Selective fabrication of n‐ and p‐type SnO films without doping

Undoped n‐ and p‐type tin monoxide (SnO) films have been selectively fabricated by pulsed laser deposition with a Sn target and careful control of oxygen partial pressure. The films are epitaxially grown in optimal growth conditions on yttria‐stabilized zirconia (YSZ) substrates with out‐of‐plane and in‐plane orientation relationships of (001)_SnO//(001)_YSZ and [110]_SnO//[100]_YSZ, respectively. Both Seebeck and Hall measurements show consistent results on the carrier types of the films. The electron Hall mobility is approximately 11 cm²/Vs at room temperature and the carrier activation energy is 0.14 eV for the n‐type film. The growth at increased oxygen partial pressure yields p‐type films, demonstrating the selective fabrication of both n‐ and p‐type SnO films without doping. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Large fullerenes in mass spectra

Fullerenes have been studied for nearly three decades and enormous advances have been made. Mass spectrometry is commonly used for investigations on the distribution of fullerenes formed from evaporated graphite targets, and soot produced from such targets. We report distributions of fullerenes formed by graphite evaporation by use of a pulsed supersonic cluster source and compare them to certain distributions synthesised by other techniques, such as arc discharge and combustion methods. We highlight the fact that physical processes can occur during the mass spectral analysis of fullerenes under certain conditions that may skew the observed distribution of cage sizes present in a sample. In some cases, an analysis of fullerene-containing soot can greatly exaggerate the relative abundance of large fullerenes compared to C₆₀ and medium-sized fullerenes, depending on the particular experimental setup.     

Synergistic cascade catalysis by metal nanoparticles and Lewis acids in hydrogen autotransfer

Of the many types of catalysis involving two or more catalysts, synergistic catalysis is of great interest because novel reactions or reaction pathways may be discovered when there is synergy between the catalysts. Herein, we describe a synergistic cascade catalysis, in which immobilized Au/Pd bimetallic nanoparticles and Lewis acids work in tandem to achieve the N-alkylation of primary amides to secondary amides with alcohols via hydrogen autotransfer. When Au/Pd nanoparticles were used with metal triflates, a significant rate acceleration was observed, and the desired secondary amides were obtained in excellent yields. The metal triflate is thought to not only facilitate the addition of primary amides to aldehydes generated in situ, but also enhance the returning of hydrogen from nanoparticles to hydrogen-accepting intermediates. This resulted in a more rapid turnover of the nanoparticle catalyst, and ultimately translated into an increase in the overall rate of the reaction. The two catalysts in this co-catalytic system work in a synergistic and cascade fashion, resulting in an efficient hydrogen autotransfer process.     

“Click” Incorporation of Radical/Ionic Sites into a Reactive Block Copolymer: A Facile and On‐Demand Domain Functionalization Approach toward Organic Resistive Memory

Reversible addition‐fragmentation chain transfer polymerization yields reactive block copolymers bearing the pentafluorophenyl ester (PFPA) group, and subsequent Click amidation using 2,2,6,6‐tetramethylpiperidine‐N‐oxyl‐ and imidazolium‐functionalized primary amines produces the corresponding functional block copolymers, leading to installation of statistical radical‐ and ionic sites into the PFPA segment. The monolayered thin film devices fabricated using the obtained block copolymers exhibit repeatable switching of electric conductivity (on/off ratio > 10³) under a bias voltage, which reveals that the coexistence of radicals and ions in the same spherical domain of the copolymer layer is a prerequisite for repeatable switching memory.

     

A novel impact three-point bend test method for determining dynamic fracture-initiation toughness

A novel impact three-point bend test method has been developed for determining the dynamic fracture-initiation toughness,K _Id, over the range of loading rates . The split-Hopkinson pressure-bar technique is used to measure dynamic loads applied to a bend specimen with a fatigue precrack. The stress-intensity-factor histories for the bend specimen are evaluated by means of a dynamic finite-element technique and the standard formula (ASTM E 399-83) based on the measured dynamic loads. The time of crack initiation is determined using a strain gage mounted near a crack tip. The results for 7075-T6 aluminum alloy and Ti−6A1−2Sn−4Zr−6Mo alloy indicate that the reliableK _Id data can only be obtained by evaluation procedures which take the inertial effects into account. It is shown that the novel impact bend test method in conjunction with dynamic finite-element analysis provides an effective means of characterizing the dynamic fracture-toughness parameterK _Id.     

Syntheses and characterization of two copper pyridine-dicarboxylate compounds containing water clusters

A new homonuclear and heterodinuclear pyridine-2,6-dicarboxylate complexes, formulated as (enH₂)[Cu(dipic)₂]·2.5H₂O (1) and [Cu(μ-dipic)₂Zn(H₂O)₅]·2H₂O (2) (en = ethylenediamine, dipic = pyridine-2,6-dicarboxylate) were synthesized according the reactions between the three species of copper(II) and zinc(II) nitrate, ethylenediamine and pyridine-2,6-dicarboxylic acid. Complexes have been characterized by the methods of elemental, spectroscopic (IR and UV–Vis), thermal (TG/DTG, DTA) analysis, magnetic measurement and single crystal X-ray diffraction. Correlation coefficient, activation energies, E∗; pre-exponential factor, A; entropies, S∗; enthalpies, H∗ and Gibbs free energies, G∗ of the thermal decomposition reactions have been calculated under the derivations from thermogravimetric (TG) and differential thermogravimetric (DTG) curves, using the Coats–Redfern and Horowitz–Metzger methods. Complex 1 belonged to a six-coordinate behavior with a distorted octahedral geometry around Cu(II), that the structure contains two pyridine-2,6-dicarboxylate species as a tridentate ligands and ethylenediaminium cation as a counter ion as well as 2.5 uncoordinated water molecules. On the other hand complex 2 contains six-coordinated Cu(II) and Zn(II) ions, which are linked by two O atoms of the same carboxyl group from dipicolinic acid. The dipicolinate dianions again behave as tridentate ligands in 2. Two uncoordinated water molecules are also present in the structure. The structure units of 1 and 2 are mutually held by the hydrogen bonds and π?π interactions. There is also a C–O?π interaction in 2. The Cu(II) complexes are connected to one another via O–H?O hydrogen bonds, forming water clusters, which play an important role in the stabilization of the crystal structure. In the water clusters, the water molecules are trapped by the cooperative association of coordination interactions as well as hydrogen bonds.     

Preparation of new nitrogen-bridged heterocycles 72. A new approach to 1-acyl-3-(substituted methylthio)thieno[3',4':4,5]imidazo[1,2-a]pyridine derivatives. [corrected

The alkaline treatment of the pyridinium salts, readily available from the S-alkylations of 3-amino-4-(1-pyridinio)thiophene-5-thiolates with various alkyl halides, in chloroform at room temperature afforded the corresponding thieno[3',4':4,5]imidazo[1,2-a]pyridine derivatives in low to moderate yields via the intramolecular cyclization of the resulting 1,5-dipoles followed by the aromatization of the primary cycloadducts. Interestingly, the reactions using unsymmetrical 3-amino-4-[1-(3-methylpyridinio)]thiophene-5-thiolates afforded only 8-methylthieno[3',4':4,5]imidazo[1,2-a]pyridines and the other 6-methyl derivatives were not formed at all. In addition the isolation of a byproduct in the condensation reaction of pyridinium salt with the solvent (CHCl?) is also discussed.     

A Simple Fabrication Method for Three‐Dimensional Gold Nanoparticle Electrodes and Their Application to the Study of the Direct Electrochemistry of Cytochrome c

A simple method for constructing gold nanoparticle‐modified electrodes with three‐dimensional nanostructures is demonstrated. The electrodes were prepared by casting citrate‐reduced AuNPs onto polycrystalline gold electrodes. The resultant electrodes had a large surface area‐to‐volume ratio, adequate for high protein loading and conferring high stability. The gold nanoparticle electrodes were covered with a self‐assembled monolayer of 11‐mercaptoundecanoic acid for electrostatic immobilization of cytochrome c (cyt c). At the electrode, direct, reversible electron transfer from cyt c was observed with remarkable stability. Moreover, an extremely high surface coverage of electrochemically active cyt c, 167 fully packed monolayers, was obtained through use of the electrode.     

Flavour mixing of neutrinos and baryon asymmetry of the universe

We investigate baryogenesis in the ν  MSM, which is the Minimal Standard Model (MSM) extended by three right-handed neutrinos with Majorana masses smaller than the weak scale. In this model the baryon asymmetry of the universe (BAU) is generated via flavour oscillation between right-handed neutrinos. We consider the case when BAU is solely originated from the CP violation in the mixing matrix of active neutrinos. We perform analytical and numerical estimations of the yield of BAU, and show how BAU depends on mixing angles and CP violating phases. It is found that the asymmetry in the inverted hierarchy for neutrino masses receives a suppression factor of about 4% comparing with the normal hierarchy case. It is, however, pointed out that, when θ₁₃=0${\theta }_{13}=0$ and θ₂₃=π/4${\theta }_{23}=\pi /4$, baryogenesis in the normal hierarchy becomes ineffective, and hence the inverted hierarchy case becomes significant to account for the present BAU.