Mechanism of speckle reduction in laser-microscope images using a rotating optical fiber

The reduction mechanism of speckles appearing in laser-microscope images is studied theoretically and experimentally when an object is illuminated by laser light through a rotating multimode optical fiber. The principle of the speckle reduction is based on independent addition of microscope images with boiling-like speckles as a result of the rotational motion of the optical fiber used for illumination. Especially, the speckle reduction is evaluated from first-order statistics of the speckle intensity in which its saturation effect is taken into consideration.     

Visible light-induced degradation of ethylene glycol on nitrogen-doped TiO2 powders

The photocatalytic degradation processes of ethylene glycol (EG) during the UV or visible light irradiation of pure anatase and nitrogen (N)-doped TiO2 powders (TiO(2-x)N(x), x = 0, 0.002, 0.003, and 0.007) were investigated using time-resolved diffuse reflectance (TDR) and solid-state NMR spectroscopies. The TDR spectra and time traces observed for the charge carriers indicated that the scavenging of photogenerated holes (h+) by EG occurred during the 355-nm laser photolysis of the N-doped TiO2 powders, while no direct oxidation reaction of EG by h+ occurred during the 460-nm laser photolysis, although the charge carriers were sufficiently generated upon excitation. The solid-state magic-angle spinning (MAS) NMR measurements revealed that EG is preferentially chemisorbed on the surface of the N-doped TiO2 powders, in contrast to the pure TiO2, and degrades under visible light irradiation.     

Magnetism of nanographene network influenced by the interaction with acid species

The magnetism of nanographite (stacked nanographene sheets)-based nanoporous carbon is investigated in relation to the interaction with acid guest species. The concentration of the localized spins of non-bonding π-electron state (edge state) localized in the nanographene edges decreases upon the sulfonation of nanographene edges through charge-transfer interaction with sulfonic groups. The sulfonation of nanographene edges enhances the hydrophilic nature of the edges, resulting in the easiness in the water adsorption into the nanopores. This enhances the mechanical compression effect of water molecules condensed in the nanopores on the nanographite domains, resulting in the decrease in the spin concentration. The change in the magnetism upon water uptake reveals ferrimagnetic nature of individual nanographene sheets. The adsorption of HCl having no oxidation ability shows a mechanical effect on the edge-state spins similar to water adsorption. The spin concentration is reduced in two-step manner by the charge-transfer interaction with guest concentrated HNO₃ that is strong oxidant. In the presence of H₂O molecules in diluted HNO₃ the cooperation of mechanical and charge-transfer interactions creates also a two-step change in the magnetism.     

Pt(II)- or Au(III)-catalyzed [3+2] cycloaddition of metal-containing azomethine ylides: highly efficient synthesis of the mitosene skeleton

[reaction: see text] Only 1-3 mol % of PtCl(2) or AuBr(3) was sufficient to promote generation and [3+2] cycloaddition of transition-metal-containing azomethine ylides derived from N-(o-alkynylphenyl)imines bearing an internal alkyne moiety. A highly efficient method for the preparation of synthetically useful tricyclic indole derivatives having a substituent at the 3-position of the indole nucleus was established by this method.     

Photo- and electroluminescence of nitrogen isoelectronic traps in GaAs1–xPx

The variation with temperature of the charge on the surface of NaCl single crystals has been measured directly by means of vibrating capacitor probe. The charge is negative at room temperature, in agreement with theory based on values of the free energy of vacancy formation, decreases with increase of temperature in two stages to a zero value at the isoelectric temperature, and then becomes positive. Values of isoelectric temperature obtained on surfaces are consistent with those obtained by experiments on charged dislocations, which suggests that surfaces could be used to obtain accurate values of the free energy of formation of cation and anion vacancies.     

Discrete π Stack of a Tweezer-Shaped Naphthalenediimide–Anthracene Conjugate

The design and synthesis of a tweezer-shaped naphthalenediimide (NDI)–anthracene conjugate ( 2NDI ) are reported. In the structure of the closed form (π_NDI ⋅⋅⋅ π_NDI stack) of 2NDI , which was elucidated by single-crystal XRD, the existence of C−H ⋅⋅⋅ O hydrogen bonding involving the nearest carbonyl oxygen atom of an NDI unit was suggested. The tunability of π_NDI ⋅⋅⋅ π_NDI interactions was studied by means of UV/Vis absorption, fluorescence and NMR spectroscopy and molecular modelling. This revealed that the π_NDI ⋅⋅⋅ π_NDI interactions in 2NDI affect the absorption and emission properties depending on the temperature. Furthermore, in polar solvents, 2NDI prefers the stronger π_NDI ⋅⋅⋅ π_NDI stack, whereas the π_NDI ⋅⋅⋅ π_NDI interaction is diminished in nonpolar solvents. Importantly, the conformational variations of 2NDI can be reversibly switched by variation in temperature, and this suggests potential application for fluorogenic molecular switches upon temperature changes.     

Iridium‐Catalyzed Sequential Silylation and Borylation of Heteroarenes Based on Regioselective C−H Bond Activation

An iridium‐catalyzed regioselective sequential silylation and borylation of heteroarenes was developed, which represents a rare example of unsymmetrical intermolecular C?H bond difunctionalization through the introduction of two different functionalities during a one‐pot transformation. Although the substrate scope for the dehydrogenative silylation of heteroarenes has been limited mainly to electron‐rich five‐membered rings, the current reaction proceeds with both electron‐rich and electron‐deficient heteroarenes with the aid of heteroatom‐directing C?H bond activation. The regioselectivity of the second borylation was controlled by both steric factors and the electronic effect of the silyl group installed in the first step. In combination with the classic cross‐coupling reaction, this method provides rapid access to multisubstituted heteroarenes.     

Unconventional electronic and magnetic functions of nanographene-based host-guest systems

Nanographene has a unique electronic structure which critically depends on the shape of its edge. A zigzag-edged nanographene sheet has a non-bonding pi-electron state (edge state), yielding a strong spin magnetism for edge-state localized spins, in spite of the absence of such a state in an armchair-edged nanographene sheet. Nanographite (stacked nanographene sheets)-network-based nanoporous carbon is employed as the host material to build unconventional magnetic systems based on the host-guest interaction. The physisorption of various guest materials can cause a reversible low-spin/high-spin magnetic switching phenomenon, whose feature varies depending on the type of guest species. The edge-state spins are utilized as a probe to detect a huge condensation of helium atoms in the nanopores. The giant magnetoresistance of the nanographite network is controlled by the physisorption of magnetic oxygen molecules. The confinement of potassium clusters in the nanopores surrounded by nanographite domains yields an interesting nanomagnetic state. Nanographene/nanographite is an intriguing pi-electron-based nanocarbon material with the potential of producing unconventional magnetic structures that cannot be obtained using bulk graphite. The processability of nanographene/nanographite is expected to give a variety of magnetic functions for spintronic applications.     

Rapid development of hydrophilicity and protein adsorption resistance by polymer surfaces bearing phosphorylcholine and naphthalene groups

In order to provide a protein adsorption resistant surface even when the surface was in contact with a protein solution under completely dry conditions, a new phospholipid copolymer, poly (2-methacryloyloxyethyl phosphorylcholine (MPC)- co-2-vinylnaphthalene (vN)) (PMvN), was synthesized. Poly(ethylene terephthalate) (PET) could be readily coated with PMvN by a solvent evaporation method. Dynamic contact angle measurements with water revealed that the surface was wetted very rapidly and had strong hydrophilic characteristics; moreover, molecular mobility at the surface was extremely low. When the surface came in contact with a plasma protein solution containing bovine serum albumin (BSA), the amounts of the plasma protein adsorbed on the dry surface coated with PMvN and that adsorbed on a dry surface coated with poly(MPC-co-n-butyl methacrylate) (PMB) were compared. Substantially lower protein adsorption was observed with PMvN coating. This is due to the rapid hydration behavior of PMvN. We concluded that PMvN can be used as a functional coating material for medical devices without any wetting pretreatment.