Stabilization of High‐Valence Ruthenium with Silicotungstate Ligands: Preparation,Structural Characterization,and Redox Studies of Ruthenium(III)‐Substituted α‐Keggin‐Type Silicotungstates with Pyridine Ligands, [SiW11O39RuIII(Py)]5−

Ruthenium(III)‐substituted α‐Keggin‐type silicotungstates with pyridine‐based ligands, [SiW₁₁O₃₉Ru^III(Py)]^5?, (Py: pyridine ( 1 ), 4‐pyridine‐carboxylic acid ( 2 ), 4,4′‐bipyridine ( 3 ), 4‐pyridine‐acetamide ( 4 ), and 4‐pyridine‐methanol ( 5 )) were prepared by reacting [SiW₁₁O₃₉Ru^III(H₂O)]^5? with the pyridine derivatives in water at 80 °C and then isolated as their hydrated cesium salts. These compounds were characterized using cyclic voltammetry (CV), UV/Vis, IR, and ¹H NMR spectroscopy, elemental analysis, titration, and X‐ray absorption near‐edge structure (XANES) analysis (Ru K‐edge and L₃‐edge). Single‐crystal X‐ray analysis of compounds 2 , 3 , and 4 revealed that Ru^III was incorporated in the α‐Keggin framework and was coordinated by pyridine derivatives through a Ru? N bond. In the solid state, compounds 2 and 3 formed a dimer through π? π interaction of the pyridine moieties, whereas they existed as monomers in solution. CV indicated that the incorporated Ru^III–Py was reversibly oxidized into the Ru^IV–Py derivative and reduced into the Ru^II–Py derivative.     

Inter-subband optical absorption in space-charge layers on semiconductor surfaces

The resonance energy and the lineshape of absorption for inter-subband transitions are calculated in an approximation scheme based on the density-functional formulation inn-channel accumulation and inversion layers on the (100) surface of Si. The exciton-like effect almost cancels the resonance screening (depolarization) effect found recently by Allen et al., and the resonance energy is rather close to subband energy-separation. The agreement between the theory and experiments is satisfactory both for the resonance energy and for the lineshape. The theory is applied to accumulation layers on the (111) and (110) surface, and explains characteristic change of the lineshape observed experimentally.A research fellow of the Allexander von Humboldt Foundation     

Estimation of the Refractive Index Change in Glass Induced by Femtosecond Laser Pulses

It is known that local refractive index change occurs when femtosecond laser pulses with extremely high peak power are launched into glass. We focused 130-femtosecond laser pulses of 800 nm into the bulk of glass and examined the shape of the induced refractive index change. We found that the length of the spot of the refractive index change along the optical axis reached about 30 μm despite the diameter being about 2 μm. To estimate the distribution of induced refractive index change, we fabricated Bragg grating by scanning the focused spot and calculated the amount of the change by applying Kogelnik’s coupled mode theory to the measured diffraction efficiencies of the higher order diffracted beams.     

Approximating Solutions of Maximal Monotone Operators in Hilbert Spaces

Let H be a real Hilbert space and let T: H→2^H be a maximal monotone operator. In this paper, we first introduce two algorithms of approximating solutions of maximal monotone operators. One of them is to generate a strongly convergent sequence with limit vT⁻¹0. The other is to discuss the weak convergence of the proximal point algorithm. Next, using these results, we consider the problem of finding a minimizer of a convex function. Our methods are motivated by Halpern's iteration and Mann's iteration.     

Size-selected copper oxide nanoparticles synthesized by laser ablation

Size-tuned copper oxide nanoparticles with sizes of 9, 12, and 15 nm were fabricated by laser ablation and on-line size selection using a differential mobility analyzer at a gas pressure of 666 Pa. The dependence of the particle properties on the in situ annealing temperatures and selection sizes was investigated. The crystalline phases of the nanoparticles fabricated at temperatures below 973 K were assigned to monoclinic cupric oxide (CuO) which converted into cubic cuprous oxide (Cu₂O) when the annealing temperature was above 1,173 K. This indicates that the crystalline phases can be easily controlled by changing the annealing temperature. TEM images confirmed that well-crystallized and well-dispersed CuO and Cu₂O nanoparticles with narrow size distributions were obtained using this method. This fabrication process is useful and promising for the future investigation of the intrinsic size-dependent properties of CuO and Cu₂O.     

Preparation of thermo- and redox-responsive branched polymers composed of three-armed oligo(ethylene glycol)

We herein report the preparation of thermo- and redox-responsive branched polymers by the condensation reaction of three-armed oligo(ethylene glycol) (trisOEG) and cystamine (CA). The prepared branched polymers exhibited a soluble–insoluble transition at a lower critical solution temperature (LCST) and formed coacervate droplets through a liquid–liquid phase separation process. We then demonstrated control of the LCSTs of the branched polymers by varying the feed ratio of CA and the surrounding salt concentration close to body temperature. In addition, the trisOEG-cys _x polymer formed coacervate droplets above the LCST, in which hydrophobic molecules were condensed. The redox response of the branched polymers was also investigated. Interestingly, the branched polymers degraded to low-molecular-weight materials (i.e., trisOEG) in the presence of dithiothereitol as a reducing agent through cleavage of the disulfide bond of CA. This facile preparation of branched polymers is expected to be valuable in the context of functional biomedical materials and modifiers for materials surfaces, such as the bases for drug delivery carriers and separation materials. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2623–2629