, stereoselective hydrosilylation of alkynes. R = phenyl, tolyl.