Molecular dynamics simulations of structural disordering and forming defects in a milling process for selenium

In our previous paper, structural changes of selenium powders ground by a planetary ball mill at various rotational speeds were investigated for the nanostructural modification of particles using mechanical grinding process. The experimental results indicated that the amorphisation of Se by grinding accompanies lattice strain, and the lattice strain arises from impact energy which is more than an energy related to intermolecular interaction. In this paper, molecular dynamics simulations of selenium have been carried out under compressing conditions of various pressure strengths for obtaining information of the lattice strain at atomic level. Then, dynamical behaviour of atomic configuration has been discussed in this process. The structural disordering and formation of the structural defects were estimated by deviations of bond length and angle and the number of created defects before and after compressing from simulated results. The disordering took place during compressing at various pressure strengths, and the disordered atoms return to their initial positions at lower pressure. Stable disordered state and defects after the compression can however remain by compression at more than a certain pressure strength mainly associated with binding energy of selenium.     

Mössbauer study of the fraction of non-bridging oxygens in potassium borate glasses

A Mössbauer study was performed to find the fraction of non-bridging oxygens in potassium borate glasses containing a small amount of iron. The borate glasses with alkali contents of 15, 20, 25, 30 and 40 mol% were irradiated with ⁶⁰Co-γ rays at room temperature in a nitrogen atmosphere. The Mössbauer absorption area for the irradiation-induced Fe²⁺ increased with the total γ-ray dose in the range of 1 × 10⁶ ?2 × 10⁸ R, and became constant after irradiation ranging from 2 × 10⁸ R ? 1 × 10⁹ R. The absorption area for the Fe²⁺ at the saturated region was correlated with the difference in the glass structure, i.e., the fraction of the non-bridging oxygens was estimated from the increased absorption area for the Fe²⁺ as a function of the alkali content of the glasses. The fraction of the non-bridging oxygen increased with the alkali content of the glasses in the alkali region above 20 mol%, and about 14% of the fraction was obtained for an alkali content of 40 mol%.     

Substituent effects of iridium complexes for highly efficient red OLEDs

This study reports substituent effects of iridium complexes with 1-phenylisoquinoline ligands. The emission spectra and phosphorescence quantum yields of the complexes differ from that of tris(1-phenylisoquinolinato-C2,N)iridium(iii)(Irpiq) depending on the substituents. The maximum emission peak, quantum yield and lifetime of those complexes ranged from 598-635 nm, 0.17-0.32 and 1.07-2.34 micros, respectively. This indicates the nature of the substituents has a significant influence on the kinetics of the excited-state decay. The substituents attached to phenyl ring have an influence on a stability of the HOMO. Furthermore, those substituents have effect on the contribution to a mixing between 3pi-pi* and (3)MLCT for the lowest excited states. Some of the complexes display the larger quantum yield than Irpiq, which has the quantum yield of 0.22. The organic light emitting diode (OLED) device based on tris [1-(4-fluoro-5-methylphenyl)isoquinolinato-C2,N]iridium(iii)(Ir4F5Mpiq) yielded high external quantum efficiency of 15.5% and a power efficiency of 12.4 lm W(-1) at a luminance of 218 cd m(-2). An emission color of the device was close to an NTSC specification with CIE chromaticity characteristics of (0.66, 0.34).     

Texture in the superconducting order parameter of CeCoIn5 revealed by nuclear magnetic resonance

We present a 115In NMR study of the quasi-two-dimensional heavy-fermion superconductor CeCoIn5 believed to host a Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state. In the vicinity of the upper critical field and with a magnetic field applied parallel to the ab plane, the NMR spectrum exhibits a dramatic change below T*(H) which well coincides with the position of reported anomalies in specific heat and ultrasound velocity. We argue that our results provide the first microscopic evidence for the occurrence of a spatially modulated superconducting order parameter expected in a FFLO state. The NMR spectrum also implies an anomalous electronic structure of vortex cores.     

A novel dinuclear cyclometalated iridium complex bridged with 1,4-bis[pyridine-2-yl]benzene: its structure and photophysical properties

The synthesis, structure, and photophysical properties of a new cyclometalated dinuclear iridium complex, (ppy)2Ir(mu-BPB)Ir(ppy)2 [ppy = 2-phenylpyridine, BPB = 1,4-bis(pyridin-2-yl)benzene], have been investigated.     

Supramolecular nanocarrier of siRNA from PEG-based block catiomer carrying diamine side chain with distinctive pKa directed to enhance intracellular gene silencing

An siRNA nanocarrier formed through self-assembly of PEG-based block catiomer possessing two distinct amino groups with different pKa values in a side chain was developed. This design provided the carrier with a sufficient siRNA complexation and an assumed buffering capacity in the endosomes, allowing it to exhibit remarkable gene knockdown abilities as well as sufficient serum tolerability.     

Ni-catalyzed, ZnCl(2)-assisted domino coupling of enones, alkynes, and alkenes

A Ni(0)/ZnCl(2) system effectively promotes the coupling of enones and alkene-tethered alkynes. In the reaction with 1,6-enynes, the oxidative cyclization of Ni(0) species on enones across the alkyne part followed by ZnCl(2)-promoted cleavage generates alkenylnickel intermediates. Subsequent migratory insertion of the tethered alkene occurs with 5-exo-cyclization. When the resulting sigma-alkylnickel intermediates have beta-hydrogen atoms, the reaction terminates by beta-hydrogen elimination to provide cyclopentane derivatives. On the other hand, a sigma-alkylnickel intermediate that does not have beta-hydrogen atoms undergoes the insertion of a second alkene unit to cause a domino effect via a three-fold C-C bond formation process with and without the cleavage of one C-C bond.