Analysis of electronic structures of 3d transition metal-doped TiO2 based on band calculations

The electronic structures of titanium dioxide (TiO₂) doped with 3d transition metals (V, Cr, Mn, Fe, Co and Ni) have been analyzed by ab initio band calculations based on the density functional theory with the full-potential linearized-augmented-plane-wave method. When TiO₂ is doped with V, Cr, Mn, Fe, or Co, an electron occupied level occurs and the electrons are localized around each dopant. As the atomic number of the dopant increases the localized level shifts to lower energy. The energy of the localized level due to Co is sufficiently low to lie at the top of the valence band while the other metals produce midgap states. In contrast, the electrons from the Ni dopant are somewhat delocalized, thus significantly contributing to the formation of the valence band with the O p and Ti 3d electrons. Based on a comparison with the absorption and photoconductivity data previously reported, we show that the t_2g state of the dopant plays a significant role in the photoresponse of TiO₂ under visible light irradiation.     

Salt-catalyzed addition reaction of monoepoxides with philosamia cynthia ricini and bombyx mori silk fibroins

The heterogeneous addition reaction of various monoepoxides with silk fibroins of Philosamia cynthia ricini and Bombyx mori was investigated at 45–75°C by use of aqueous solutions of various salts as padding catalysts. The effects of salt on the epoxide–silk fibroin reactions were attributed mainly to the nucleophilicity of the anions and also to the acidity or the electronegativity of the cations. The effect of the substituent of the epoxide on the add-ons was elucidated by the modified Taft equation, (log W ? log W₀)/σ* = ρ_p + ρ_sE_s/σ*, where W₀ and W are the add-ons for the reaction of a given compound and of its substituted derivatives, σ* and E_s are the polar and the steric substituent constants, ρ_p and ρ_s are the polar and the steric reaction constants, respectively. Histidine, lysine, arginine, tyrosine, serine, and acidic amino acids were found to react. The reactivity difference between Philosamia cynthia ricini and Bombyx mori fibroins towards the epoxide was discussed in the light of the observed phenomena.     

Colorimetric detection of fluoride ion in an aqueous solution using a thioglucose-capped gold nanoparticle

The thioglucose-capped gold nanoparticles have been prepared by the chemical reduction of HAuCl₄ using thioglucose as the reducing and capping agent, which displays selective colorimetric detection of fluoride ion in 10 mM HEPES buffer at physiological pH.     

Preparation and electrochemical properties of palladium(0) complexes coordinated by quinones and 1,5-cyclooctadiene

The complexes Pd(quinone)(COD) (COD = 1,5-cyclooctadiene) are prepared by a ligand substitution reaction of Pd₂(DBA)₃ (DBA = dibenzylideneacetone) in the presence of both quinone and COD. Palladium(0) complexes coordinated by quinones only are formed in the reaction in the absence of COD. The cyclic voltammetric behavior of Pd(quinone)(COD) has been studied. The reduction potentials for quinones shifted toward negative values on coordination to palladium(0). The oxidation potentials for the central palladium(0) in Pd(quinone)(COD) depend on the electron-withdrawing ability of the free quinones, and are in the following series: quinone = p-benzoquinone < 5,8-dihydro-1,4-naphthoquinone ～ 1,4-naphthoquinone < duroquinone. The shift of oxidation potentials for Pd(quinone)(COD) on changing the quinones as ligands is in contrast to that of Pd(quinone)(triphenylphosphine)₂.     

Photocatalytic H2 evolution under visible-light irradiation over band-structure-controlled (CuIn)xZn2(1-x)S2 solid solutions

(CuIn)(x)Zn2(1-x)S2 solid solutions between a ZnS photocatalyst with a wide band gap and CuInS(2) with a narrow band gap showed photocatalytic activities for H(2) evolution from aqueous solutions containing sacrificial reagents SO(3)(2-) and S(2-) under visible-light irradiation (lambda >/= 420 nm). Pt (0.5 wt %)-loaded (CuIn)(0.09)Zn(1.82)S(2) with a 2.3-eV band gap showed the highest activity for H(2) evolution, and the apparent quantum yield at 420 nm amounted to 12.5%. H(2) evolved at a rate of 1.5 L h(-1) m(-2) under irradiation with a solar simulator (AM 1.5). Diffuse reflection and photoluminescence spectra of the solid solutions shifted monotonically to a long wavelength side, as the ratio of CuInS(2) to ZnS increased in the solid solutions. The photocatalytic H(2) evolution depended on the composition as well as the photophysical properties. DFT calculations suggested that the visible-light response should be derived from the contribution of Cu 3d and S 3p orbitals to the valence band and that of In 5s5p and Zn 4s4p orbitals to the conduction band, respectively. The contribution of these orbitals to the energy bands affected the photophysical and photocatalytic properties.     

Two new pregnane glycosides from Dioscorea futschauensis R. KUNTH

Two new pregnane glycosides (1, 2) together with two known saponins were isolated from the rhizomes of Dioscorea futschauensis R. KUNTH. The structures of 1 and 2 were established as 16alpha-methoxyl-3beta-[(O-alpha-L-rhamnopyranosyl-(1-->2)-O-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucopyranosyl)oxy]pregn-5-en-20-one and 21-methoxyl-3beta-[(O-alpha-L-rhamnopyranosyl-(1-->2)-O-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucopyranosyl)oxy]pregn-5,16-en-20-one, respectively, on the basis of two-dimension NMR (2D NMR) and other spectral analysis. Their in vitro bioactivity against plant pathogenic fungus Pyricularia oryzae and osteoblastic proliferation stimulatory activity in the UMR106 cell line were evaluated.     

Magnetic field effects on microstructural variation of electrodeposited cobalt films

The electrodeposition process of Co films in a sulfuric acid solution was examined in a magnetic field (0–5 T). The surface morphology of Co films electrodeposited without a magnetic field was drastically modified with the variation of hydrogen gas evolution rate. Crystalline α-Co was formed in the range of pH = 1.5–6.0, while β-Co was not observed. When the magnetic field was superimposed perpendicular to the electric field in the acidic solution (pH = 1.5), the hydrogen evolution rate was promoted by MHD convection, which enhanced the ionic mass transfer (H⁺ and Co²⁺) near the electrode surface. Moreover, crystalline β-Co was formed simultaneously with the appearance of the elongated ridge-shape precipitates under a higher magnetic field (≥3 T). Contribution to special issue “Magnetic field effects in Electrochemistry”     

Momentum density and molecular geometry. Bent BH 2 − and linear BH 2 +

Based on a special form of the molecular virial theorem, the recently proposed method of momentum density for interatomic interactions is here applied to the problem of molecular geometry. Two molecules BH ₂ ^– and BH ₂ ⁺ , which have the same nuclear framework but favor respectively bent and linear conformations, are comparatively studied. Using an approximate Hartree-Fock momentum density, the total molecular energy (including the nuclear repulsion) is partitioned into orbital components, and a geometry correlation diagram is derived. An atom-bond partitioning of the total energy is also examined based on the one- and two-center decomposition of the momentum density.     

An integrated strategy by absorbed component characterization,pharmacokinetics, and activity evaluation for identification of potential nephroprotective substances in Zhu-Ling decoction

An efficient strategy for the identification of potential nephroprotective substances in Zhu-Ling decoction has been established with the integration of absorbed components characterization, pharmacokinetics, and activity evaluation. A qualitative method was developed to characterize the chemical constituents absorbed components in vivo of Zhu-Ling decoction by using ultra-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry. A quantitative method was established and validated for the simultaneous determination of eight compounds in rat plasma by using ultra-performance liquid chromatography-triple quadruple tandem mass spectrometry. Finally, the nephroprotective activities of absorbed components with high exposure were assessed by cell survival rate, superoxide dismutase, and malondialdehyde activities in hydrogen peroxide–induced Vero cells. As a result, 111 compounds in Zhu-Ling decoction and 36 absorbed components were identified in rat plasma and urine, and poricoic acid A, poricoic acid B, alisol A, 16-oxo-alisol A, and dehydro-tumulosic acid had high exposure levels in rat plasma. Finally, poricoic acid B, poricoic acid A, 16-oxo-alisol A, and dehydro-tumulosic acid showed remarkable nephroprotective activity against Vero cells damage induced by hydrogen peroxide. Besides, superoxide dismutase and malondialdehyde activities were obviously regulated in hydrogen peroxide–induced Vero cells by treatment with the four compounds mentioned above. Therefore, these four compounds were considered to be effective substances of Zhu-Ling decoction due to their relatively high exposure in vivo and biological activity. This study provided a chemical basis for the action mechanism of Zhu-Ling decoction in the treatment of chronic kidney diseases.     

Electronic data acquisition and operational control system for time-of-flight sputtered neutral mass spectrometer

A new electric data acquisition and operational control system was developed for time-of-flight sputtered neutral mass spectrometry (TOF-SNMS). The system is designed for high-speed data acquisition, data processing, and data streaming. The developed system is constructed on an NI-PXI platform and provides timing clocks for the TOF-SNMS operation. The system performs data processing of noise suppression and ion counting while acquiring TOF mass spectrum for 13-microsecond length at sampling rate of 3 GS/s for every 1 millisecond. In addition, the system acquires and records TOF mass spectrum of 60-microsecond length at sampling rate of 3 GS/s for every 1 millisecond without data processing. The system detects single ion signals from accumulated TOF mass spectrum of 10⁷ times and counts up to 10 ions accurately from a single event of TOF mass spectrum.