Quantum Switching of π-Electron Rotations in a Nonplanar Chiral Molecule by Using Linearly Polarized UV Laser Pulses

Nonplanar chiral aromatic molecules are candidates for use as building blocks of multidimensional switching devices because the π electrons can generate ring currents with a variety of directions. We employed (P)-2,2'-biphenol because four patterns of π-electron rotations along the two phenol rings are possible and theoretically determine how quantum switching of the π-electron rotations can be realized. We found that each rotational pattern can be driven by a coherent excitation of two electronic states under two conditions: one is the symmetry of the electronic states and the other is their relative phase. On the basis of the results of quantum dynamics simulations, we propose a quantum control method for sequential switching among the four rotational patterns that can be performed by using ultrashort overlapped pump and dump pulses with properly selected relative phases and photon polarization directions. The results serve as a theoretical basis for the design of confined ultrafast switching of ring currents of nonplanar molecules and further current-induced magnetic fluxes of more sophisticated systems.     

Bartholdi zeta functions of digraphs

We give a determinant expression for the Bartholdi zeta function of a digraph which is not symmetric. This is a generalization of Bartholdi’s result on the Bartholdi zeta function of a graph or a symmetric digraph.     

Chemical activation of cytochrome c proteins via crown ether complexation: cold-active synzymes for enantiomer-selective sulfoxide oxidation in methanol

Supramolecular complexation with 18-crown-6 significantly converted catalytically inactive cytochrome c (biological form) to catalytically active synzyme (artificial form). Although a family of cytochrome c proteins does not work as enzymes in nature, crown ether complexation modified their heme coordination structures and functionally activated them to promote the asymmetric oxidation of racemic sulfoxides at low temperature. Horse heart, pigeon breast, and yeast cytochrome c proteins were demonstrated to form supramolecular complexes with 18-crown-6 in methanol, which effectively oxidized (S)-isomers of naphthyl methyl sulfoxide, methyl tolyl sulfoxide, isopropyl phenyl sulfoxide, benzyl methyl sulfoxide, and 4-methylsulfenyl acetophenone at -40 degrees C. Because horse heart and pigeon breast cytochromes c exhibited more efficient and higher enantiomer-selective activities than yeast cytochrome c, a proper combination of cytochrome c and crown ether offers a new class of cold-active synzymes promoting nonbiological asymmetric oxidation.     

Reaction mechanism of simultaneous catalytic removal of NOx and diesel soot particulates

Reactions of diesel soot and NOx with and without O₂ were carried out over CuFe₂O₄ catalyst. The ignition temperature of soot with the NO+O₂ feed was lower than that in O₂ or NO but close to those in NO₂ and NO₂+O₂, indicating the implication of NO₂ especially in decreasing the ignition temperature. On the other hand, the reduction of NOx into N₂ was enhanced by coexisting O₂. Based on these results and mechanisms of O₂-soot and NO-soot reactions, the possible reaction mechanism of the simultaneous NOx-soot removal with the NO+O₂ feed has been proposed.     

Two-Dimensional Sol-Gel Synthesis of Ultrathin Zirconia and Hetero-Layered Titania/Zirconia Films

Synthesis of ZrO₂ and hetero-layered TiO₂/ZrO₂ ultrathin films was investigated by two-dimensional sol-gel process assisted by n-octadecylacetoacetate (C₁₈AA). When a hexane solution of tetrabutoxyzirconium (TBZ) and C₁₈AA was spread on the water surface, Zr-based gel films stabilized with C₁₈AA were formed at the air/water interface. After deposition on substrates, the gel films were successfully transformed into ZrO₂ ultrathin films by heating at 773 K for 0.5 h, the thickness of which was controllable on the order of sub-nanometer level by the number of gel-layer deposition and the molar ratio of [TBZ]/[C₁₈AA]. Well-organized hetero-multilayers composed of ultrathin TiO₂ and ZrO₂ layers could be fabricated by the alternate deposition of C₁₈AA-stabilized Ti- and Zr-gel films.     

Rapid determination of phenylalanine with immobilized leuconostoc mesenteroides and a lactate electrode

A linear relationship is obtained between current decrease and log (phenylalanine concentration) from 5 × 10^-5 to 10^-7 g ml^-1. The assay was complete in 90 min with a standard deviation of ca. 6%. Phenylalanine was determined accurately in human blood serum.     

Relationship between cation arrangement and photocatalytic activity for Sr-Al-Nb-O double perovskite

The relationship between the photocatalytic activity and the arrangement of metal cations was investigated with Sr-Al-Nb-O double perovskite (SAN) synthesized at 1400 °C for various calcination times using a solid state reaction. Transmission electron microscopic observation revealed that SAN particles had a domain structure of completely B-site ordered (Sr(2)AlNbO(6)) and disordered (SrAl(0.5)Nb(0.5)O(3)) phases. The ordered phase fraction was determined using a newly proposed mixed-phase model for the Rietveld refinement and a method using the relative intensity of the superlattice line of powder X-ray diffraction. It turned out that the mass fraction of the ordered phase in SAN calcined at 1400 °C could be controlled by the calcination time as 33% (10 h), 37% (20 h), 44% (30 h), and 48% (50 h). Photocatalytic activities of SAN for the evolution of H(2) and O(2) respectively from aqueous solutions of methanol and AgF decreased with increasing the calcination time, that is, with increasing the fraction of the ordered phase. These results suggested that the photocatalytic activity of ordered Sr(2)AlNbO(6) should be lower than that of disordered SrAl(0.5)Nb(0.5)O(3). This is practically the first report to reveal the photocatalytic activity of SAN as well as the effect of cation ordering in oxides on the photocatalytic activity.